24M Manual

SERV1844November 2007

TECHNICAL PRESENTATION

24M MOTOR GRADERINTRODUCTION

Service Training Meeting Guide(STMG)

GLOBAL SERVICE LEARNING

24M MOTOR GRADER - INTRODUCTION

AUDIENCE

Level II - Service personnel who understands the principles of machine system operation,diagnostic equipment, and procedures for testing and adjusting.

CONTENT

This presentation provides information on the system operation of the electrical system,operator’s station, engine, power train, implement, steering, fan, and brake systems. Thispresentation may be used for self-paced and self-directed training.

OBJECTIVESAfter learning the information in this meeting guide, the technician will be able to:

1. locate and identify the major components in the electrical system, operator’s station,engine, power train, implement, steering, fan, and brake systems

2. explain the operation of the major components in the systems

3. trace the flow of oil through the systems

PREREQUISITES

"Fundamentals of Engines Self Study Course" TEMV3001"Fundamentals of Mobile Hydraulics Self Study Course" TEMV3002"Fundamentals of Power Trains Self Study Course" TEMV3003"Fundamentals of Electrical Systems Self Study Course" TEMV3004STMG546 "Graphic Fluid Power Symbols" SESV1546

Estimated Time: 36 HoursIllustrations: 153Form: SERV1844Date: 11/07

© 2007 Caterpillar Inc.

TABLE OF CONTENTS

INTRODUCTION ........................................................................................................................5

OPERATOR'S STATION..............................................................................................................7

MESSENGER.............................................................................................................................22Messenger Main Menu .........................................................................................................22Performance Menu Options..................................................................................................23Totals Menu Options.............................................................................................................25Settings Menu Options .........................................................................................................27Service Menu Options ..........................................................................................................29

ECM ARCHITECTURE ............................................................................................................35

C18 ACERT™ ENGINE ............................................................................................................37Engine Electronic Control System Block Diagram..............................................................38Fuel System Block Diagram.................................................................................................41Engine Compartment Locations ...........................................................................................43Engine Idle Management......................................................................................................70Engine Brake.........................................................................................................................71

POWER TRAIN .........................................................................................................................80Transmission/Chassis Electrical System ..............................................................................83Power Train Hydraulic System.............................................................................................96Differential Lock.................................................................................................................118

IMPLEMENT AND STEERING SYSTEM ............................................................................121Implement Electrical System..............................................................................................124Left Joystick Electronic Operation .....................................................................................127Right Joystick Electronic Operation...................................................................................129Steering Hydraulic System Operation ................................................................................144Implement and Steering System Components....................................................................148Implement Hydraulic System Operation ............................................................................156Variable Float Control.........................................................................................................161

BRAKE AND FAN SYSTEM..................................................................................................165Service Brake Valve - Not Activated..................................................................................169Service Brake Valve - Activated.........................................................................................170Brake and Fan System Hydraulic Operation......................................................................177Parking Brake System.........................................................................................................183Fan System..........................................................................................................................187

CONCLUSION.........................................................................................................................189

SERV1844 - 3 - Text Reference11/07

TABLE OF CONTENTS

HYDRAULIC SCHEMATIC COLOR CODE.........................................................................190

VISUAL LIST ..........................................................................................................................191


INTRODUCTION

The 24M Motor Grader has been designed as a direct replacement for the 24H Motor Grader.The 24M meets U.S Environmental Protection Agency (EPA) Tier 3 and European Union StageIIIa emissions control standards.

Key new features include:

- Improved operator's station

- C18 ACERT™ Engine

- ECPC controlled power shift transmission

- Joystick steering

- Electro-hydraulic steering

- Electro-hydraulic implements

- Hydraulic braking system

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24M MOTOR GRADERSINTRODUCTION

© 2007 Caterpillar Inc.

Technical Specifications

24M- Serial number prefix: B9K

- Base machine weight: 62,456 kg (137,692 lb)

- Max machine weight: 66,128 kg (145,808 lb)

- Max ground speed forward: 43 km/h (26.7 mph)

- Max ground speed reverse: 41.2 km/h (25.6 mph)

- Engine: C18 ACERT™

- Net power with VHP: 397 kW (533 hp)

- Net power with VHP Plus: 103-129 kW (138-173 hp)

- Derating Altitude: 3353 m (11,000 ft)

- Length: 14.2 m (28 ft)

- Width: 4.3 m (8 ft)

- Height: 4.4 m (11 ft)


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OPERATOR'S STATION

The redesigned operator's station provides better visibility to the work area. The "M" seriesoperator's station also has new features and improvements over the H series.

The main components in the operator's station are:

- Instrument cluster (1)- Left electronic joystick (2)- Right electronic joystick (3)- Messenger display panel (4)- Cab switch panel (5)- Wiper/washer switches (6)- Radio (if equipped, 7)- Variable float switch panel (8)- Service brake pedal (9)- Accelerator pedal (10)- Ripper control lever (11)


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The instrument cluster contains the following:

- Coolant temperature gauge (1)

- Hydraulic oil temp gauge (2)

- Tachometer (3)

- Articulation angle (4)

- Fuel gauge (5)

When the key start switch is turned to the ON position, the dash cluster will perform a threesecond self-test. During this test all alert indicators will illuminate, and the gauges will do asingle sweep.

Sometimes the data needed for an indicator is unknown. This can be due to data linkcommunication problems or active sensor diagnostics. Effects of unknown data at the dashcluster are as follows:

- When data needed for an indicator is unknown the indicator will be illuminated.

- When data needed for a gauge is unknown the gauge will be driven to its red zone.

- When data needed for the LCD is unknown the LCD will either be blank or display "---."

- When there is a Messenger to dash cluster communication problem all indicators will beoff, all gauges will point to the left, and the action lamp will blink amber.

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The "M" series dash cluster contains the following indicators, starting at the left side:

- Left turn indicator: Illuminates when the left turn signal is operating.

- Left blade float indicator: Illuminates when the left blade control valve is in the floatposition.

- Charging system indicator: Illuminates when there is a problem with the charging system.

- Starting aid indicator: Illuminates when the starting aid is activated.

- Throttle lock indicator: Informs the operator when the throttle lock is engaged.

- Engine system indicator: Informs the operator of the engine status. Illuminates wheneverthe engine has an active diagnostic.

- Implement system (malfunction) indicator: Illuminates when the implement system hasan active diagnostic or if the optional AccuGrade™ system has an active diagnostic.

- Primary steering system: Illuminates when the primary steering system has an activediagnostic.


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- Action lamp: Illuminates when the machine has a serious issue that requires the operator'sattention. The action lamp will flash whenever there is a level 2 or level 3 event in any ofthe machine systems.

- Parking brake indicator: Illuminates when the parking brake is engaged.

- Transmission system indicator: Illuminates when the Transmission/Chassis ECM has anactive diagnostic or event.

- Secondary steering system indicator: Illuminates when the secondary steering system hasan active diagnostic or event. This indicator will also illuminate when the secondarysteering system is active.

- Differential lock indicator: Illuminates when the differential lock is engaged.

- High beam indicator: Illuminates when the high beams are on.

- Primary brake system indicator: Illuminates when the brake system has an activediagnostic.

- Operator not present indicator: Illuminates when the operator is not present.

NOTE: The operator is considered present if any of the following is true:

- The operator is seated and the Operator in Seat switch recognizes operator as present.- The Transmission Output Speed (TOS) is not zero.- The Actual Gear is not Neutral.- The Inching Pedal is pressed more than 90%.

The operator is considered not present if all of the following are true:

- The Operator in Seat switch does not detect operator presence or the switch is faulted. - The TOS is zero.- The Actual Gear is neutral.- The Inching Pedal is not pressed.

- Right blade float indicator: Illuminates when the right blade control valve is in the floatposition.

- Right turn indicator: Illuminates when the right turn signal is operating.


The left electronic joystick (top illustration) and right electronic joystick (bottom illustration)work in conjunction with the Implement ECMs to give the operator precise control of theimplements. The position sensors and switches in the joysticks provide an input signal to theImplement ECMs. The Implement ECMs will send a corresponding output signal if certainconditions are met.

The electronic functionality of the joysticks will be explained later in this presentation.

Also located to the rear of the right joystick are the horn button (1) and the turn signal switch (2).

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The left joystick controls machine steering. Move the joystick left or right to steer the machine.

Moving the left joystick forward will lower the left side of the blade and moving the leftjoystick to the rear will raise the left side of the blade. Pushing the left joystick all the wayforward (DETENT position) will move the left side of the blade to the FLOAT position.

Rotate the left joystick (1) to the left or right to articulate the machine.

The buttons on the front of the left joystick perform the following functions:

- Wheel lean left (2)

- Wheel lean right (3)

- Transmission upshift (4)

- Transmission downshift (5)

- Articulation recenter (6) - returns the machine articulation to the CENTER (NEUTRAL)position

The transmission direction switch (7) is located on the front of the left joystick.

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Moving the right joystick to the right will allow the blade to sideshift to the right and movingthe right joystick to the left will allow the blade to sideshift to the left.

Moving the right joystick forward will lower the right blade and moving the right joystick tothe rear will raise the right blade. Pushing the right joystick all the way forward (DETENTposition) will move the right side of the blade to the FLOAT position.

Rotate the right joystick to the left or right to rotate the circle drive (1).

The thumb button (2) on the front of the right joystick performs the following functions:

- To move the circle to the left push the left side of the thumb button.

- To move the circle to the right push the right side of the thumb button.

- To pitch the blade forward push the top of the thumb button.

- To pitch the blade to the rear push the bottom of the thumb button.

The trigger switch (3) on the front of the right joystick allows the operator to decelerate orresume engine speed to the previously selected speed. The trigger switch also provides thefollowing functions:

- Holding the trigger switch will decrease engine speed by approximately 100 rpm/sec.

- Tapping the trigger switch will decrease engine speed by 100 rpm increments.

The differential lock switch (4) is also located on the front of the right joystick.

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This illustration shows the joystick decals, which identify the joystick functions.


The ripper control lever (arrow) controls the ripper. This lever is an on/off type input to theImplement 2 ECM. A decal is located below the ripper lever to show the lever function.

Holding the ripper switch down extends the ripper and holding the ripper switch up retracts theripper. When the ripper switch is released, the ripper returns to the HOLD position.

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The "M" Series cab switches are now located on a panel to the right of the operators seat. Thecab switches are as follows:

- Front defroster fan switch (1)

- Rear defroster fan switch (2)

- Parking brake retract switch (3)

- Warning beacon switch (4)

- Heated mirror switch (5)

- Compression brake switch (6)

- Headlight and tail light switch (7)

- Headlight dimmer switch (8)

Also located at the bottom of the panel are the 24V cigar lighter (17), a 12V power port (18),and the Messenger display (19).

- Cab floodlight switch (9)

- Hydraulic lockout switch (10)

- Access light switch (11)

- Front and rear work light switch (12)

- Parking brake switch (13)

- Hazard flasher switch (14)

- Throttle hold mode switch (15)

- Throttle set/accelerate switch (16)

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The "M" series window wiper switches are on the top right of the cab. The switches are:

- Front window wiper (1)

- Rear window wiper (2)

The "M" series heating and air conditioning controls are now located on the top right side of thecab. The controls are as follows:

- Fan speed switch (3)

- Variable temperature control (4)

- Air conditioning on/off switch (5)

An optional radio can be installed below the heating and air conditioning controls.

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The secondary steering test switch (1) and the key start switch (2) are located on the front dash.

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The fuse panel is located at the right rear of the cab. The fuse panel contains the fuses (1) andrelays (2). A decal (3) is located on the inside of the fuse panel. Circuit breakers located belowthe fuse panel are for the fast speed blower (4) and the condenser fan (5). The CaterpillarElectronic Technician (Cat ET) connector (6) is also located below the fuse panel.

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These illustrations show some additional cab components.

The service brake pedal (1), the accelerator pedal (2) are located on the floor of the cab.

The variable float switch (4) activates the variable float feature. The left variable float dial (5)controls the amount of lift force or float force that is applied to the working surface by the leftside of the blade. The right variable float dial (6) controls the amount of lift force or float forcethat is applied to the working surface by the right side of the blade.

The cab air filter is accessed by removing the air filter cover (7) located at the rear of the cab.

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The air suspension seat has an air bag that controls the height of the seat and the weightadjustment of the seat. The amount of air in the air bag is determined by the operator. Thepressure in the air bag is determined by the weight of the operator. Damping is provided by theshock absorber (1).

The seat also includes the following controls:

- Backrest adjustment lever (2)

- Height adjustment knob (3)

- Fore/aft lever (4)

- Wrist rest height adjustment knob (5)

- Control pod fore/aft lever (6)

- Arm pad adjustment knob (7)

- Control pod vertical adjustment knob (8)


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MESSENGER

Messenger Main Menu

The menu structure for Messenger is arranged in a stair step, or hierarchical list format. Whenthe operator, or technician, selects an option from a menu, the resulting screen is one leveldown from that selection. More selections, or options, may be available from that screen, aswell. There may be more than one page of information, or options, to be displayed from anylevel. These levels can be accessed by using the left, right, up, or down arrows as necessarydepending on how the data or list is arranged.

The following options are available from the Messenger's Main Menu screen:

- Performance

- Totals

- Settings

- Service


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Performance Menu Options

The Performance Menu options are as follows:

- Engine Speed: This option will show the engine rpm.

- Ground Speed: This option will show the ground speed in Miles per Hour or in Kilometers per Hour.

- Engine Coolant Temp: This option will show the engine coolant temperature in degrees Fahrenheit or in degrees Celsius.

- Articulation Angle: This option will displays the articulation angle.

- Fuel Level: This option will show the amount of fuel that is measured in the fuel tank as a percentage of a full tank.


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- Hydraulic Oil Temp: This option will show the hydraulic oil temp in degrees Fahrenheit or in degrees Celsius.

- Required Gear: This option will show the gear that the operator desires.

- Actual Gear: This option will show the gear that is currently engaged inthe transmission.

- TOS: This option will show the transmission output speed in rpm.

- Trans Oil Temp: This option will show the transmission oil temp in degreesFahrenheit or in degrees Celsius.

- Implement Lock Out: This option will show status of the implement lockout switch.

- Pilot supply: This option will show the status of the pilot supply solenoid, which is turned ON or OFF by the implement lockout switch.

- Blade L. Lift Cyl: This option will show if the left blade lift cylinder is in float or not in float.

- Blade R. Lift Cyl: This option will show if the right blade lift cylinder is in float or not in float.

- Sec Steer Test: This option will show if the Secondary steering test is active or inactive.

- Sec Steer Signal: This option will show if the implement ECM is requesting a secondary steering function from the transmission/chassis ECM.

- Charge Filter: This option will show if the charge filter is filtering or bypassing oil.


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Totals Menu Options

Lifetime Totals

Use the scroll up/left button and the scroll down/right button to move between the variousscreens and use the "Back" button to return to the "Totals" Menu.

NOTE: These totals cannot be zeroed without a factory password.

- Forward: This option displays the distance that the machine has driven in forward gear during the machine's lifetime.

- Reverse: This option displays the distance that the machine has driven in reverse gear during the machine's lifetime.

- Total Fuel: This option displays the information about the fuel consumption of the machine during the machine's lifetime.

- Service Hours: This option displays the number of hours that the machine has been operating during the machine's lifetime.


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Trip Totals


Individual trip totals can be reset in the Trip Reset menu.

- Total Fuel: This option displays the information about the fuel consumption of the machine during a trip or shift.

- Service Hours: This option displays the number of hours that the machine has been operating during a trip or shift.

Trip Reset


- Clear Trip Totals: Clear all trip totals or Return to previous screen.


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Settings Menu Options

Monitoring System

- Language: Select this option to change the language that is shown onthe display. Currently only English is available. In thefuture, the choices will be English, Spanish, and French.

- Units: Select this option to choose either the US or the Metricmeasurement system.

- Contrast: Select this option to adjust the contrast of the display. Thiswill improve the visibility of the information. The displayprovides a bar graph for viewing adjustments.

- Backlight Select this option to adjust the backlighting of the display.This will improve the visibility of the information. Thedisplay provides a bar graph for viewing adjustments.


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Machine

- Product ID: Displays the machine serial number.

- Equipment ID: Displays the equipment identification number.

Transmission

- Initial Fwd Gear: Allows the operator to view and change initial gear used toshift out of neutral while in manual mode.

- Initial Rev Gear: Allows the operator to view and change initial gear used toshift out of neutral while in manual mode.

- Min Fwd Autoshift Gear: Allows the operator to view and change minimum gearused for auto shift.

- Min Rev Autoshift Gear: Allows the operator to view and change minimum gearused for auto shift.

- Max Fwd Autoshift Gear: Allows the operator to view and change maximum gearused for auto shift.

- Max Rev Autoshift Gear: Allows the operator to view and change maximum gearused for auto shift.

- Transmission Oil Type: Allows the operator to view the oil viscosity.

Autolube

- Interval: Allows the operator to view and change the autolubeinterval.

- Duration: Allows the operator to view and change the autolubeduration.


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Service Menu Options

- Diagnostics/Events: Select this option to view events that are logged by themonitoring system.

System Parameters

Use the scroll up/left button and the scroll down/right button to move between the variousscreens and use the "Back" button to return to the Service Menu.

Monitoring System

- Battery Voltage: This option displays battery voltage.

- Fuel Level: This option displays amount of fuel that is measured in thefuel tank as a percentage of a full tank.

- Alternator Status: This option displays the status of the alternator (checkwhen running).


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Engine

- Engine Speed: This option displays the engine.

- Desired Engine Speed: This option displays the desired engine speed.

- Oil Pressure: This option displays the engine oil pressure.

- Engine Coolant Temp: This option displays the engine coolant temperature.

- Fuel Temp: This option displays the fuel temperature.

- Fuel Pressure: This option displays the fuel pressure.

- Air Temp: This option displays the intake air temperature.

- Atmospheric Pressure: This option displays the atmospheric pressure.

- Right Turbo Inlet Pressure: This option displays the turbo inlet air pressure.

- Turbo Outlet Pressure: This option displays the turbo outlet pressure.

- Boost Pressure: This option displays the boost pressure.

- Fuel Position: This option displays the fuel position.

- Throttle Position Sensor: This option displays the throttle position in a percentage.

Transmission

- Req. Gear: This option displays the gear the operator is requesting.

- Actual Gear: This option displays the gear the machine is in.

- TOS (Trans output speed): This option displays the transmission output speed.

- Tran Oil Temp: This option displays the temperature of the transmissionoil.

- Trans Charge Filter: This option displays if the transmission filter is bypassingor filtering.


Steering

- Steering Control Pos: This option displays the percentage of travel of thesteering function on the left joystick.

- Steer Duty Cycle: This option displays duty cycle, in percentage, of thesteering lever sensors.

- Left Cyl Ext: This option displays the percentage of travel of the leftsteering cylinder.

- Right Cyl Ext: This option displays the percentage of travel of the rightsteering cylinder.

- Sec Steer Pos: This option displays the position of the secondary steeringswitch located on the dash.

- Sec Steer Test: This option displays whether or not the operator hasrequested a secondary steering test.

- Sec Steer Signal: This option displays whether or not the Implement ECM isrequesting a secondary steering function from theTransmission/Chassis ECM.

Implement

- Hydraulic Oil Temp: This option displays the temperature of the hydraulic oil.

- Hydraulic Oil Pressure: This option displays the pressure of the oil at the outlet ofthe implement and steering pump.

- Implement Lockout: This option displays the status of the implement lockoutswitch.

- Pilot Status: This option displays whether or not the implement pilotsolenoid is energized or not.

- Blade Left Lift Pos: This option displays the percentage of travel of the leftblade cylinder function on the left joystick.

- Blade Left Lift Cyl: This option displays whether or not the left blade cylinderis in float.


- Blade Right Lift Pos: This option displays the percentage of travel of the rightblade cylinder function on the right joystick.

- Blade Right Lift Cyl: This option displays whether or not the right bladecylinder is in float.

- Wheel Left Lean Pos: This option displays the percentage of travel of the leftwheel lean function on the left joystick.

- Wheel Right Lean Pos: This option displays the percentage of travel of the rightwheel lean function on the left joystick.

- Pitch Forward: This option displays the percentage of travel of the bladepitch forward function on the right joystick.

- Pitch Backward: This option displays the percentage of travel of the bladepitch backward function on the right joystick.

- Side Shift Pos: This option displays the percentage of travel of the sideshift function on the right joystick.

- Circle Left Side Shift: This option displays the percentage of travel of the circleside shift left function on the right joystick.

- Circle Right Side Shift: This option displays the percentage of travel of the circleside shift right function on the right joystick.

- Circle Drive Pos: This option displays the percentage of travel of circle drivefunction on the right joystick.

- Articulation Pos: This option displays the percentage of travel of thearticulate function on the left joystick.

- Auto Articulation Pos: This option displays the position that the auto articulationrecenter switch is in.


Brake

- Brake Switch (Parking): This option displays the position of the parking brakeswitch on the dash.

- Brake Solenoid: This option displays whether or not the parking brakesolenoid is energized.

- Park Brake Pressure: This option displays the pressure of the parking brakesystem.

- Park Brake: This option displays the status of the parking brakesystem.

- Service Brake Pedal: This option displays if the service brake pedal is depressedor released.

System Test

System Self-Test

- 3 Sec Self-Test: This option will cause the instrument cluster to do a powerup test that will turn on all indicators and sweep thegauges.

System Information

Engine

- System Information: Engine Serial Number, ECM Serial Number, ECM PartNumber, Software Group Part Number, Software GroupRelease Date, Software Group Description.

Trans/Chassis

- System Information: ECM Serial Number, ECM Part Number, Software GroupPart Number, Software Group Release Date, SoftwareGroup Description.

Monitoring System

- System Information: Equipment ID, ECM Serial Number, ECM Part Number,Software Group Part Number, Software Group ReleaseDate, Software Group Description.


Implement System


Implement 2 System


Service Test

- Manual Lube Mode: Activates the Auto Lube system.

Tattletale

Tattletale Mode Active: Upon activating Tattletale Mode, all gauges will sweep totheir maximum or minimum recorded position. Once inTattletale Mode, individual maximum/minimumparameters can be viewed in numerically expressedmeasurements on the Messenger display, or viewed as agauge reading on the Instrument Cluster.

- Oil Temp: Displays maximum recorded oil temperature.

- Coolant Temp: Displays maximum recorded coolant temperature.

- Engine Speed: Displays maximum recorded engine speed.

- Articulation Angle: Displays direction and angle of farthest articulation.

- Fuel Level: Displays minimum recorded fuel level.


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ECM ARCHITECTURE

The "M" series motor graders are equipped with five standard ECMs and can have additionalECMs depending on machine configuration. The standard ECMs are as follows:

- Engine ECM (A4 E4)

- Implement ECM (A4 M1)

- Implement 2 ECM (A4 M1)

- Transmission/Chassis Control (A4 M1)

- Messenger


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Communication between the ECMs is conducted over data link circuits. The data link circuitsare bidirectional, allowing the ECMs to send and receive information. The ECMs support twotypes of data link systems:

- Cat Data Link (CDL): The Cat Data Link is used to send system status informationbetween ECMs and Cat ET.

- SAE J1939 (CAN): The SAE J1939 Data Link is used for high speed system operationand communication between the ECM controls and the ECMs of other machine systems.

NOTE: In the event of a failure of the SAE J1939 Data Link system, the Cat Data Linkis used as a back-up system for operational communication.

Several of the machine ECMs have the same part number. Each of these ECMs with the samepart number is assigned a location code. This location code tells the ECM what function it willperform. The location code is determined by the grounding of pins 26, 27, 28, or anycombination on J1. The machine ECMs can be flashed with a file that is not correct for thelocation code (example: An Implement 3 flash file can be downloaded to aTransmission/Chassis ECM). If a flash file does not match the location code, a 1326-02diagnostic code will be activated.


ECM P/N Location Code ECM Suffix

Engine 262-2878 N/A JL

Implement 262-1408 2 JT

Implement 2 262-1408 3 JT

Messenger 239-5025 N/A HL

Product Link 239-9954 N/A LQ

Transmission 262-1408 1 JT

24

C18 ACERT™ ENGINE

The C18 ACERT™ engine utilizes the A4 Electronic Control Module (ECM) engine controland is equipped with an Air to Air Aftercooler (ATAAC) intake air cooling system.

The Engine ECM utilizes the ADEM IV to control the fuel injector solenoid and to monitor fuelinjection. The fuel is delivered through a Mechanical Electric Unit Injection (MEUI) system.ACERT™ Technology provides an advanced electronic control, a precision fuel delivery, andrefined air management.

The C18 engine is an in-line six-cylinder arrangement with a displacement of 18.1 L.

The C18 ACERT™ engine meets all US Environmental Protection Agency (EPA) Tier IIIEmission Regulations for North America and Stage IIIa European Emission Regulations.


25

Engine Electronic Control System Block Diagram

This block diagram of the engine electrical system shows the components that are mounted onthe engine. The components provide input signals and receive output signals from the EngineElectronic Control Module (ECM).

Based on input signals, the Engine ECM energizes the injector solenoid valves to control fueldelivery to the engine and energizes the cooling fan solenoid valve to adjust fan speed.

The two interface connectors provide electrical connections from the engine to the machineincluding the CAN Data Link and the Cat Data Link.

Some of the components connected to the Engine ECM through the connectors are: throttlepedal position sensor, throttle mode switch, and the ground level shutdown switch.


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Input Components:

Camshaft speed timing sensor - The speed timing sensor sends a fixed voltage level signal tothe Engine ECM in order to determine the engine speed, direction, and timing.

Crankshaft speed timing sensor - The speed timing sensor sends a fixed voltage level signalto the Engine ECM in order to determine the engine speed, direction, and timing.

Atmospheric pressure sensor - This sensor is an input to the Engine ECM and is used as areference for air filter restriction. Also, the sensor is used to supply information to the EngineECM during operation at high altitude.

Turbo inlet pressure sensor - This sensor is an input to the Engine ECM to supplyinformation about the air restriction before the turbocharger. The ECM uses this informationfor engine derates and logged events.

Intake manifold air temperature sensor - This sensor supplies air temperature data at theintake manifold to the Engine ECM. The ECM uses this information for engine derates andlogged events.

Fuel differential pressure switch - This switch relays information to the ECM that the fuelpressure at the output of the filter base is restricted in comparison to the inlet pressure.

Coolant temperature sensor - This sensor is an input to the Engine ECM supplyinginformation on the temperature of the engine coolant. The ECM uses this information for fansolenoid current, high coolant temperature warnings, engine derates for high coolanttemperature, or logged events.

Fuel temperature sensor - This sensor sends fuel temperature data to the Engine ECM. TheECM uses this information for engine derates and logged events.

Engine oil pressure sensor - This sensor is an input to the Engine ECM to supply aninformation warning for low oil pressure, engine derates for low oil pressure, or logged events.

Throttle pedal position sensor - This sensor sends the throttle position to the Engine ECM inorder to increase or decrease the fuel supply to the injectors.

Key switch ON (+B) - The Key ON input to the Engine ECM enables the ECM for operationand is recognized by any ECM on the machine.

Ground level shutdown switch - This switch is an input to the Engine ECM. This inputdisables fuel injection when the engine is running or at engine start-up.

Intake manifold air pressure sensor - This sensor is an input to the Engine ECM to supplyinformation about the air pressure into the intake manifold.


Throttle mode switch - The switch relays information to the ECM for manual and automaticthrottle controls.

Throttle resume/decel switch - The switch relays information to the ECM to decel or resumeengine rpm.

Throttle set/accel switch - The switch relays information to the ECM to set or accelerateengine rpm.

Timing calibration connector - Connector used for timing the engine with Cat ET.

Output Components:

+5 Volt - Regulated supply voltage for the sensor inputs to the Engine ECM.

+8 Volt - Regulated supply voltage for the sensor inputs to the Engine ECM.

Fan solenoid valve - Proportional solenoid valve that controls the signal pressure to the brakeand hydraulic fan pump in order to meet the varying cooling requirements of the machine.

Ether aid solenoid - On/off solenoid valve that injects ether to start the engine in cold weather.

Fuel pump relay - Relay used to turn the electric fuel pump on when the key start switch isturned to the ON position.

Fuel injectors - Proportional solenoids that control the fuel to the combustion chamber.

Engine brake solenoids - On/off solenoids that control engine oil to the compression brakepistons.


26

Fuel System Block Diagram

Fuel is drawn from the fuel tank through the primary fuel filter and water separator by a gear-type fuel transfer pump. The fuel transfer pump then directs the fuel through the secondary fuelfilter.

The fuel then flows to the cylinder head. The fuel enters the cylinder head and flows into thefuel gallery, where it is made available to each of the six MEUI fuel injectors. Any excess fuelnot injected leaves the cylinder head and flows back to the secondary fuel filter. Then, theexcess fuel flows past the fuel pressure regulator.

The fuel pressure regulator is a check valve that is installed in the secondary fuel filter. Thefuel pressure regulator maintains fuel system pressure between the fuel transfer pump and thefuel pressure regulator.

From the fuel pressure regulator, the excess fuel flow returns to the fuel tank. The ratio of fuelused for combustion and fuel returned to tank is approximately 3:1 (i.e. four times the volumerequired for combustion is supplied to the system for combustion and injector coolingpurposes).


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A differential pressure switch is installed in the secondary fuel filter base and will alert theoperator of a fuel filter restriction. The differential pressure switch compares the filter inletpressure to the filter outlet pressure. When the difference in the inlet and outlet pressurescauses the switch to activate, the Engine ECM will signal Messenger to warn the operator thefuel flow is probably restricted.

A fuel pressure sensor is installed in the secondary fuel filter base and will signal the EngineECM of a high fuel pressure. If the fuel pressure exceeds a pressure of 758 kPa (110 psi) theEngine ECM will log a E096 code.

In the case of a logged high fuel pressure Event, check the following Fuel System'sComponents:

- Inspect the fuel transfer pump pressure relief valve that is in the body of fuel transferpump. Check for damage to the spring or to the valve assembly.

- Verify that the pressure regulating valve in the fuel filter manifold is operating correctly.Check for damage or for dirt in the valve assembly.

- Check the return line from the fuel filter base to the fuel tank for damage or collapse.


27

Engine Component Locations

The Engine ECM (1) is located on the left side of the engine. The Engine ECM has a 70-pinconnector (2) and a 120-pin connector (3). The connectors are identified as "J1" and "J2." Besure to identify which connector is the J1 or J2 connector before performing diagnostic tests.

Occasionally, Caterpillar will make changes to the internal software that controls theperformance of the engine. These changes can be performed by using the WinFlash programthat is part of the laptop software program Cat ET. Cat ET is used to diagnose and program theelectronic controls used in Caterpillar products. If using the WinFlash program, a "flash" filemust be obtained from Caterpillar and uploaded to the ECM.


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28

The crankshaft speed/timing sensor (1) is located on the lower right side of the timing gearcover. The crankshaft sensor is the primary speed sensor reporting to the Engine ECM with theengine speed and position of the crankshaft. The crankshaft speed/timing sensor sends afrequency signal to the Engine ECM on contact J2-35 and contact J2-25 indicating crankshaftspeed. The speed/timing sensors serve four functions in the engine electronic control system:

1. Engine speed measurement

2. Engine timing measurement

3. TDC location and cylinder number identification

4. Reverse rotation protection

If the signal from the crankshaft speed timing sensor is lost or intermittent, normally a CID0190 FMI 08 Engine Speed Abnormal will be logged and can be viewed through Cat ET.

NOTE: If the engine is running and the signal from the crankshaft is lost, a slightchange in performance is noticed during change over to the camshaft sensor.


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The camshaft speed/timing sensor (2) is located on the rear of the engine timing gear housingnear the intake manifold pressure sensor (3). Under normal operation, the camshaftspeed/timing sensor determines the No. 1 compression timing prior to the engine starting. Ifthe camshaft sensor is lost, a CID 342 MID 08 Secondary engine speed signals an abnormalcode is active and the crankshaft sensor will time the engine with an extended starting time.The engine will run rough until the Engine ECM determines the proper firing order using thecrankshaft sensor only. In the case that the signal from both engine speed sensors is lost, theengine will not start. During a running condition, the engine will shutdown.

The sensor serves as a back-up for the crankshaft speed/timing sensor. If the crankshaftspeed/timing sensor fails, the camshaft speed/timing sensor allows for continuous operation.

The fuel transfer pump (4) is a gear pump that is located near the balancer at the front of theengine. The fuel transfer pump is driven by the front gear train. Fuel is drawn from theprimary fuel filter and water separator by the fuel transfer pump and is directed to thesecondary fuel filter.

The fuel transfer pump incorporates a check valve. The check valve allows fuel to flow aroundthe gears of the pump when the fuel system is primed. A relief valve (not shown) is alsoinstalled in the fuel transfer pump. The relief valve limits the maximum fuel pressure in thefuel system.


29

The atmospheric pressure sensor (1) is located on the left side of the machine on the engine.The Engine ECM uses the sensor as a reference for air filter restriction and derating the engineunder certain parameters. All pressure sensors in the system measure absolute pressure and,therefore, require the atmospheric pressure sensor to calculate gauge pressures.

The atmospheric pressure sensor is one of the many sensors that require a regulated 5.0 VDCfor the sensor supply voltage. The atmospheric pressure sensor outputs a variable DC voltagesignal.

If the engine requires timing calibration, a timing sensor (magnetic pickup) is installed in theengine block at location (2) and connected to the timing calibration connector (3) located abovethe Engine ECM.

Using the Cat ET service tool, the timing calibration is performed automatically. The desiredengine speed is set to 800 rpm. This step is performed to avoid instability and ensures that nobacklash is present in the timing gears during the calibration process.

Timing calibration improves fuel injection accuracy by correcting for any slight tolerancesbetween the crankshaft, timing gears, and timing wheel.


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Timing calibration is normally performed after the following procedures:

- ECM replacement

- Engine overhaul

- Active code that requires a timing calibration


The primary fuel filter (1) is mounted near the left rear side of the engine. The primary filtercontains a water separator which removes water from the fuel. Water in a high pressure fuelsystem can cause premature failure of the injector due to corrosion and lack of lubrication.Water should be drained from the water separator daily, using the drain valve that is located atthe bottom of the filter.

The primary filter has an electric fuel priming pump integrated into the filter base. The primingpump is activated automatically by the Engine ECM. The Engine ECM sends a signal to thefuel pump relay located behind a cover (2) which energizes the fuel priming pump. Theelectric fuel priming pump (3) is used to fill the fuel filters with fuel after they have beenreplaced.

30

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The relay for the electric fuel priming pump is energized for 120 seconds when one of thefollowing conditions occur:

- Key start switch is turned to the ON position (engine not running)

- When the engine is cranking

- After the engine has been shutdown

The fuel system is also equipped with a high efficiency secondary fuel filter (4). This filter islocated on the left side of the engine. The fuel regulator (not shown) is integrated into thesecondary fuel filter base. The fuel pressure regulator regulates the the flow of fuel from thefuel gallery.


32

The engine coolant temperature sensor (1) is located on the front of the engine, on the watertemperature regulator housing (2). The input to the Engine ECM from this sensor provides thefollowing temperature information:

- The Instrument Cluster coolant temperature gauge and the high coolant temperaturewarning alert indicator LED on the Caterpillar Instrument Cluster.

- The temperature input for the ether aid system operation.

- The Caterpillar Electronic Technician (Cat ET) status screen coolant temperatureindication.

NOTE: If the coolant temperature exceeds 110° C (230° F) an event is logged in theEngine ECM. Also, the ECM will automatically derate the fuel delivery to protect theengine.

Also visible in this illustration is the coolant S•O•S tap (3).


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The coolant temperature sensor measures the temperature of the coolant.

When the temperature of the coolant exceeds 110° C (230° F), the Engine ECM will initiate aLevel 1 Warning.

When the temperature of the coolant exceeds 111° C (231° F), the Engine ECM will initiate aLevel 2 Warning. At 111° C (231° F) the Engine ECM will initiate a 25% derate. Refer to theillustration for the remainder of the high engine coolant temperature derates. At 100% derate,the engine available power will be approximately 50%.


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The engine oil pressure sensor (1) is located on the left side of the engine near the Engine ECM (2). The sensor monitors the pressure of the engine oil.

The sensor receives a +5 VDC signal from the Engine ECM on contact J2-72 and sends an oilpressure signal to the ECM on contact J2-28.

The Engine ECM will use the information supplied by the oil pressure sensor to output warninglevels to Messenger and derate the engine.


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This illustration shows a graph with the two different warning levels for low oil pressure.

When the oil pressure is below the blue line (154 kPa @ 1600 rpm) (22 psi @ 1600 rpm), themonitoring system will enable the low oil pressure Level 1 Warning. Change machineoperation or perform maintenance to the system, in the event of a warning.

When the oil pressure is below the red line (104 kPa @ 1600 rpm)(15 psi @ 1600 rpm), themonitoring system will enable the low oil pressure Level 3 Warning. The operator shouldimmediately perform a safe engine shutdown, in the event of a Level 3 warning.

Also, with the Level 3 Warning, the Engine ECM initiates a 35% engine derate.

If the signal between the Engine ECM and the oil pressure sensor is lost or disabled, the EngineECM will initiate a low engine oil pressure Level 1 Warning.


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The intake manifold pressure sensor/turbocharger outlet pressure sensor (1) is located on theleft side of the engine. The input data from the intake manifold pressure sensor/turbochargeroutlet pressure sensor to the Engine ECM is used by the ECM to electronically control the airfuel ratio. This feature allows very precise smoke control, which was not possible withmechanically governed engines. The intake manifold pressure sensor/turbocharger outletpressure sensor also allows boost pressure to be read using the Cat ET. The intake manifoldpressure sensor/turbocharger outlet pressure sensor receives a +5 VDC signal from the EngineECM on contact J2-72 and sends a signal to the ECM on contact J2-15.

The intake manifold air temperature sensor (2) is also located on the left side of the engine.The air temperature sensor provides air temperature data on contact J2-56 to the Engine ECMto warn the operator of potentially damaging conditions. This sensor is also used for deratingthe engine at high temperature and for use by Messenger.

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The intake manifold air temperature sensor measures the temperature of the air that is flowingto the intake manifold. The sensor is used to initiate warning levels and engine derates.

After the engine is running for at least 3 minutes and if the intake manifold air temperature goesabove 82° C (180° F), the Engine ECM will initiate a Level 1 Warning.

After the engine is running for at least 3 minutes and if the intake manifold air temperature goesabove 86° C (187° F), the Engine ECM will initiate a Level 2 Warning. With the Level 2Warning, the Engine ECM signals the engine to initiate a 3% derate. This derate will have a20% upper limit.


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The turbocharger inlet pressure sensor (arrow) is located in a tube between the air cleaners andthe turbocharger. The Engine ECM uses the turbocharger inlet pressure sensor in combinationwith the atmospheric pressure sensor to determine air filter restriction. The Engine ECMprovides the input signal to the monitor system, which informs the operator of the air filterrestriction.

The sensor receives a +5 VDC signal from the Engine ECM on contact J1-2 and sends a signalto the ECM on contact J1-15.


40

The turbo inlet pressure sensor measures the restriction of the air inlet that is flowing to theinlet of the compressor housing of the turbocharger. When the pressure difference between theturbo inlet pressure sensor and the atmospheric sensor read a difference of 9.0 kPa, the EngineECM will derate the engine approximately 2%. The Engine ECM will then derate the engine2% more for every 1 kPa difference up to 10%.

Typically the atmospheric pressure sensor is 100 kPa at sea level. As the air restrictionincreases, the difference will increase. The first derate will occur when the difference isapproximately (100 kPa minus 91 kPa.= 9 kPa).

If the air inlet restriction is 92.5 kPa (a pressure that is between 7.5 kPa and 9 kPa) for 10seconds, the Engine ECM will initiate a Level 1 Warning.

If the air restriction goes to the point that the turbo inlet pressure sensor sees a difference of91.0 kPa (a pressure that is 9.0 kPa) for 10 seconds, then the Level 2 Warning will occur andthe engine will derate.

NOTE: This air inlet restriction derate is a latching derate. The derate will remainactive until the machines is shut down.


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The differential fuel pressure switch (1) is located in the top of the secondary fuel filter housingon the left side of the engine. This switch indicates restriction in the fuel filter and provides aninput to the Engine ECM. A warning is also sent by the Engine ECM to Messenger.

The fuel pressure sensor (2) is located in the top of the secondary fuel filter housing on the leftside of the engine. This sensor is used to monitor fuel pressure and receives a +5 VDC signalfrom the Engine ECM and sends a signal to the ECM indicating fuel pressure.

The fuel temperature sensor (3) provides an input to the Engine ECM. The Engine ECM usesthe fuel temperature measurement data from the fuel temperature sensor to make corrections tothe fuel rate to maintain power regardless of fuel temperature (within certain parameters). Thiscorrection feature is called "Fuel Temperature Compensation."

41


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This illustration shows the graph for the warning and the derates map for the fuel temperature.When the fuel temperature exceeds 90° C (194° F), the Engine ECM will activate a Level 1Warning. When the fuel temperature increases to 91.0° (196° F) a Level 2 Warning will beinitiated by the Engine ECM. At the same time, the engine will derate to 12.5%. If the fueltemperature exceeds 92° C (198° F), the engine will be derated to 25%.

A fuel temperature sensor open circuit will derate the engine to 12.5%.


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When the differential pressure switch recognizes a fuel pressure of 103 kPa (15 psi) for 3minutes, the Engine ECM will initiate a Level 1 Warning.

When the differential pressure switch recognizes 103 kPa (15 psi) across the filter for 4 hours,the Engine ECM will initiate a Level 2 Warning. With the Level 2 Warning initiated, a 17.5 %derate is applied to the engine. After 1 second, the Engine ECM will initiate a second derate of17.5%. The total derate will be 35%.

NOTE: This feature will be disabled when the fuel temperature is below 30° C (86° F).


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An engine derate can occur due to a estimated (virtual) high exhaust gas temperature. TheEngine ECM monitors barometric pressure, intake manifold temperature, and engine speed toestimate exhaust gas temperature. Certain conditions (high altitude, high ambient temperatures,high load and full accelerator pedal throttle, barometric pressure, intake manifold temperature,and engine speed) are monitored to determine if the engine derate should be enabled. TheEngine ECM determines a maximum fuel delivery percentage to maintain safe maximum poweroutput under load. This calculation is new to the off-road Tier III engines and is used in placeof the previous altitude compensation derate strategy.

This event is to inform the mechanic that a derate has occurred because of operating conditions.Generally, this is normal and requires no service action.

The Engine ECM will process all derate inputs in the highest derate priority selector. The mostcritical derate condition input will be used to adjust fuel system delivery limiting engine powerto a safe level for the conditions in which the product is being operated, thereby preventingelevated exhaust temperatures.


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The virtual exhaust temperature derate will log a 194 event code. The derate will enable aLevel 1 Warning and eventually a Level 2 Warning. The level of the warning will depend onthe conditions that are sent to the Engine ECM.

The following conditions must be met to initiate a virtual exhaust temperature derate.

- No CID 168 01 FMI (low battery voltage to the Engine ECM) are active.

- No active intake manifold pressure sensor faults.

- No active atmospheric pressure (barometric) sensor faults.

- No +5 V sensor voltage codes active.

- The virtual exhaust temperature derate must be the highest derate.

- More fuel is being requested than the virtual exhaust temperature derate will allow.

This derate is triggered by the information inferred by the Engine ECM, rather than anindividual sensor as with the previous single derate strategies. If you think this derate ispossibly being imposed incorrectly, check for event codes on high intake manifold temperature.Correct any codes first. Also, make sure the aftercooler is unobstructed. For additionalinformation about troubleshooting, refer to the troubleshooting guide for the particular enginethat is being serviced.


The ether start control has changed with the introduction of the Tier III machines. The ethersystem (if equipped) is now automatically controlled by the Engine ECM. Ether control alsonow utilizes one continuous shot instead of a one shot application.

The Engine ECM energizes the ether solenoid (arrow) for a predetermined amount of time thatis based on ECM software. The ECM monitors the coolant temperature sensor, air temperaturesensor, and the atmospheric pressure sensor to determine the temperature and altitude of themachine. Based on these inputs, the ECM will determine if ether is required.

The ether injection system can be enabled or disabled using Cat ET.

45


The radiator (1) and air to air aftercooler (2) now sit side by side in the cooling package. TheC18 is equipped with a wastegate turbocharger which provides higher boost over a wide range,improving engine response and peak torque, as well as outstanding low-end performance.

NOTE: The wastegate is preset at the factory.

Also located in this illustration is the brake and hydraulic fan oil cooler (3).

46


12

3

Throttle mode switch (1) allows the operator to select between two different throttle modes:

- Automatic Mode: When the top of the throttle hold mode switch (1) is depressed, thethrottle mode is set to automatic. In automatic mode, the operator can set the engine rpmwith the throttle pedal (not shown) or with the set/accelerate switch (2). If the operatorwants to decrease the engine rpm, the operator can depress or depress and hold theresume/decelerate switch (3) to decrease engine rpm. If the brake pedal is depressed atany time when the automatic mode has been selected, the engine will return to low idle.If resume/decelerate is depressed, the engine rpm will return to the previous set point.

47

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- Manual Mode: When the bottom of the throttle hold mode is depressed, the throttlemode is set to manual mode. The operator can set or decrease the engine rpm in the sameway as automatic mode. The brake pedal does not decrease the engine rpm to low idle.To return the engine to low idle, the throttle hold mode switch should be placed in theOFF position (center).


The throttle position sensor (arrow) sends a PWM signal to the Engine ECM indicating thethrottle pedal position.

49


The ground level shutdown switch (arrow) sends a signal to the Engine ECM to shut down theengine.

50


The fan solenoid (arrow) receives a signal from the Engine ECM, which controls the fan speed.

51


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Engine Idle Management

Cool Engine Mode - In cold weather operation, the engine rpm will be set to 1000 rpm inorder to generate additional engine heat, keeping the engine warmer. This mode monitors thecoolant temperature and the intake manifold temperature. When the coolant temperature isbelow 80° C (176° F) or the intake manifold temperature is below 15° C (60° F) and the coolengine mode is enabled, the machine will time out for 10 minutes. After ten minutes, if thecoolant temperature is below 70° C (158° F) and the machine has been in the cool engine mode,the engine will be in the cool engine mode. If the machine has not been in cool engine modebut the intake manifold temperature is less than 5° C (41° F), the engine will go into the coolengine mode.

Low Voltage Mode - In this mode, the engine will ramp up to 1000 rpm when the batteryvoltage drops below 24.5 volts for more than five minutes. When the battery voltage is greaterthan 24.5 volts, the engine idle will return to low idle.

NOTE: The Engine Idle Management Strategies can not be reconfigured with Cat ET.

52


Engine Brake

The C18 ACERT™ is equipped with an engine compression brake (arrow). The machine usesvalve timing change to open the exhaust valves before TDC during the compression stroke toproduce negative engine torque. The value to the machine from using the compression brake isreduced engine overspeeds, reduced brake oil temperatures, and extended brake component life.

When the operator moves the engine brake selector switch in the cab to the AUTOMATICposition a signal is sent to the Transmission/Chassis ECM. The Transmission/Chassis ECMcommunicates with the Engine ECM over the CAT Data Link.

The Engine ECM activates the engine brake when the following conditions are met:

- Transmission/Chassis ECM communicates to the Engine ECM the required retardinglevel.

- The engine speed is above 1000 rpm

- The desired engine speed is at low idle.

The engine brake will be deactivated when the engine speed is below 950 rpm and reactivatedif the engine speed rises above 1000 rpm.

53


The following cylinders are enabled when the selector switch is in the activated position.

Low (3 and 4)

Medium (1 and 2) (5 and 6)

High (1 and 2) (3 and 4) (5 and 6)

The ECM will disable injection to that cylinder while the engine brake is active.


54

This illustration shows the basic principle of engine compression brake retarding.

During normal engine operation without the engine brake enabled, the following actions occur:

1. Intake stroke: The intake valve opens and air is forced into the cylinder by boostpressure from the turbocharger.

2. Compression stroke: Air is compressed by the engine piston. The energy required tocompress this air is produced by the vehicle's driving wheels.

3. Power stroke: When the piston passes over top dead center and begins the powerstroke, the energy is returned to the piston (and to the driving wheels). Essentially noenergy is absorbed and no net retarding work is done.

4. Exhaust stroke: Air is forced out through the exhaust.


When the engine compression brake is activated, the following actions occur:

1. Intake stroke: The intake valve opens and air is forced into the cylinder by boostpressure from the turbocharger.

2. Compression stroke: Air is compressed to approximately 3450 kPa (500 psi) by theengine piston. The energy required to compress this air is produced by the vehicle'sdriving wheels. Near top dead center, the compression brake opens the exhaust valve,venting the high pressure air and dissipating the stored energy through the exhaustsystem.

3. Power stroke: Essentially no energy is returned to the piston (and to the drivingwheels). There is a loss of energy. This loss is how the retarding work is done.

4. Exhaust stroke: Air is forced out through the exhaust.


55

This illustration shows the engine brake disabled. The solenoid valve is de-energized by theEngine ECM. The pump draws oil from the engine sump and sends the oil to the solenoidvalve, where it is blocked. Oil behind the master piston or the slave piston in either cylinderwill flow through the solenoid valve and return to the engine oil sump.


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This illustration shows the engine brake enabled (the lever in the cab will be in either the high,medium, or low position). When the ECM energizes the solenoid valve, the engine oil isdirected past the check valve to the master piston. As the injector rocker moves up, the masterpiston moves up and increases the oil pressure. The increased oil pressure forces the slavepiston down. The slave piston begins to move the rocker arm against the exhaust valves.


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This illustration shows the piston at top dead center. As the slave piston pushes down theexhaust rocker, the exhaust valves open allowing the fuel/air mixture to escape the cylinderthrough the exhaust valves. This will eliminate any compression in the cylinder.

NOTE: When the exhaust valves open, the escaping mixture will give off an audibleresponse.


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This illustration shows the engine with the cam lobe after top dead center. The valve springsforce the exhaust valves closed and with less oil pressure acting on the slave piston, the injectorrocker rotates to the right. The oil pressure in the master cylinder chamber is decreasedallowing the oil in the slave cylinder to direct the oil back into the master cylinder.


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This illustration shows the wiring and components of the engine compression brake. When thecompression brake switch in the cab is activated, the Transmission/Chassis ECM sends a signalto the Engine ECM via the Cat Data Link. The Engine ECM controls the compression brakesolenoids to slow the machine.

The Engine ECM provides three levels of braking: LOW, MEDIUM, and HIGH.

When the ECM commands a LOW braking level, one solenoid will activate the compressionbrake for cylinders 3 and 4.

When the ECM commands a MEDIUM braking level, two solenoids will activate thecompression brake for cylinders 1, 2, 5, and 6.

When the ECM commands a HIGH braking level, all three solenoids will activate thecompression brake for all 6 cylinders.


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60

POWER TRAIN

The 24M power train includes an Electronic Clutch Pressure Control (ECPC) planetarytransmission. The Transmission/Chassis ECM (not shown) controls the modulation of theclutch pressure in the transmission by supplying a variable output current to the appropriateproportional solenoid valve. The Transmission/Chassis ECM monitors the operator gearrequest, engine torque data from the Engine ECM, speed data from the transmission speedsensors, and the transmission temperature to determine the appropriate gear shift. Thetransmission has six forward speeds and three reverse speeds.

The power flow through the power train is as follows:


1

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- Engine (1)

- Torque converter (2)

- Upper drive shaft (3)

- Input transfer gears (4)

- Planetary transmission (5)

- Output transfer gears (6)

- Lower drive shaft (7)

- Differential and final drives (8)

- Chains (9)

- Sprocket (10)

- Wheel stations (11)

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The Transmission/Chassis ECM (1) is mounted on the left side of the transmission (2) on theright side of the machine. The power train electronic control system utilizes a variety ofdifferent types of devices that provide input data to the Transmission/Chassis ECM. TheTransmission/Chassis ECM will use the input data to monitor the machine and also todetermine if an output function is required. Most of the input circuits are monitored fordiagnostics. The Transmission/Chassis ECM will log a diagnostic code if the ECM determinesthat an abnormal condition exists in one of the circuits.

The Transmission/Chassis ECM will also send output signals, which can have a variety ofdifferent functions. The types of electrical output signals are as follows:

- PWM proportional drivers

- On/Off sourcing drivers

- On/Off sinking drivers

- Sensor power supply

- Data link outputs

The Transmission/Chassis ECM also monitors the output circuits for diagnostics.

61


1

2

The Transmission/Chassis ECM has strategies that are used to protect the engine, power train,and machine components, reconfigure certain parameters, and test machine systems. Thestrategies are as follows:

Overspeed protection: This feature ensures that the transmission will never be shifted into agear that would cause an engine overspeed condition by automatically upshifting or notallowing a downshift. The Transmission/Chassis ECM monitors the transmission output speedsensors and the gear that is selected by the operator to determine if it is safe to shift thetransmission.

Limp Home Mode: A limp home mode is available to provide an override to a transmissiondisabling diagnostic event. The limp home mode will be activated by the Transmission/ChassisECM when a diagnostic code is activated for any of the transmission solenoids. TheTransmission/Chassis ECM will allow the transmission to shift to gears that are not affected bythe active diagnostic when the limp home mode is activated.

Low Voltage Shift Inhibit: This feature is designed to prevent excessive transmission clutchwear due to low system voltage by going to neutral whenever a shift is requested and thesystem voltage is low. When the system voltage drops below 20 volts, only shifts to neutralwill be allowed. Any other shift will cause the transmission to shift to neutral. Once thetransmission shifts to neutral due to low voltage, the transmission will remain in neutral untilthe system voltage is at or above 24 volts.

Maximum gear limit: This feature limits the maximum gear that the transmission will shiftinto both in forward and reverse. This feature is set using Cat ET and can be used to limit roadspeed. This feature is not the same as setting a minimum or maximum gear for autoshift.

Park Brake Test: This feature provides a way to test for the correct operation of the parkbrake. The Transmission/Chassis ECM will allow a park brake test to be performed when thetransmission is in 5th gear forward. If the machine drives through the park brake at 5th gearforward in a stall condition, then a problem exists with the park brake.


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Transmission/Chassis Electrical System

Input components:

Operator Present Switch: An input to the ECM that indicates if an operator is in theoperator's seat.

Key Start Switch: Provides a signal to the Transmission/Chassis ECM when the operatorwants to start the engine. The machine conditions must be met before the Transmission/ChassisECM will energize the engine start relay.

Left Hand Joystick: Provides 10 different inputs to the Transmission/Chassis ECM. Some ofthese inputs include: directional control switch, upshift switch, and downshift switch.

Brake Pedal Position Sensor: An input to the ECM to indicate the brake pedal position.

Transmission Filter Bypass Switch: An input to the ECM indicating when the transmissionfilter is in a bypass condition.


Transmission Input Speed Sensor: The sensor that measures the input speed of thetransmission.

Transmission Output Speed Sensors: The sensors measure the transmission output speed.The ECM can determine direction of the transmission by looking at the difference in phasebetween the two sensors.

Torque Converter Oil Temperature Sensor: An input to the ECM that provides thetemperature of the torque converter oil.

Transmission Oil Temperature Sensor: An input to the ECM that provides the temperatureof the power train oil.

Differential Lock Filter Bypass Switch: An input to the ECM indicating when thedifferential lock filter is in a bypass condition.

Parking Brake Switch: An input to the ECM that indicates the operator wants to release theparking brake.

Compression Brake Switch: An input to the ECM to activate the compression brake.

Brake Retraction Switch: An input to the ECM to activate the parking brake retract system.

Parking Brake Pressure Switch: An input to the ECM that provides the status of the pressureto the parking brake.

Lockup Clutch Pressure Sensor: An input to the ECM indicating lockup clutch pressure.

Service Brake Accumulator Pressure Sensor: An input to the ECM that provides thepressure in the service brake accumulators.

Autolube Pressure Sensor: An input to the ECM indicating autolube pressure.

Right Steering Cylinder Position Sensor: Signals the ECM the position of the rod in thesteering cylinder.

Left Steering Cylinder Position Sensor: Signals the ECM the position of the rod in thesteering cylinder.

Articulation Angle Sensor 1 and 2: Signals the ECM the angle of the rear frame as comparedto the angle of the front frame.

Secondary Steering Request Signal: An input from the Implement ECM that that requests theTransmission/Chassis ECM to energize the secondary steering motor relay.


Differential Lock Switch: An input to the ECM that indicates the operator wants to engage ordisengage the differential lock.

Fuel Level Sensor: An input to the ECM indicating the depth of the fuel in the fuel tank.

Air Conditioning Pressure Switch: An input to the ECM that indicates if the air conditioningsystem has a low charge or a high charge condition. Based on the input from the switch, theECM will protect the air conditioning compressor from damage.

+24 Battery Voltage: Unswitched power supplied to the Transmission/Chassis ECM from thebattery.

Location Code 1: The location code pin number 1 is a grounded input signal that establishesthe ECM is dedicated to power train and chassis operations. J1-26 pin on theTransmission/Chassis ECM connector is grounded.

Location Code Enable (GND): The location code enable is a grounded input signal to theTransmission/Chassis ECM that enables the location code enable feature. J1-32 pin on theTransmission/Chassis ECM connector is grounded.

Output Components:

Engine Start Relay: The Transmission/Chassis ECM energizes the engine start relay when theappropriate conditions are met to start the engine.

Autolube Relay: The Transmission/Chassis ECM energizes the autolube relay according tothe input from the Messenger System.

Differential Lock Relay: The Transmission/Chassis ECM energizes the differential lock relaywhen the operator depresses the differential lock switch.

Back-up Alarm Relay: The Transmission/Chassis ECM energizes the back-up alarm relaywhen the operator selects the REVERSE direction.

A/C Clutch Relay: The Transmission/Chassis ECM energizes the A/C clutch relay when airconditioning is requested.

Transmission Clutch Solenoids: The solenoids control the oil flow through the respectivespeed, range, and directional modulating valves.

Parking Brake Solenoid: The Transmission/Chassis ECM energizes the solenoid to releasethe parking brake when all the conditions have been met.


Secondary Steering Solenoids: The Transmission/Chassis ECM sends current to the solenoidsin case of primary steering valve malfunction. The proportional solenoids control the oil flowto the spools in the primary steering control valve.

MSS Status LED: The Transmission/Chassis ECM illuminates the indicator LED with thestatus of MSS.

Autoshift Enabled LED: The Transmission/Chassis ECM illuminates the indicator LED whenautoshift is enabled.

The Transmission/Chassis ECM illuminates the indicator LED when the torque converterlockup clutch is engaged.

+5 Volt Supply: Power supplied to the components from the Transmission/Chassis ECM.




The secondary steering test switch (1) sends a signal to the Implement ECM that the operatorwants to test the operation of the secondary steering valves. When the test switch is depressed,the secondary steering alert indicator in the instrument cluster illuminates amber. If the alertindicator is not illuminated after the test, the test was successful and the steering performancewas normal. If the alert indicator is red the test has failed.

The key start switch (2) sends a signal to the Transmission/Chassis ECM that the operatorwants to start the engine. The Transmission/Chassis ECM determines if the directional controlswitch (on the front of the left joystick) is in the NEUTRAL position and if an operator ispresent. When the directional control switch is in the NEUTRAL position, the operator ispresent, the parking brake switch is in the ON position, and the key start switch is turned to theSTART position, the ECM energizes the starter relay.

63


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The upshift switch (1) and the downshift switch (2) allow the operator to manually upshift ordownshift the gears in the transmission. When the operator commands a downshift that willoverspeed the engine, the Transmission/Chassis ECM will not allow the downshift until it issafe to downshift.

The directional control switch (3) signals the Transmission/Chassis ECM when the operatorwants to shift into forward or reverse. The Transmission/Chassis ECM will not shift intoforward or reverse if the ECM detects a signal from the transmission output speed sensors.

64


The differential lock switch (1) is a momentary switch located on the front of right joystick (2).The differential lock defaults to the unlocked position when the machine is first started.Depressing the differential lock switch sends a signal to the Transmission/Chassis ECM toenergize the differential lock relay. Depressing the lock switch again will send a signal to theECM to de-energize the differential lock relay.

65


1

2

The parking brake switch (arrow) sends a signal to the Transmission/Chassis ECM that theoperator wants to release the parking brake. When an operator is present and the parking brakeswitch has been depressed, the Transmission/Chassis ECM will energize the parking brakesolenoid releasing the parking brake. The steering lever must also be synchronized with thesteering cylinder position sensors before the parking brake can be released.

66


The brake pedal position sensor (not visible) is attached to the brake pedal (arrow). The brakepedal position sensor sends a signal to the Transmission /Chassis ECM indicating brake pedalposition. The ECM uses the brake pedal position signal to illuminate the brake lights and torelease the throttle lock when in automatic mode..

67


The transmission is equipped with three speed sensors that are monitored by theTransmission/Chassis ECM. The ECM uses these sensors to determine both the speed anddirection of the transmission.

The transmission input speed sensor (1) is located at the top of the transmission and providesthe ECM with the transmission input shaft speed. The transmission output speed sensors (2)are located on the top of the output transfer gear on the left side of the machine and provide theECM with the transmission output speed.

68

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The Transmission/Chassis ECM uses these three speed sensors to continually monitor not onlythe speed of the transmission, but also the other speed sensors to determine if they are workingproperly. The ECM can use the transmission input speed sensor to calculate the transmissionoutput speed in the event that both of the transmission output speed sensors fail.


The engine start relay (1) is located on the left side of the engine. The engine start relay iscontrolled by the Transmission/Chassis ECM. When the signal is sent to the ECM to start theengine, the ECM then sends current to the start relay. The coil in the relay closes and batteryvoltage is sent to the starter motor.

The back-up alarm relay, A/C clutch relay, and autolube relay are also controlled by theTransmission/Chassis ECM and are located in the fuse panel (2).

Also shown is the main power relay (3) and the brake retraction relay (4).

70


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The differential lock relay (arrow) is located at the right rear of the cab. The differential lockrelay is energized by the Transmission/Chassis ECM when the differential lock switch isdepressed. When energized, the coil in the relay closes and battery voltage is sent to thedifferential lock solenoid.

71


72

Power Train Hydraulic System

Shown is the transmission and torque converter hydraulic system for the 24M Motor Grader.The transmission pump takes oil from the bottom of the transmission and sends the oil throughthe transmission oil filter, to the torque converter lockup clutch valve, to the main relief valve,and to the transmission control valves.

Oil flows from the torque converter lockup clutch valve to the torque converter lockup clutch.Oil flows from the main relief valve to the torque converter (TC inlet) and torque converterinlet relief valve. Oil from the torque converter then flows to the outlet relief valve and to thetransmission oil cooler.

The main relief valve regulates the torque converter inlet pressure and supply pressure insidethe transmission hydraulic system. Oil unseats the check ball and forces the spool to the right ifthe transmission system pressure becomes greater than the spring force on the right of thespool. Excess oil will flow to the torque converter and to the torque converter inlet relief valve.The main relief valve is adjustable by turning the adjusting screw on the right end of the valve.


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The clutch modulating valves control the engagement of the transmission clutches. Thesolenoids are controlled by a pulse width modulated (PWM) signal from theTransmission/Chassis ECM. Supply oil flows into the clutch modulating valves and through apassage in the center of the spool. Oil then flows to the tank if the solenoid is not energized.Oil flow is blocked by a ball and seat if the solenoid is energized. The spool will shift downand the clutch will begin to fill. The signal from the Transmission/Chassis ECM determineshow long it takes to fill each clutch.


73


This illustration shows the main components in the power train hydraulic system.

The transmission pump (1) is a single section gear pump attached to the pump drive on the leftside of the machine. Oil flows from the pump to the transmission filter (2), to the transmissionmodulating valves and main relief valve (3), and then to the torque converter (4). Some of theoil will leak through the torque converter to the bottom of the housing to be scavenged. Mostof the oil in the torque converter is used to provide a fluid coupling and flows through thetorque converter outlet relief valve (5).

From the outlet relief valve, oil flows to the transmission oil cooler (6). The oil cooler islocated on the left side of the machine.

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The transmission oil filter (1) is located on the left side of the machine next to the hydraulictank.

Oil from the charging pump flows through the transmission oil filter to the transmission and thetorque converter lockup clutch valve.

The filter has a bypass switch (2) which provides an input signal to the monitoring system, viathe Transmission/Chassis ECM, to inform the operator if the filter is restricted. The filterhousing includes an S•O•S tap (3) and a transmission circuit pressure tap (4).

Also visible in this illustration is the case drain oil filter (5).

74


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5

The outlet relief valve (1) maintains the minimum pressure inside the torque converter. Themain function of the outlet relief valve is to keep the torque converter full of oil to preventcavitation. The outlet relief pressure can be measured at the tap location (2) on the outlet reliefvalve.

The torque converter oil temperature sensor (3) sends a signal to the Transmission/ChassisECM indicating torque converter oil temperature.

75


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The torque converter lockup clutch valve (1) directs oil to engage the torque converter lockupclutch. The torque converter lockup clutch pressure can be checked at the tap (2) on top of thelockup clutch valve.

76


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The torque converter lockup clutch modulating valve contains a proportional solenoid thatreceives a signal from the Transmission/Chassis ECM to engage and release the torqueconverter lockup clutch.

In this illustration, the lockup clutch modulating valve is shown with no current signal appliedto the solenoid (TORQUE CONVERTER DRIVE or NEUTRAL). The Transmission/ChassisECM controls the rate of oil flow through the lockup clutch modulating valve to the lockupclutch by changing the signal current strength to the solenoid. With no current signal applied tothe solenoid, the transmission modulating valve is DE-ENERGIZED and oil flow to the clutchis blocked.

Pump oil flows into the valve body around the valve spool and into a drilled passage in thecenter of the valve spool. The oil flows through the drilled passage and orifice to the left sideof the valve spool to a drain orifice. Since there is no force acting on the pin assembly to holdthe ball against the drain orifice, the oil flows through the spool and the drain orifice past theball to the tank.

The spring located on the right side of the spool in this view holds the valve spool to the left.The valve spool opens the passage between the clutch passage and the tank passage and blocksthe passage between the clutch passage and the pump supply port. Oil flow to the clutch isblocked. Oil from the clutch drains to the tank preventing clutch engagement.


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In this illustration, the modulating valve is shown with a maximum current signal commandedto the solenoid. When the modulation cycle stops, the Transmission/Chassis ECM sends themaximum specified current signal to fully engage the lockup clutch (DIRECT DRIVE).

The constant current signal pushes the pin firmly against the ball in the solenoid valve. The pinforce against the ball blocks more oil from flowing through the drain orifice. This restrictioncauses an increase in pressure on the left side of the valve spool. The valve spool moves to theright to allow pump flow to fully engage the clutch.

In a short period of time, maximum pressure is felt at both ends of the proportional solenoidvalve spool. This pressure along with the spring force on the right end of the spool cause thevalve spool to move to the left until the forces on the right end and the left end of the valvespool are balanced.

The valve spool movement to the left (balanced) position reduces the flow of oil to the engagedclutch. The Transmission/Chassis ECM sends a constant maximum specified current signal tothe solenoid to maintain the desired clutch pressure.

NOTE: The lockup clutch valve is calibrated with Cat ET.


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The transmission modulating valves control the oil to corresponding transmission clutches. Oilpressure for the modulating valves can be checked at the tap on top of each valve. Thesolenoid valves are:

- Clutch No. 1 Solenoid valve (1)






The transmission hydraulic oil temperature sensor (7) sends a signal to theTransmission/Chassis ECM indicating transmission oil temperature.


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80

This illustration shows the transmission main relief valve and the torque converter inlet reliefvalve that are located in the transmission control valve body.

The transmission hydraulic control relief valve is used to regulate the pressure to the torqueconverter and the main components in the transmission.

Oil from the transmission pump will move the spool toward the right against spring pressure.The spool directs the oil to the torque converter and to the torque converter inlet relief valve.The main valve spool limits the pressure in the transmission hydraulic system and the torqueconverter inlet relief valve limits the inlet pressure at the torque converter.

Under normal operation, oil from the pump flows past the spool to the torque converter inlet.As the torque converter pressure increases, the torque converter inlet relief valve allows the oilto drain into the transmission case, which controls the torque converter inlet pressure.

When oil is not flowing to the transmission hydraulic control relief valve, the oil between theslug and ball (located inside spool) is trapped and the oil drains slowly past the slug to thetransmission case. As the oil drains, the spool movement is dampened which prevents the spoolfrom returning to the left before the torque converter has stopped rotating.

The adjustment screw alters the preload on the spring to adjust the main relief pressure.


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This illustration shows the access to the main relief valve adjustment screw (arrow). A smallcover on top of the transmission control body must be removed to gain access to the adjustmentscrew.


82

In this illustration, the transmission modulating valve is shown with no current signal applied tothe solenoid. The Transmission/Chassis ECM controls the rate of oil flow through thetransmission modulating valves to the clutches by changing the signal current strength to thesolenoid. With no current signal applied to the solenoid, the transmission modulating valve isDE-ENERGIZED and oil flow to the clutch is blocked.

Pump oil flows into the valve body around the valve spool and into a drilled passage in thecenter of the valve spool. The oil flows through the drilled passage and orifice to the left sideof the valve spool to a drain orifice. Since there is no force acting on the pin assembly to holdthe ball against the drain orifice, the oil flows through the spool and the drain orifice past theball to the tank.

The spring located on the right side of the spool in this view holds the valve spool to the left.The valve spool opens the passage between the clutch passage and the tank passage and blocksthe passage between the clutch passage and the pump supply port. Oil flow to the clutch isblocked. Oil from the clutch drains to the tank preventing clutch engagement.


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In this illustration, the modulating valve is shown with a signal to the solenoid that is below themaximum current. Clutch engagement begins when the Transmission/Chassis ECM sends aninitial current signal to ENERGIZE the solenoid. The amount of commanded current signal isproportional to the desired pressure that is applied to the clutch during each stage of theengagement and disengagement cycle.

The start of clutch engagement begins when the current signal to the solenoid creates amagnetic field around the pin. The magnetic force moves the pin against the ball in proportionto the strength of the current signal from the Transmission/Chassis ECM.

The position of the ball against the orifice begins to block the drain passage of the oil flow fromthe left side of the valve spool to the tank. This partial restriction causes the pressure at the leftend of the valve spool to increase. The oil pressure moves the valve spool to the right againstthe spring. As the pressure on the left side of the valve spool overrides the force of the spring,the valve spool shifts to the right.

The valve spool movement starts to open a passage on the right end of the valve spool for pumpsupply oil to fill the clutch. Oil also begins to fill the spring chamber on the right end of thespool.


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In the initial clutch filling stage, the Transmission/Chassis ECM commands a high current pulseto quickly move the valve spool to start filling the clutch. During this short period of time, theclutch piston moves to remove the clearances between the clutch discs and plates to minimizethe amount of time required to fill the clutch. The ECM then reduces the current signal whichreduces the pressure setting of the proportional solenoid valve. The change in current signalreduces the flow of oil to the clutch. The point where the clutch plates and discs start to touchis called TOUCH-UP.

Once TOUCH-UP is obtained, the Transmission/Chassis ECM begins a controlled increase ofthe current signal to start the MODULATION cycle. The increase in the current signal causesthe ball and pin to further restrict oil through the drain orifice to tank causing a controlledmovement of the spool to the right. The spool movement allows the pressure in the clutch toincrease.

During the MODULATION cycle, the valve spool working with the variable commandedcurrent signal from the Transmission/Chassis ECM acts as a variable pressure reducing valve.

The sequence of partial engagement is called desired slippage. The desired slippage iscontrolled by the application program stored in the Transmission/Chassis ECM.


84

In this illustration, the modulating valve is shown with a maximum current signal commandedto the solenoid. When the modulation cycle stops, the Transmission/Chassis ECM sends themaximum specified current signal to fully engage the clutch.

The constant current signal pushes the pin firmly against the ball in the solenoid valve. The pinforce against the ball blocks more oil from flowing through the drain orifice. This restrictioncauses an increase in pressure on the left side of the valve spool, which overcomes the springforce on the right side of the spool. The valve spool moves to the right to allow pump flow tofully engage the clutch.

In a short period of time, maximum pressure is felt at both ends of the proportional solenoidvalve spool. This pressure along with the spring force on the right end of the spool cause thevalve spool to move to the left until the forces on the right end and the left end of the valvespool are balanced.

The valve spool movement to the left (balanced) position reduces the flow of oil to the engagedclutch. The Transmission/Chassis ECM sends a constant maximum specified current signal tothe solenoid to maintain the desired clutch pressure.


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The different maximum specified pressures for each clutch is caused by different maximumcurrent signals being sent by the Transmission/Chassis ECM to each individual modulatingvalve. The different maximum signal causes a difference in the force pushing the pin againstthe ball to block leakage through the drain orifice in each solenoid valve. The different rate ofleakage through the spool drain orifice provides different balance positions for the proportionalsolenoid valve spool. Changing the valve spool position changes the flow of oil to the clutchand the resulting maximum clutch pressure.

The operation of the proportional solenoid to control the engaging and releasing of clutches isnot a simple on and off cycle. The Transmission/Chassis ECM varies the strength of thecurrent signal through a programmed cycle to control movement of the valve spool.


85

This illustration shows the ECPC transmission modulation cycle. The vertical axis representscurrent and clutch pressure. The current represented is from the Transmission/Chassis ECM tothe modulating solenoid valve. The pressure represented is supplied to each individual clutch.When the clutch is filled and the piston is in contact with the plates, the current and pressureare directly proportional, and are represented on the same axis. The horizontal axis representstime in intervals that relate to the hydraulic pressure supplied to the clutch.

The pulse time is caused by an initial high current applied to the valve to begin pressurizing theclutch when a clutch is engaged. The ramp level begins a reduction in the current applied tothe valve which lowers the current to the hold level.

When the current is at the hold level, the clutch is full. The clutch pressure then follows thecurrent applied to the solenoid.

At the end of the hold time, the current increases as the clutch is engaging. This time is calledthe "desired slip time," and the pressure ramp is called "modulation."


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Modulation continues until the clutch is fully engaged and the maximum clutch pressure isreached. The clutch pressure stays at maximum for a short time called the "full on time." Theclutch pressure is then reduced to the clutch engagement level. The clutch is still fullyengaged, but at a lower pressure. This pressure reduction increases clutch seal life.


86

Transmission system calibration provides a method to update the application program table ofthe Transmission/Chassis ECM. Calibration identifies the current for the "Hold Level" anddetermines when to fill the clutch. Calibration also compensates for transmission oiltemperature when filling the clutch. The correct clutch fill time can affect the transmission shiftquality.

The clutch fill calibration procedure is used to update the application table in the ECM memory(Note "Application Table" area of graph). This step is an automatic procedure performed by theTransmission/Chassis ECM based on the maximum clutch current values.

Transmission calibration is performed automatically by the Transmission/Chassis ECM, but canalso be performed, if necessary, with Messenger or Cat ET.


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Calibration procedures should be performed whenever one or more of the following conditionsoccur:

- Initial transmission installation

- Transmission/Chassis ECM replacement

- Transmission modulating valve replacement

- Transmission main relief valve replacement

- Transmission replacement

- Transmission pump replacement

- Oil cooler replacement

- Poor shift quality

The transmission calibration is successful when there is no noticeable change in shift quality.


87

This illustration shows a sectional view of the planetary transmission. The planetarytransmission provides six forward speeds and three reverse speeds. The transmission containssix clutches which are engaged hydraulically and released by spring force.

A speed clutch and a direction clutch must be engaged in that sequence to send power throughthe transmission.

The No. 1 clutch, the No. 2 clutch, and the No. 3 clutch are direction clutches and are closest tothe input end of the transmission. The No. 1 clutch is the REVERSE DIRECTION clutch, theNo. 2 clutch is the FORWARD LOW direction clutch and the No. 3 clutch is the FORWARDHIGH direction clutch. The No. 4 clutch, the No. 5 clutch, and the No. 6 clutch are the speedclutches.


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The table in this illustration lists the solenoids that are energized and clutches that are engagedfor each transmission speed. This table can be useful for transmission diagnosis.


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Differential Lock

These illustrations show the components in the differential lock system. The differential lockpump (1) is mounted to the brake/fan pump (2). The differential lock pump supplies oilthrough the differential lock filter (3) to the differential solenoid (4). The differential lock filteris located on the right side of the machine.

The differential lock solenoid is located on the left rear side of the differential case. Thedifferential lock solenoid is turned off and on by the differential lock relay located in the cabfuse panel. The relay is turned off and on by the differential lock switch located on the rightoperator joystick.

The differential lock relief valve (5) is located on the right side of the machine near thedifferential lock filter. The relief valve limits pressure in the differential lock system.

The differential lock filter has a bypass switch (6) which provides an input signal to themonitoring system, via the Transmission/Chassis ECM, to inform the operator if the filter isrestricted. Differential lock system pressure can be checked at the pressure tap (7) located onthe filter housing.

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90

The differential is equipped with a hydraulically engaged differential lock (1) which improvestraction in poor underfoot conditions. The differential lock uses a clutch pack (2) to lock onedifferential side gear to the spider gear case.

The final drives are also located in the same case as the differential. The final drives use gearsto multiply the torque before it reaches the wheels.


12

91

This illustration shows the oil flow through the differential lock system when the differentiallock system is in the LOCK position.

The differential lock pump supplies oil through the differential lock filter to the differentialsolenoid.

When the differential lock switch on the joystick is activated, a signal is sent to theTransmission /Chassis ECM. The ECM sends a corresponding signal to the differential lockrelay in the cab. The relay energizes the differential lock solenoid. The solenoid moves upagainst spring force and directs oil to the differential lock. The differential lock clutch pack isengaged and the differential is LOCKED.

The differential lock relief valve limits pressure in the differential lock system.


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92

IMPLEMENT AND STEERING SYSTEM

The "M" Series Motor Graders are equipped with a Priority Proportional, PressureCompensated (PPPC) implement electrohydraulic system. The PPPC system will sense ademand for flow and the implement pump and implement/steering pump will upstroke ordestroke to provide the necessary flow. The steering system is an electrohydraulicallycontrolled system. The Implement ECM, Transmission/Chassis ECM, and steering controlvalve all work together to provide a primary steering system and a secondary steering system.

The following main components make up the implement and steering systems:

- Implement ECMs

- Left and right electronic joysticks

- Implement pump

- Implement/steering pump

- Pilot control manifold

- PPPC electrohydraulic control valves


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- Secondary steering pump

- Secondary steering solenoid valves

- Steering control valve

- Implement and steering cylinders

- Hydraulic tank

The implement pump provides oil to the pilot control manifold and to the implement controlvalves. The implement/steering pump supplies oil to the priority valve. The priority valvedivides the oil flow between the implement and steering circuits.

The pilot control manifold contains the main relief valve, a pressure reducing valve, and thepilot shutoff valve. The main relief valve limits oil pressure in the implement/steeringhydraulic system. The pressure reducing valve reduces implement circuit pressure to be usedfor the pilot oil circuit. The pilot shutoff valve controls the pilot oil flow to the implementcontrol valves.

Pilot oil controls the steering solenoids and the implement solenoids. When energized by theImplement ECM, the steering and implement solenoids control pilot oil to the appropriatedirection spool. The direction spool directs implement/steering pump oil to the correspondingimplement or steering cylinder.

The joysticks, implement lockout switch, and steering cylinder position sensors provide inputsignals to the Implement ECM. The ECM processes the input signals and sends correspondingoutput signals to the steering solenoids, the implement solenoids, and the pilot shutoff valve.

The secondary steering solenoids are used as a back-up in case the primary steering controlsolenoids fail.

The ground-driven secondary steering pump is used to provide oil flow to the implement andsteering system in the event of a dead engine or a primary implement/steering pump failure.


The Implement ECMs are located in the cab, behind the operators seat. The 24M Motor Graderis equipped with two Implement ECMs.

Implement ECM (1): This ECM is the primary Implement ECM. All diagnostic codes areactivated by this control module under the module identifier 082. The other implement controlmodules communicate diagnostics over the CAN Data Link (J1939) to the Implement ECM (1)which will activate diagnostic codes and events when necessary. The primary Implement ECMhandles all joystick inputs.

Implement ECM 2 (2): This ECM is a secondary Implement ECM that handles all standardimplement and steering outputs. This ECM will receive inputs from the primary ImplementECM via the CAN Data Link (J1939) and auxiliary control pod. The secondary ECM will sendoutputs to attachment auxiliary control valves 1, 2, and 7, if equipped.

93


1 2

94

Implement Electrical System

Input Components:

Operator Present Switch: An input to the ECM that indicates if an operator is in theoperator’s seat.

Key Start Switch: Provides a signal to the Implement ECM when the operator wants to startthe engine.

Hydraulic Oil Temperature Sensor: An input to the ECM with the temperature of thehydraulic oil.

Pilot Filter Bypass Switch: An input to the ECM when the pressure is above 172 kPa (25 psi)in the oil filter.

Secondary Steering Test Switch: An input to the ECM that indicates when the operator wantsto test the secondary steering motor and pump.

Hydraulic Pump Pressure Sensor: An input to the ECM that provides the pressure in thesteering and implement hydraulic system.


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Steering Valve Control Module: The control module for the steering valve provides twoinputs to the Implement ECM. The control module provides a spool position signal and anerror signal to the ECM.

Left Joystick: Provides 12 different inputs to the Implement ECM. Some of those inputsinclude: wheel lean right, articulate right, and steering.

Right Joystick: Provides 5 different inputs to the Implement ECM. Some of those inputsinclude: blade sideshift, circle sideshift, and blade tip.

Right Steering Cylinder Position Sensor: Signals the ECM the position of the rod in thesteering cylinder.

Left Steering Cylinder Position Sensor: Signals the ECM the position of the rod in thesteering cylinder.

Articulation Angle Sensor 1 and 2: Signals the ECM the angle of the rear frame as comparedto the angle of the front frame.

Implement Lockout Switch: Sends an input signal to the ECM to de-energize the implementpilot solenoid to protect from inadvertent movement of the implements.

+24 Battery Voltage: Unswitched power supplied to the Transmission/Chassis ECM from thebattery.

Location Code 2: The location code pin number 2 is a grounded input signal that establishesthe ECM is dedicated to power train and chassis operations. J1-27 pin on theTransmission/Chassis ECM connector is grounded.

Location Code Enable (GND): The location code enable is a grounded input signal to theTransmission/Chassis ECM that enables the location code enable feature. J1-32 pin on theTransmission/Chassis ECM connector is grounded.

Output Components:

Implement Pilot Solenoid: This ON/OFF solenoid valve is an output from the ImplementECM. This valve opens the flow of pilot oil to the implement control valves.

Blade Left Raise/Lower Solenoids: The proportional solenoid valves are an output from theImplement ECM. The solenoid valve sends a proportional amount of pilot oil to the bladeraise/lower spool depending on the amount of current applied to the solenoids.

Blade Right Raise/Lower Solenoids: The proportional solenoid valves are an output from theImplement ECM. The solenoid valve sends a proportional amount of pilot oil to the bladeraise/lower spool depending on the amount of current applied to the solenoids.

Articulate Left/Right Solenoids: The proportional solenoid valves are an output from theImplement ECM. The solenoid valve sends a proportional amount of pilot oil to thearticulation spool depending on the amount of current applied to the solenoids.


Wheel Lean Left/Right Solenoids: The proportional solenoid valves are an output from theImplement ECM. The solenoid valve sends a proportional amount of pilot oil to the wheel leanspool depending on the amount of current applied to the solenoids.

Blade Sideshift Left/Right Solenoids: The proportional solenoid valves are an output fromthe Implement ECM. The solenoid valve sends a proportional amount of pilot oil to the bladesideshift spool depending on the amount of current applied to the solenoids.

Circle Drive Clockwise/Counterclockwise Solenoids: The proportional solenoid valves arean output from the Implement ECM. The solenoid valve sends a proportional amount of pilotoil to the circle drive spools depending on the amount of current applied to the solenoid.

Blade Tip Forward/Backward Solenoids: The proportional solenoid valves are an outputfrom the Implement ECM. The solenoid valve sends a proportional amount of pilot oil to theblade tip spool depending on the amount of current applied to the solenoid.

Centershift Left/Right Solenoids: The proportional solenoid valves are an output from theImplement ECM. The solenoid valve sends a proportional amount of pilot oil to the centershiftspool depending on the amount of current applied to the solenoid.

Auxiliary 7 Control Solenoids: The proportional solenoid valves are an output from theImplement ECM. The solenoid valve sends a proportional amount of pilot oil to the auxiliaryspool depending on the amount of current applied to the solenoid.

Steering Valve Control Module: The control valve module for the steering valve is an outputof the Implement ECM. The Implement ECM provides power and a command signal to thecontrol module.

Backlight Relay: The Implement ECM energizes the backlight relay when any of theworklamp switches have been turned to the ON position.

+5 Volt Supply: Power supplied to the components from the Implement ECM.




95

Left Joystick Electronic Operation

The left joystick has fourteen functions as previously described. The gear selection, neutralarticulation, and direction functions use switch type inputs. The wheel lean function uses linearpushbuttons that send a PWM signal to the Implement ECM. The left blade lift, steering, andarticulation functions use Hall cell type sensors that send PWM signals to their correspondingECMs.

NOTE: The joystick is not serviceable. The joystick must be replaced if any switch orsensor fails.

The left joystick contains three steering sensors that are necessary for correct steering operation.All three sensors send a PWM signal to both the Implement ECM and the Transmission/ChassisECM. Steering sensors 1 and 2 are powered from the Implement ECM. Steering sensor 3 ispowered from the Transmission/Chassis ECM.

A Level 3 Warning occurs when any steering lever position sensor fails. The machine willcontinue to steer normally (with an active Level 3 warning) using the two remaining sensors.


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There are some points to consider when diagnosing FMIs for the steering lever positionsensors:

- Verify that CID 0041 (8 volt power supply) for the Implement ECM (MID 082) does nothave any active codes. Correct any problems with the 8 volt power supply if anydiagnostic codes are active.

- The correct operating temperature range for the steering sensors is -40° C (-40° F) to 75° C (167°F). Normalize the cab environment to the acceptable temperature range if anFMI 03 or and FMI 08 code becomes active for a steering sensor when the cabenvironment is at extreme temperatures. Verify an active FMI is still present beforecontinuing to troubleshoot.

- The Transmission Chassis ECM (MID 027) and the Implement ECM (MID 082) receivean input signal from the steering lever position sensors. Both ECMs can activate adiagnostic code for all three sensors. It is likely that the sensor is operating correctly ifone ECM has activated a diagnostic code and the other ECM has not. When this occurs, apoor connection in the machine harness would be suspected. When both ECMs haveactivated the diagnostic code, either the sensor OR a harness problem could be the cause.It is very unlikely that both ECMs have failed when both ECMs have activated thediagnostic code.


96

Right Joystick Electronic Operation

The right joystick has twelve functions as previously described. Throttle resume anddifferential lock are switch type inputs. The remaining functions are PWM inputs. The throttleresume switch input is sent to the Engine ECM and the differential lock switch input is sent tothe Transmission/Chassis ECM. All other inputs from the right joystick are sent to theImplement ECM. Power to the right joystick is supplied by the Implement ECM and theTransmission/Chassis ECM.

NOTE: The joystick is not serviceable. The joystick must be replaced if any switch orsensor fails.

The right joystick receives power from the Implement ECM and the Transmission/ChassisECM. The correct Module Identifier (MID) must be identified when troubleshooting a CID1482 (10 volt power supply).

There are some points to consider when diagnosing FMIs for the right joystick:

- Verify that CID 1482 (10 volt power supply) for the Implement ECM andTransmission/Chassis ECM does not have any active codes. Correct any problems withthe 10 volt power supply if any diagnostic codes are active.


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97


The hydraulic tank (1) is located on the left side of the machine. There are two return filters (2) that remove any debris in the hydraulic oil before the oil returns to the hydraulic tank.The return filters are located on the rear of the tank one on the left and one on the right side ofthe tank. A case drain filter (3) is located on the right side of the machine.

The return filters and case drain filters include a filter bypass valve. Each filter also includes afilter bypass switch that is monitored by the Transmission/Chassis ECM. The filter bypass willallow dirty oil to flow to the hydraulic tank if the filter element becomes plugged. Follow therecommended service intervals for the return filter.

Each return filter also includes an S•O•S tap (4) and a pressure tap (5) for checking return filterbypass pressure. The case drain filter includes a pressure tap (6) for checking case drainpressure.

The hydraulic oil level can be checked at the sight glass (7) on the side of the tank.

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The 24M is equipped with two identical variable displacement piston pumps for the implementand steering systems. The pumps are mounted in tandem to the pump drive on the right side ofthe machine.

The implement/steering pump (1) supplies oil to the implement and steering systems and isattached to the pump drive. The implement pump (2) supplies oil to the implement system andis mounted to the implement/steering pump.

Both pumps contain a pump control valve (3) to allow the pump to vary the amount of flow thatis produced. The pressure tap (4) is installed in the signal line at the pump control valve. Thepressure tap provides a location to test the signal pressure of either the steering signal orimplement signal.

The hydraulic pump pressure sensor (5) sends a signal to the Implement ECM indicatingimplement/steering pump pressure.

98


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The implement and steering control manifold, mounted on a bracket attached to thetransmission, contains the following components:

Pressure tap (1): This tap is used for testing the pressure at the outlet of the implement andsteering pump.

Pressure reducing valve (2): This valve limits the pressure in the implement pilot circuit. Thepressure reducing valve is adjustable.

Relief valve (3): This valve protects the implement and steering supply circuit from highpressure. The relief valve is adjustable.

Implement pilot solenoid (4): This solenoid directs or prevents oil flow to the implement pilotsystem. The implement lockout switch in the cab energizes or de-energizes this solenoid.Supply oil will be directed to the implement pilot system when this solenoid is energized. Nooil will be directed to the implement pilot system when the solenoid is de-energized.

S•O•S port (5): This port is used for pulling an oil sample from the outlet of the implementand steering pump.

Pressure tap (6): This tap is used for testing the pressure in the pilot system.

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The pilot oil filter (1) removes any debris from the oil before the oil travels to the pilot system.The pilot filter is located on the right side of the machine near the hydraulic tank.

The pilot oil filter has a bypass switch (2) that is monitored by the Implement ECM. Pilot oilpressure can be checked at the pressure tap (3) located on the base of the filter.

Also visible in this illustration is the return oil filter (4).

100


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The steering control valve (1) is located on the left side of the frame below the cab. Thesecondary back-up steering solenoids (2) are located above the steering control valve.

The steering control valve is an electro-hydraulic valve that consists of a hydraulic section (3)and an electronic section (4). The hydraulic section has a priority valve that will ensure that thesteering circuit demands are met before any hydraulic oil is sent to the implement circuit. Thehydraulic section also has a pressure reducing valve that will meter pilot oil to the secondaryback-up steering solenoids. The main function of the steering control valve is to direct pumpsupply oil to the steering cylinders when the operator requests a turn with the left joystick. Thesteering control valve has several other internal components that will be discussed in moredetail with a schematic.

101

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The steering control valve electronic section is controlled by the Implement ECM. TheImplement ECM will send a control signal to the steering control module when the left joystickchanges positions (operator requests a steer left or right). The steering control module willdirect pilot oil to move the directional control spool inside the steering control valve onedirection or another. The steering cylinders will begin to move. The ECM will monitor theposition of the steering cylinders and the position of the directional control spool inside thesteering control valve. The Implement ECM will decrease the control signal to the steeringcontrol module as the steering cylinders approach the desired position. The steering controlmodule also has an LED (5) which displays the operational status of the module.

The Implement ECM will not allow the steering system to function until certain conditions aremet. The conditions are as follows:

- Engine operating

- Sufficient hydraulic system pressure

- Operator present

- Park brake ON, transmission in NEUTRAL

- No steering cylinder faults

Additionally, the left joystick position must be aligned with the angle of the front wheels beforethe Implement ECM will allow the steering system to operate. The operator accomplishes thisby slowly sweeping the joystick to the left or right and aligning the joystick angle to the wheelangle. Other conditions that may prevent the steering system from being enabled are asfollows:

- Sweeping the joystick too fast

- Front wheel position out of range: Sweeping the joystick may not align the joystick to thesteering cylinders if the wheels are out of range (due to damage or extreme angle). Thewheels must be manually moved back into range if this condition occurs. Actuating thewheel lean function left or right may help move the wheels into an acceptable range.


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There are three types of signals that are communicated between the Implement ECM and theSteering Control Valve. The signals are as follows:

- Steering control signal: The steering control signal is a PWM signal sent from theImplement ECM to the steering control module. The duty cycle of the control signal isdependent on the input signals from the steering cylinder position sensors and the leftjoystick position sensor to the Implement ECM. The steering control module will adjustthe position of the directional valve spool based on the duty cycle of the control signal.The Implement ECM does not monitor the control signal circuit for diagnostics. Thesteering control module will detect a problem such as a high or low voltage in the signalcircuit and will send an error signal to the Implement ECM. The Implement ECM willturn the power supply to the steering control module OFF if the steering control modulesends an error signal. The Implement ECM will also send a request to theTransmission/Chassis ECM to activate the secondary steering system.

- Spool position signal: The Implement ECM receives an input from the steering controlmodule that indicates the position of the directional valve spool inside the steering controlvalve. The Implement ECM uses this information to determine if the steering valvecontrol module is responding correctly to the steering control signal. The ImplementECM monitors the spool position circuit for diagnostics. The Implement ECM will turnthe power supply to the steering control module OFF if the ECM detects a high voltagecondition, a low voltage condition, or a short. The Implement ECM will also send arequest to the Transmission/Chassis ECM to activate the secondary steering system in theevent of a steering control valve diagnostic.

103


- Error signal: The steering control module monitors it’s own operation and monitors theImplement ECM circuits that are connected to the module. The steering control modulewill send an error signal to the Implement ECM if the steering control module detectselectrical problems. The Implement ECM will turn the power supply to the steeringcontrol module OFF if the steering control module sends an error signal. The ImplementECM will also send a request to the Transmission/Chassis ECM to activate the secondarysteering system.

The steering control valve is equipped with a status LED. This LED will be green if there areno faults. The LED will flash red if there is an input signal fault. Closed loop faults will causethe LED to be constantly illuminated red.


104

This chart shows the relationship between the command signal percentage, command signalvoltage, supply voltage, and spool position. The chart also shows the linear relationshipbetween command voltage and spool position.


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The "M" series motor graders are equipped with a secondary steering system. TheTransmission/Chassis ECM and the Implement ECM work together to turn on the secondarysteering system if the primary steering system fails. The Transmission/Chassis ECM and theImplement ECM monitor the left joystick, steering cylinder position sensors, pump pressuresensor, and the articulation sensors.

The Implement ECM will send a PWM signal to the Transmission/Chassis ECM if thesecondary steering system needs to be activated due to a secondary steering test or a problem inthe primary steering system. The duty cycle of the PWM signal will be used to determinewhich specific secondary steering component needs to be activated. The PWM duty cycle is asfollows:

- 20 percent PWM duty cycle: Normal operation, no request to activate.

- 40 percent PWM duty cycle: Request to activate the secondary steering pump motoronly.

- 60 percent PWM duty cycle: Request to activate the secondary steering pilot solenoidvalves only.

- 80 percent PWM duty cycle: Request to activate the secondary steering pump motor andthe secondary steering pilot solenoid valves.


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The Implement ECM will send the request signal to activate the secondary steering systemwhen any of the following machine system conditions are detected:

- An active CID 2202 FMI 12 "Steering Valve Control Module Error" diagnostic code ispresent.

- A failure of the main hydraulic pump.

- Steering motion is detected when no primary steering command is present.

- Steering motion is not detected when a primary steering command is present.

- Steering motion is detected in the wrong direction.

- A manual secondary steer test has been requested.

- An automatic secondary steer system test is being performed at initial start up.

NOTE: The secondary steering system is designed to be used for a short period of timeto move the machine to an area where the machine can be safely shut down.


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The Transmission/Chassis ECM will activate the secondary steering pilot solenoid valves (1) or (2) when a 60 percent duty cycle is sent from the Implement ECM. TheTransmission/Chassis ECM will send a PWM output signal to the appropriate solenoid based onthe steering cylinder position sensors signal and the left joystick position sensor signal. Thesecondary steering pilot solenoid will direct pilot oil to one side of the the directional valvespool which is inside the steering control valve. The amount of oil directed to the spool isbased on the duty cycle of the PWM signal sent by the Transmission/Chassis ECM.

The secondary steering system will remain active until the machine is turned OFF. The primarysteering system will be active when the machine is restarted only if the condition that causedthe activation of the secondary steering system is no longer present.

106


The steering control valve (top illustration) has a screen (1) located in the supply port for thesolenoids. The screen helps to protect the solenoids from any debris in the hydraulic system.

The secondary steering manifold (bottom illustration) has a screen (2) located in the supply portfor the secondary steering solenoids. The screen helps to protect the solenoids from any debrisin the hydraulic system.

107

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If the engine stops or the hydraulic pump fails, the secondary steering system can supply oil tothe steering system. The main components in the secondary steering system are secondarysteering pump (1) and the unloading valve (2).

The secondary steering pump is a ground driven gear pump mounted to the bottom of theoutput transfer gear. The pump turns when the machine moves. When the engine is operating,the primary hydraulic pump sends oil through the steering control valve to operate the steeringcylinders.

As the machine starts to move, oil is sent from the secondary steering pump to the unloadingvalve. When flow is present from the primary hydraulic pump, the unloading valve directs oilflow from the secondary pump back to the tank.

The unloading valve includes a relief valve (3) that limits oil pressure in the secondary steeringsystem.

109


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Steering Hydraulic System Operation

The implement and steering pump provides flow to the steering control valve. Supply oil entersthe steering control valve and flows to the priority valve. The priority valve is held to the leftby spring force. The priority valve directs supply oil to the steering circuit until the steeringcircuit is fully charged. Once the steering circuit is fully charged, the priority valve will shift tothe right and direct supply oil to the implement circuit.

The compensator valve directs steering priority oil to several locations. The first location is thepressure reducing valve and the second location is the direction spool. The compensator valvealso has an internal passage that contains two orifices. One internal orifice meters oil to the leftside of the compensator valve. The other internal orifice meters supply oil into the load sensecircuit.

Pump supply oil is blocked when the direction spool is in the HOLD position. Oil in the loadsense circuit is allowed to flow through a passage in the direction spool and to the meteringvalve. The purpose of the metering valve is to maintain enough pressurized oil in an internalpassage to supply the steering control solenoids with enough oil to shift the direction spoolwhen the operator requests a turn.


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The pressure reducing valve directs pump supply oil to the secondary steering controlsolenoids. The pressure reducing valve will block supply oil when the secondary steeringcontrol solenoid circuit reaches about 3000 kPa (435 psi).

The signal relief valve limits the pressure in the signal circuit. The signal relief valve willdirect excess oil to tank if the signal circuit pressure is above the setting of the relief valve.

The crossover relief valves protect the steering cylinders from sudden pressure spikes. Thecrossover relief valves will dump oil from one side of the cylinder to the other if the pressure inthe steering cylinders raises above the setting of the relief valves.

The steering control solenoids work in pairs to shift the direction spool in the steering controlvalve. The lower steering control solenoids block supply oil which is maintained by themetering valve when no steering request is being made by the operator. The upper steeringcontrol solenoids are open to tank when no steering request is being made by the operator.

The secondary steering control solenoids are used as a back-up in case the primary steeringcontrol solenoids fail. The secondary steering control solenoids meter pilot oil to tank whenthe Transmission/Chassis ECM is not energizing one of the secondary steering controlsolenoids.


111

The Implement ECM sends a steering request to the right steering control solenoids when theoperator makes a right turn request. The upper and lower right steering control solenoidsenergize and shift to the left. Pilot oil that is maintained by the metering valve is directed pastthe lower right steering control solenoid and the right shuttle valve to the right side of thedirection spool. The direction spool will shift left and direct pump supply oil to the steeringcylinders. The direction spool will also direct pump supply oil into the load sense circuit toseat the check valve.


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The Transmission/Chassis ECM sends a steering request to the secondary right turn solenoidswhen the operator makes a right turn request and the primary steering solenoids are notfunctioning properly. The top solenoid will energize and shift downward. Pilot oil that ismaintained by the pressure reducing valve is directed through the solenoid, and past a shuttlevalve to the right side of the direction spool. The direction spool will shift left and direct pumpsupply oil to the steering cylinders. Pump supply oil will also seat the check valve in the loadsense circuit after the direction spool has shifted left.


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Implement and Steering System Components

The steering cylinders (arrows) are located at the front of the machine. The steering cylindershave an internal position sensor which allows the Implement ECM and theTransmission/Chassis ECM to monitor the position of the steering cylinders. This signal iscompared to the position of the steering lever sensors for diagnostic purposes.

The steering cylinder position sensors can be changed on the "M" series graders.

NOTE: New cylinder extension and retraction parameters must be entered into Cat ETif a cylinder position sensor is changed.

New software files must be downloaded and flashed into the Implement ECM uponreplacement of a steering cylinder.

NOTE: The steering cylinder position sensors are powered from two different ECMs.The left sensor is powered from the Transmission/Chassis ECM and the right sensor ispowered from the Implement ECM.

113


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The steering cylinders are equipped with position sensors. The sensor sends a Pulse WidthModulated (PWM) signal to the ECM with the cylinder piston position within the piston stroke.

The sensor uses the magnetostrictive principle. A wire is stretched inside the length of thesensor rod in order to form a waveguide. At time zero, a current pulse is transmitted down thewire by the electronics in the sensor head. At the point where the pulse reaches the magneticfield of the magnet, a pulse is generated and sent back to the sensor head. Internal electronicsconvert the time zero to the time it takes the return pulse to reach the sensor head into anelectronic PWM signal. The pulse width is directly proportional to the position of the magnet.The sensor frequency is 500 Hz.

114


The articulation position sensors are located on the front half of the machine in front of thearticulation hitch.

Articulation position sensor 1 (1) is powered by the Implement ECM and is monitored by theImplement ECM and the Transmission/Chassis ECM. Articulation position sensor 2 (2) ispowered by the Transmission/Chassis ECM and is monitored by the Implement ECM and theTransmission/Chassis ECM.

Both machine articulation position sensors must track within 3.5 degrees (angular) of each otheror a FMI 14 will be activated. The cause for this is usually loose, incorrectly assembled, ordamaged linkages.

Tech tip: Using Electronic Technician, check the articulation position sensors’ dutycycle if a CID 615 FMI 14 or a CID 2252 FMI 14 diagnostic code is active. Calibratethe sensors if the duty cycle is within specification. Adjust the mechanical linkage ofthe sensors if the duty cycle is out of specification. Recalibrate the sensors after youadjust the mechanical linkage.

115


1

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Position Angle (Degrees) Duty Cycle (%)

Full Left -20 33

Center 0 55

Full Right 20 74

The implement control valves are located in two places. The top illustration shows theimplement control valve mounted on the left side of the frame below the cab.

The bottom illustration shows the implement control valve mounted on the right side of theframe below the cab.

There are nine standard implement circuits on the machine and ten control valves. Eightcontrol valves are for cylinder circuits and two control valves are for the circle drive motor thatrotates the blade around the drawbar.

116

117


The implement control valves (top illustration) contain the following components:

- ripper control valve (1) - wheel lean control valve (4)

- circle drive control valve (2) - blade lift control valve (5)

- sideshift control valve (3)

The implement control valves (bottom illustration) contain the following components:

- implement signal relief valve (6) - blade tip control valve (9)

- articulation control valve (7) - center shift control valve (10)

- circle drive control valve (8) - blade lift control valve (11)

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The implement control valves use a common supply passage that runs through the center of thevalve. In the HOLD position, supply oil is blocked from entering the valve by the directionspool. The direction spool has metering slots to match the flow requirements of each circuit.

The compensator spool prevents a single circuit from receiving the maximum pump flow whenmultiple circuits are actuated at the same time. Oil that enters the signal network through thesignal network check valves flows behind the compensator spool. The force of the spring plusthe force of the oil in the signal network cause the compensator spools in each activated controlvalve to meter the available flow to the actuated circuit.

The check valves in the implement control valve are used to reduce cylinder drift. The checkvalves will remain closed until pressured oil forces the pistons into the check valves. It isimportant to remember that since the check valves are always seated unless an implement isactuated, that the implement lines will always have trapped oil in them. This trapped oil maybe pressurized even if the machine has sat for some time. Use caution whenever an implementline or cylinder is removed.


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The Implement ECM will send a signal to an implement solenoid when the operator makes aimplement request. The solenoid that energizes will direct pilot oil to the right side of thedirection spool. The pilot oil will shift the direction spool to the left against a spring. The non-energized solenoid will allow the oil on the left side of the direction spool to flow to tank.

Pump supply oil will be directed around the direction spool and past the compensator valve.Some of the supply oil will travel up an internal passage and force the pistons outward. Thepistons will move far enough to unseat the check valves. Pump supply oil will then travel upthe left internal passage to the direction spool. The direction spool will meter the oil intoanother internal passage. The supply oil will continue up past the left check valve and out tothe implement cylinder. The oil that leaves the opposite side of the implement cylinder flowsback to the implement control valve, past the right check valve, to the direction spool. Thedirection spool directs this return oil back to tank.

Supply oil will also unseat the signal network check valve and enter the signal network after itpasses the compensator spool. The signal oil plus spring force will act on the lower side of thecompensator spool when multiple circuits are activated. The signal oil will also travel back tothe pump control valve to signal the pump to produce more flow.


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The Implement ECM will send the maximum signal to the implement solenoid when theoperator makes a FLOAT request. The energized solenoid will direct pilot oil to the left side ofthe direction spool. The pilot oil will fully shift the direction spool to the right against a spring.The non-energized solenoid will allow the oil on the right side of the direction spool to flow totank.

Pump supply oil will be directed around the direction spool and past the compensator valve.The supply oil will travel up an internal passage and force the pistons outward. The pistonswill move far enough to unseat the check valves. A load signal is directed to the pump controlvalve from the implement control valve. The pump is upstroked to meet the demands of thesystem.

The directional spool blocks supply oil from entering the passages out to the cylinders. Withthe directional spool fully shifted to the right, oil from the head end and rod end of the liftcylinders is open to tank. As the machine moves, the lift cylinders move up and down with thecontour of the ground. The check valves allow oil to flow to the lift cylinders when thepressure in the lift cylinders drops below tank pressure.


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Implement Hydraulic System Operation

Two pumps provide oil flow the implement system and one of the pumps also provides oil flowto the steering system. Oil flows from the implement pump to the implement/steering controlmanifold and through the manifold to the implement valves.

The control manifold functions are:

- Provides main relief function for the implement circuit via a main relief valve. The mainrelief valve will direct supply oil to tank if the implement supply circuit pressure raisesabove the setting of the main relief valve.

- Provides supply oil to the pilot circuit at a reduced pressure. The pilot shutoff solenoidand the pressure reducing valve work together to turn the pilot circuit on/off as well ascontrol the pressure in the pilot circuit.

Pilot oil leaves the pilot manifold and flows to a pilot filter. The pilot filter contains a bypassvalve and a pressure switch. The bypass will allow pilot oil to bypass the filter and charge thepilot circuit if the filter becomes plugged. Pilot oil that leaves the pilot filter flows through anorifice to all the solenoids in the implement control valves.


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Implement/steering pump supply oil that flows to the priority valve in the steering controlvalve. The priority valve directs supply oil to the steering circuit first, and once the steeringcircuit is charged, directs the supply oil to the implement circuit.

Supply oil that leaves the steering control valve combines with the implement pump oil andflows through the open-center implement control valves. Once the implement and steeringsystem is fully charged, the implement and steering pump will shift to low pressure standby.

Oil from the implement/steering pump also flows to the secondary steering unloading valve.The unloading valve moves down, which directs secondary steering pump oil to the tank.

A pressure sensor on top of the implement/steering pump sends a signal to the Implement ECMindicating implement/steering circuit pressure.


124

The right wheel lean solenoid will energize when the operator makes a wheel lean right request.The energized wheel lean solenoid will direct pilot oil to the right side of the direction spool.The direction spool will shift left and direct reduced supply oil to the compensator valve. Thesupply oil will shift the compensator to the left against the force of the spring. Supply oil willflow through the compensator, past the direction spool, through a check valve, and to the headend of the right wheel lean cylinder and the rod end of the left wheel lean cylinder.

Some of the supply oil will also enter the signal network. The oil in the signal network willflow to the compensator valves in each control valve. The compensator valve in the wheel leancontrol valve will remain shifted to the left because the signal oil plus the force of thecompensator spring will not overcome the force of the supply oil.

The signal oil will also flow through a shuttle valve between the implement and steering systemand back to the pressure compensator at the implement and steering pump. The signal oil andthe force of the pressure compensator spring will adjust the pump to meet the flowrequirements of the wheel lean circuit.

The signal network has a relief valve that will protect the system from high pressures.


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The operator can activate multiple implement control valves at the same time. When theoperator activates the wheel lean circuit and the circle drive circuit at the same time, thesolenoids will energize and direct pilot oil to the direction spools. The direction spools willshift against the force of the springs.

The circuit with the higher pressure will control the pump and the compensator valves. For thisexample, the wheel lean circuit will have a higher pressure then the circle drive circuit. Thewheel lean direction spool will shift to the left and a pressure drop will occur across thedirection spool. Supply oil will travel to the wheel lean compensator valve and shift the valveto the left. Oil that leaves the wheel lean compensator will flow to the signal network and alsopast the direction spool and out to the head end of the right wheel lean cylinder and rod end ofthe left wheel lean cylinder.

Since the wheel lean circuit has a higher pressure, the wheel lean circuit signal oil will hold allthe other signal check balls closed in the other implement control valves. The wheel lean signaloil will also act on the left side of all the compensator valves in all of the other implementcontrol valves.


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At the same time, the circle drive direction spools have shifted and a pressure drop hasoccurred across the direction spools. Supply oil will travel to the circle drive compensatorvalves and attempt to move the valves. The circle drive compensator will not shift all the waybecause the wheel lean signal oil plus the force of the circle drive compensator spring willcounteract the force of the supply oil. The circle drive compensator will now meter or restrictthe supply oil to the circle drive motors which gives the wheel lean circuit priority. Thecompensator valves will always allow the circuit with the highest loads to have priority.


Variable Float Control

The 24M Motor Grader can be equipped with a variable float control attachment. The variablefloat function allows the operator to vary the downforce on both sides of the blade.

The variable float switch (1) sends an input to the Implement ECM to activate the variable floatfunction. The Implement ECM sends a command to Implement ECM 2 to energize thesolenoids for the variable float control. The variable float dial (2) is used to adjust the bladedownforce on the left side. The variable float dial (3) is used to adjust the blade downforce onthe right side.

126


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The valve manifolds (arrow) control the blade downforce on the left side and the right side ofthe blade. The valve manifolds are located on the frame to the rear of the blade lift cylinders.

127


The blade cushion accumulator (1) for the left side of the blade is located below the cab on theleft side of the machine.

The blade cushion accumulator (2) for the right side of the blade is located below the cab onthe right side of the machine.

128

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This illustration shows the variable float not activated and also the variable float activated.When the variable float is not activated, the float function operates normally.

When the variable float is activated, the operator can vary the amount of blade downforce. TheImplement ECM 2 sends current to the variable float enable solenoid and the variabledownforce proportional solenoid in the valve manifold. The current sent to variable downforceproportional solenoid is determined by the variable float dial located in the cab.

The maximum blade downforce that can be produced is by gravity and the weight of the blade.The operator can reduce the blade downforce by turning the variable float dial. When thedownforce is reduced, Implement ECM 2 increases the current sent to the variable downforceproportional solenoid. With the increased current, the solenoid valve opens allowing the oil toflow from the rod end to the head end of the cylinder.


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BRAKE AND FAN SYSTEM

The brake and fan pump (1) is mounted to the transmission pump (2) on the left side of themachine. The brake and fan pump is a variable displacement piston pump with a pressure andflow compensator valve (3). The piston pump provides oil flow for the brake and fan hydraulicsystems.

131


3

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The combination valve for the brake and fan system is located on the left side of the machine,near the articulation hitch. The combination valve ensures that the braking system has priorityover the fan system. Oil from the combination valve flows to the brake accumulators and to thefan motor.

The priority valve (1) directs most of the oil to the brake system until the brake accumulatorsare fully charged. Once the accumulators have been charged, all of the oil flow is then sent tothe fan motor. The fan speed solenoid (2) controls the amount of signal oil that travels from thefan circuit to the brake and fan pump. The fan speed solenoid is controlled by the EngineECM. The cut-in valve (3) and cut-out valve (4) control the cut-in and cut-out pressure for thebrake system. The pressure tap (5) is used for testing the pressure in the brake and fan system.The Transmission/Chassis ECM uses the pressure sensor (6) to monitor the accumulator chargeoil pressure. The relief valve (7) limits the maximum pressure in the brake and fan system.

132


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The service brake accumulators (arrows) are located behind the cab. The accumulators arecharged by the combination valve, and store the pressurized oil until the operator presses theservice brake pedal or activates the parking brakes. The accumulators then provide the requiredoil flow necessary to engage the service brakes and the parking brakes.

133


The service brake control valve (arrow) is located in front of the operators station. The servicebrake control valve directs the oil from the accumulators to the service brakes.

134


135

Service Brake Valve - Not Activated

The service brake valve has two individual brake ports. Also, the brake valve has twoindividual spools which control the flow of oil to the individual brake ports. The upper brakeport is for the right service brakes and the lower brake port is for the left service brakes. Thepressure at the upper brake port is 207 kPa (30 psi) higher than the pressure at the lower brakeport. Also, the spring force will be proportional to the plunger movement.

The brake control valve is equipped with a check valve. The check valve prevents spikes in thetank port from entering the cavity with the plungers springs and acting on the the plunger andeventually transferring to the brake pedal.

The brake control valve is also equipped with shims that are between the ball retainer and theplunger spring. These shims are used to adjust the maximum pressure that is directed to theservice brakes.


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Service Brake Valve - Activated

In order to initiate the operation of the service brake valve, the operator depresses the brakepedal (not shown). The brake pedal contacts the plunger. The plunger is pushed in thedownward direction against the plunger and return springs. The plunger spring puts adownward force on the ball retainer, the ball, the upper spool, and the lower spool. The rightbrake port will be blocked from the upper tank port. The right brake port will then be open toflow from the system pressure port (from the right brake accumulator). Also, the system oilflows through the orifice and the upper spool passage into the cavity between the upper spooland the lower spool. The oil pressure on the bottom area of the upper piston puts an upwardforce on the upper spool pushing the spool against the plunger spring.

The upper spool moves the lower spool downward compressing the lower return spring. Theleft brake port will then be open to flow from the system pressure port (from the left brakeaccumulator). At this time, the oil flows through the lower spool orifice and the lower spoolpassage into the lower spool spring cavity. The oil pressure on the bottom area of the lowerspool puts an upward force on the lower spool pushing the spool against the upper spool andthe plunger spring. The spool movements are equalized.


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Increasing the downward movement of the plunger will increase the spring force and causepressure at the service brake ports to increase until maximum pressure is reached.

Decreasing the downward movement of the plunger will decrease spring force and causepressure at the service brake ports to decrease. The combination of the return springs and theupward force on the upper and lower spools move the spools upward. When the service brakepedal is fully released, the service brake ports will be open to the tank ports.


The service brakes and parking brakes are located inside the four wheel stations (arrows) at therear of the motor grader. The service brakes are engaged by oil from the accumulators. Thebrakes are cooled by oil in the tandem housing. The parking brakes are engaged by springforce and released by oil pressure.

137


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Each wheel station contains disc brakes that are used as service brakes and parking brakes.

The drive chain turns the sprocket. The sprocket turns the wheel spindle, which rotates thebrake plates. The brake discs are connected to the stationary wheel spindle housing. The drivewheels are connected to the wheel spindle.

When the service brake is engaged, the service brake control valve directs oil to the servicebrake piston. The service brake piston compresses the plates and discs together to slow or stopthe wheel assembly.

When the service brake is released, oil flows back to the tank through the service brake valve.The retraction spring moves the service brake piston to the released position.

When the parking brake is released, the parking brake control valve directs oil to the parkingbrake piston. The parking brake piston moves to the right against spring force to release theparking brakes.

When the parking brake is engaged, oil flows back to the tank through the parking brake valve.Spring force causes the parking brake piston to compress the plates and discs together to keepthe wheel assembly from moving.

138


139


The 24M has two slack adjusters. The left slack adjuster (1) is located on the left side of themachine and the right slack adjuster (2) is located on the right side of the machine.

The slack adjusters compensate for brake disc wear by allowing a small volume of oil to flowthrough the slack adjuster and remain between the slack adjuster and the brake piston underlow pressure. The slack adjusters maintain a slight pressure on the brake piston at all times.

Brake cooling oil pressure maintains a small clearance between the brake discs. The servicebrake oil pressure can be tested at the tap (3) located on top of each slack adjuster.

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140

This illustration shows sectional views of the slack adjuster when the brakes are RELEASEDand ENGAGED.

When the brakes are ENGAGED, oil from the service brake control valve enters the slackadjuster and the two large pistons move outward. Each large piston supplies oil to one wheelbrake. The large pistons pressurize the oil to the service brake pistons and ENGAGE thebrakes.

Normally, the service brakes are FULLY ENGAGED before the large pistons in the slackadjuster reach the end of their stroke. As the brake discs wear, the service brake piston willtravel farther to FULLY ENGAGE the brakes. When the service brake piston travels farther,the large piston in the slack adjuster moves farther out and contacts the end cover. The pressurein the slack adjuster increases until the small piston moves and allows makeup oil from theservice brake control valve to flow to the service brake piston.

When the brakes are RELEASED, the springs in the service brakes push the service brakepistons away from the brake discs. The oil from the service brake pistons pushes the largepistons in the slack adjuster to the center of the slack adjuster. Makeup oil that was used toENGAGE the brakes is replenished from the service brake control valve.


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The spring behind the large piston causes some oil pressure to be felt on the service brakepiston when the brakes are RELEASED. Keeping some pressure on the brake piston providesrapid brake engagement with a minimum amount of service brake control valve travel.

The slack adjusters can be checked for correct operation by opening the service brake bleedscrew with the brakes RELEASED. A small amount of oil should flow from the bleed screwwhen the screw is opened. The small flow of oil verifies that the spring behind the large pistonin the slack adjuster is maintaining some pressure on the service brake piston.


141

Brake and Fan System Hydraulic Operation

The brake and fan pump will begin to charge the brake and fan system when the brakeaccumulators drop below the cut-in pressure. The brake and fan pump is upstroked by aninternal spring.

Pump supply oil flows from the pump to the combination valve. Inside the combination valve,oil flows to the priority valve, the fan speed solenoid, through a check valve and orifice, and tothe cut-in valve. The cut-in valve will be shifted upward which will allow signal oil to travelthrough a resolver valve back to the pump flow control valve. The signal oil plus the force ofthe flow control spool spring will ensure that the pump will stay upstroked until the brakeaccumulators are charged. The signal oil also holds the priority valve closed. Supply oil willmeter through an internal orifice in the combination valve and flow around the priority valve.This metered oil will cause the fan to turn at minimum speed.

The supply oil that flows through the check valve and orifice will travel to the inverse shuttlevalve which maintains equal pressure in the accumulators by directing supply oil to theaccumulator with the lowest pressure.

The fan speed solenoid will be fully energized and allow any oil in the fan signal circuit to bemetered to tank.


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The combination valve also has a relief valve to limit brake system pressure and a pressureswitch to monitor the accumulator charge pressure.


142

The cut-out valve will open when the accumulators reach the cut-out pressure. The cut-outvalve will open the bottom side of the cut-in valve to tank which will allow the fully chargedaccumulator circuit to force the cut-in valve downward against the force of the spring.


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The cut-in valve will open the lower spring side of the cut-in valve chamber to tank when it isshifted downward. This will allow the cut-out valve to close, however, the cut-in valve willstay shifted downward. The cut-in valve will remain shifted downward until the spring on thelower side overcomes the force of the oil in the accumulator circuit.


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The fan system will have priority once the brake circuit is fully charged. If the machinerequires maximum cooling, the Engine ECM will decrease the signal to the fan speed solenoid.The spring on the left side of the solenoid will force the solenoid to the right, which willincrease the signal to the pump. The pump flow control valve spring plus the signal from thefan speed solenoid will shift the pump flow control valve to the left. The pump flow controlvalve will drain the oil out of the pump actuator and the internal spring of the pump willupstroke the swashplate. The priority valve will open and the larger volume of oil will increasethe fan speed.

The temperature sensor sends an input signal to the Engine ECM which monitors the fansystem.


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The accumulators store pressurized oil until the operator is ready to apply the service brakes.The brake control valve shifts downward, when the operator presses the brake pedal. The brakecontrol valve will direct pressurized oil from the accumulators to the service brakes. Theservice brakes will slow the machine.


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Parking Brake System

The parking brake is spring applied and hydraulic released, as previously described.

The park brake control valve is located below the rear of the cab. The parking brake controlvalve solenoid (1) controls oil from the brake accumulators to engage and release the parkingbrakes.

A relief valve (2) limits pressure in the parking valve circuit.

The Transmission/Chassis ECM uses a pressure switch (3) to monitor the parking brakepressure.

146


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This illustration shows the parking brake circuit in the RELEASED position.

The parking brake solenoid is energized when the operator turns the parking brake switch off.When the solenoid is energized, oil is directed from the brake accumulators to the parkingbrake in the wheel housings. The oil compresses the parking brake spring, and releases theparking brake.

The joystick must be aligned to the steering wheels to release the parking brake. A level 2warning will be active if an attempt is made to release the parking brake without alignment ofthe joystick and steering wheels.

When the parking brake switch is on, the parking brake solenoid is de-energized and thesolenoid directs oil from the parking brake to the hydraulic tank. The parking brake engages.

NOTE: The machine can be moved without releasing the parking brake. The joystickand wheels must be aligned before the machine can be placed into gear. A Level 3Warning will be active when the machine is in gear with the parking brake engaged.


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The parking brake retraction system can be used to release the parking brake if the brake/fanpump fails or the engine won't run.

When the parking brake retraction switch (1) is activated, power is transferred to the parkingbrake retraction relay (2), which is located on the left side of the engine. The parking brakeretraction relay transfers power to the parking brake retraction motor (3). The electric motordrives the pump (4), which provides oil flow to the parking brake control valve.

With oil flow to the parking brake control valve and the parking brake switch activated, theparking brakes can be released.

The parking brake retraction switch also sends a signal to the Transmission/Chassis ECMindicating the brake retraction system has been activated.

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This illustration shows the parking brake circuit in the RELEASED position using the brakeretraction pump.

When the parking brake retraction switch in the cab is activated oil from the brake retractionpump flows to the brake accumulators.

The parking brake solenoid is energized when the operator turns the parking brake switch off.When the solenoid is energized, oil from the brake retraction pump is directed from the brakeaccumulators to the parking brake in the wheel housings. The oil compresses the parking brakespring, and releases the parking brake.


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Fan System

The fan motor (arrow) is located at the back of the machine. The fan motor is an gear-typemotor with an makeup valve that prevents the motor from cavitation when the machine is shutoff.

150


The hydraulic oil cooler (1) is mounted between the radiator and the front of the engine. Theoil cooler cools the hydraulic oil before it returns to the hydraulic tank.

The hydraulic oil circuit has a temperature sensor (2) that monitors the oil temperature before itenters the cooler. The temperature sensor is an input to the Implement ECM. The ImplementECM sends the temperature reading to the Engine ECM. The Engine ECM uses thisinformation to control the fan speed solenoid.

151

152


1

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CONCLUSION

This presentation provides information on the system operation of the operator’s station, engine,power train, implement, steering, fan, and brake systems.

Always use the latest Service Information to ensure that the most current specifications and testprocedures are used.

153


HYDRAULIC SCHEMATIC COLOR CODE

This illustration identifies the meanings of the colors used in the hydraulic schematics and cross-sectional views shown throughout this presentation.


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1. Machine view (left side)2. Operator’s station3. Dash gauges4. Instrument cluster5. Left electronic joystick6. Horn button and turn signal switch7. Left joystick controls8. Right joystick controls9. Joystick decals

10. Ripper control lever11. Cab switches12. Window wiper switches13. Secondary steering test switch14. Fuse panel15. Circuit breakers and Cat ET connector16. Cab components17. Operator's seat18. Messenger main menu selections19. Performance menu selection20. Totals menu selections21. Settings menu selection22. Service menu selections23. ECM architecture24. C18 ACERT™ engine25. Engine electronic control system26. Fuel delivery system block diagram27. Engine component locations28. Speed timing sensors29. Atmospheric pressure sensor30. Fuel filters31. Fuel pump relay cover32. Engine coolant temperature sensor33. High coolant temperature derate34. Engine oil pressure sensor35. Low oil pressure36. Turbocharger outlet pressure sensor37. Intake manifold air temperature sensor38. Engine intake manifold temperature

derate39. Turbocharger inlet pressure sensor40. Air inlet restriction derate41. Differential fuel pressure switch42. Fuel temperature derate43. Fuel filter restriction derate44. Virtual exhaust temperature derate45. Ether solenoid

46. Radiator47. Throttle mode switch48. Resume/decelerate switch49. Throttle position sensor50. Ground level shutdown switch51. Fan solenoid52. Engine idle management53. Engine compression brake54. Engine compression brake basics55. Engine brake - DISABLED56. Engine brake - ENABLED AND

BEFORE TDC57. Engine brake - ENABLED AND

PISTON AT TDC58. Engine brake - ENABLED AND

PISTON AFTER TDC59. Engine compression brake schematic60. Power train power flow61. Transmission/Chassis ECM62. Transmission/Chassis electrical system63. Secondary steering test switch64. Upshift and downshift switches65. Differential lock switch66. Autoshift switch67. Brake pedal68. Transmission input speed sensor69. Transmission output speed sensors70. Engine start relay71. Differential lock relay72. Transmission hydraulic system -

NEUTRAL73. Power train hydraulic system

components74. Transmission oil filter75. Outlet relief valve76. Torque converter lockup clutch valve77. Lockup clutch modulating valve -

TORQUE CONVERTER DRIVE78. Lockup clutch modulating valve -

DIRECT DRIVE79. Transmission solenoid valves80. Transmission control valve81. Access to main relief valve adjustment

screw82. Transmission modulating valve - NO

COMMANDED SIGNAL

VISUAL LIST


83. Transmission modulating valve -COMMANDED SIGNAL BELOWMAXIMUM

84. Transmission modulating valve -COMMANDED SIGNAL ATMAXIMUM

85. Transmission modulation cycle86. Clutch calibration87. Transmission components88. Transmission clutch engagement chart89. Differential lock system components90. Differential lock91. Differential lock system schematic -

LOCKED92. Implement and hydraulic system93. Implement ECMs94. Implement electrical system95. Left joystick electronic operation96. Right joystick electronic operation97. Hydraulic tank and oil filters98. Implement and implement/steering

pumps99. Implement and steering control manifold100. Pilot oil filter101. Steering control valve102. Electrohydraulic valve103. Electronic primary steering control104. Steering control valve operation105. Transmission/Chassis ECM secondary

steering control106. Secondary steering pilot solenoid valves107. Steering control valve108. Secondary steering manifold screen109. Secondary steering pump110. Steering control valve - LOW

PRESSURE STANDBY111. Steering control valve - PRIMARY

STEER RIGHT TURN112. Steering control valve - SECONDARY

STEER RIGHT TURN113. Steering cylinders114. Steering cylinder sensors115. Articulation position sensors

116. Implement control valve (left side offrame)

117. Implement control valve (right side offrame)

118. Implement control valve components119. Implement control valve components120. Implement control valve - HOLD121. Implement control valve - RAISE122. Implement control valve - FLOAT123. Implement hydraulic system - HOLD124. Implement hydraulic system - WHEEL

LEAN ACTIVATED125. Implement hydraulic system - TWO

IMPLEMENT CONTROL VALVESACTIVATED

126. Variable float control127. Valve manifolds128. Blade cushion accumulator (left side of

blade)129. Blade cushion accumulator (right side of

blade)130. Hydraulic system variable float131. Brake and fan pump132. Combination valve133. Service brake accumulators134. Service brake control valve135. Service brake valve - NOT ACTIVATED136. Service brake valve - BRAKES

ACTIVATED137. Service brake/parking brake wheel

stations138. Wheel station139. Slack adjusters140. Brake slack adjuster141. Brake and fan system - CUT-IN142. Brake and fan system - CUT-OUT

VALVE OPENING

VISUAL LIST


143. Brake and fan system - CUT-OUT/FANAT MINIMUM SPEED

144. Brake and fan system - CUT-OUT/FANAT MAXIMUM SPEED

145. Brake and fan system - SERVICEBRAKES APPLIED/FAN ATMAXIMUM SPEED

146. Parking brake control valve solenoid147. Parking brake circuit - ENGAGED148. Brake retraction system components149. Brake retraction system schematic150. Fan motor151. Fan cooler152. Fan circuit temperature sensor153. Model view

VISUAL LIST

Documents

24M Manual