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SERV1835

March 2007

TECHNICAL PRESENTATION

770 (BZZ), 772 (RLB)

OFF-HIGHWAY TRUCKS

INTRODUCTION

Service Training Meeting Guide

(STMG)

GLOBAL SERVICE LEARNING

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770 (BZZ), 772 (RLB) OFF-HIGHWAY

TRUCKS - INTRODUCTION

AUDIENCE

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

CONTENT

This presentation provides basic maintenance information and describes the systems operation

of the monitoring system, engine, power train, steering, hoist and brakes for the 770/772

Off-highway Trucks. The Automatic Retarder Control (ARC) and the Traction Control System

(TCS) are also discussed. This presentation may also be used for self-paced and self-directed

learning.

OBJECTIVES

After learning the information in this meeting guide, the serviceman will be able to:

1. locate and identify the major components in the engine, power train, steering, and

brakes;

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

3. trace the flow of oil through the systems.

REFERENCES

770/772 Operation and Maintenance Manual SEBU7837

770/772 Parts Manual SEBP4095

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" TEMV3004

STMG546 "Graphic Fluid Power Symbols" SESV1546

Estimated Time: 24 Hours

Visuals: 173

Handouts: 28

Form: SERV1835

Date: 3/07

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SUPPLEMENTAL MATERIAL

Reference Manuals

Fluid Power Graphic Symbols User's Guide SENR3981

Cold Weather Recommendations for Caterpillar Machines SEBU5898

Caterpillar Machine Fluids Recommendations SEBU6250

Salesgrams and Product Bulletins

Training Bulletin "Caterpillar Transmission/Drive Train Oil" TEJB1002

Product Bulletin "Reporting Particle Count By ISO Code" PEJT5025

Salesgram "Caterpillar Extended Life Coolant" TEKQ0072

Product Data Sheet "Caterpillar Extended Life Coolant" PEHP4036

Technical Instruction Modules on Legacy DVDs SERV1000-01(These materials CANNOT be ordered separately.)

Automatic Retarder Control System SEGV2593

Automatic Electronic Traction Aid SEGV2585

769C - 793B Off-highway Trucks--Suspension System SEGV2599

Truck Payload Measurement System SEGV2579

Service Training Meeting Guides

STMG 1751 "769D/771D/773E/775E Off-highway Trucks" SERV1751

Video Tapes

Suspension Cylinder Charging TEVN2155

TPMS Management/Technical Information AEVN2211

TPMS Operating Tips AEVN2212

Introduction to the Automatic Electronic Traction Aid SEVN9187

Mining Trucks--Cleanliness and Component Life SEVN4142

Oil Sampling--The Right Way PEVN4638

Booklets

Know Your Cooling System SEBD0518

Diesel Fuels and Your Engine SEBD0717

Oil and Your Engine SEBD0640

Understanding The S•O•S Report TEJB1015

SERV1835 - 3 - Text Reference

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SUPPLEMENTAL MATERIAL (Continued)

Special Instructions

Accessing Flash Software for Machines REHS0494

Caterpillar Electronic Controls Service Code Information Description List REHS0126

Using the 7X1700 Communication Adapter Group SEHS9264

Using the 261-3363 Wireless Communications Adapter NEHS0926

Use of CE Connector Tools SEHS9065

Servicing DT Connectors SEHS9615

Parts Listing Of The Deutsch Connectors And Components REHS0148

Use of 6V3000 Sure-Seal Repair Kit SMHS7531

Use of 8T5200 Signal Generator/Counter Group SEHS8579

Suspension Cylinder Servicing SEHS9411

770/772 Assembly Procedure REHS1838

Brochures

Caterpillar Electronic Technician NEHP5614

Caterpillar DataView NEHP5622

Diesel Engine Oil (CH4) Product Data Sheet PEHP8038

How to Take a Good Oil Sample PEHP6001

S•O•S Coolant Analysis PEHP5033

Air Filter Service Indicator PEHP9013

Cat Oil Cooled, Multiple Disc Brakes AECQ5980

Caterpillar Automatic Retarder Control AEDK0075

Caterpillar Truck Frames AEDK0707Mining Truck Bodies: Selecting The Right Body System For Your Job AEDK0083

Caterpillar Truck Production Management System: Answering your

questions about TPMS AEDK2953

Miscellaneous

Pocket Card "Electronic Diagnostic Codes" NEEG2500

Chart "Practical Pressure Conversions" SEES5677

"Cleaning Rear Axle Housing Assemblies (785/789)" SEBF8366

Training CD-ROM "Caterpillar Electronic Technician (ET)for Off-highway Trucks" SERV7003

Training CD-ROM "Truck Production Management System (TPMS)

for Off-highway Trucks" SERV7004


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TABLE OF CONTENTS

INTRODUCTION ........................................................................................................................7

MAINTENANCE .......................................................................................................................12

OPERATOR'S STATION............................................................................................................34

MONITORING SYSTEM..........................................................................................................42

Messenger Display Module ..................................................................................................45

ENGINE......................................................................................................................................58

Engine Electronic Control System .......................................................................................60

Engine Derates......................................................................................................................71

Cooling System.....................................................................................................................77

Lubrication System...............................................................................................................85Fuel System...........................................................................................................................86

Air Intake and Exhaust System ............................................................................................90

POWER TRAIN .........................................................................................................................97

Power Train Hydraulic System.............................................................................................99

Rear Axle ............................................................................................................................122

Transmission/Chassis Electronic Control System..............................................................123

STEERING SYSTEM ..............................................................................................................134

HOIST SYSTEM......................................................................................................................146

BRAKE SYSTEM ....................................................................................................................165

Automatic Retarder Control (ARC) ...................................................................................194

Traction Control System (TCS)..........................................................................................196

CONCLUSION.........................................................................................................................203

VISUAL LIST ..........................................................................................................................204

HYDRAULIC SCHEMATIC COLOR CODE.........................................................................207

HANDOUTS.............................................................................................................................208


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NOTES


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INTRODUCTION

Shown is the right side of a 772 Truck. The hydraulic tank is located on the right side of the

truck. The 770/772 Off-highway Trucks are a direct replacement for the 769D/771D

Off-highway Trucks.

The 770/772 Trucks come standard with oil-cooled multiple disc brakes in the rear and caliper

type disc brakes in the front.

The major features added to the 770/772 Trucks are: a new cab, the Messenger monitoring

system, the Tier 3 compliant C15 ACERT™ engine (770), the Tier 3 compliant C18 ACERT™

engine (772), the cooling system, and the hydraulic brakes.

The air system has been eliminated on the 770/772 Trucks. The brakes are completely

hydraulic.

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770 (BZZ), 772 (RLB) OFF-HIGHWAY TRUCKS

INTRODUCTION

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Specifications for the 770 Truck are:

- Serial No. Prefix: BZZ

- Empty weight: 34,520 kg (76,103 lbs)

- Load carrying capacity: 36.3 metric tons (40 tons)

- Gross Machine Weight (GMW): 71,214 kg (157,000 lbs)

- Length: 8.96 m (28.4 ft.)

- Width: 4.78 m (15.7 ft.)

- Height: 4.2 m (13.8 ft.)

- Rated power (with fan): 355 kW (476 hp)

- Maximum ground speed: 74.9 km/h (46.5 mph)

Specifications for the 772 Truck are:

- Serial No. Prefix: RLB

- Empty weight: 35,715 kg (78,738 lbs)

- Load carrying capacity: 45 metric tons (50 tons)

- Gross Machine Weight (GMW): 82,100 kg (181,000 lbs)

- Length: 8.96 m (29.4 ft.)

- Width: 4.78 m (15.7 ft.)- Height: 4.26 m (14 ft.)

- Rated power (with fan): 399 kW (535 hp)

- Maximum ground speed: 79.7 km/h (49.5 mph)


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Shown is the left side of a 772 Truck. The fuel tank is located on the left side of the truck.

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Shown is the front of a 772 Truck. The 770/772 Trucks use a Next Generation Modular

Radiator (NGMR). Its modular design, similar to the previous folded core radiator, permits

easy removal of a single core without having to remove the entire radiator.

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Shown is the rear of a 772 Truck. Two body options are available for the 770/772 Trucks:

- A dual-slope steel design with a "V" bottom main floor to reduce shock loading, center

the load, and reduce spills.

- The dual-slope steel body above, with the addition of a rubber liner for increased

resistance to impact and wear.

All internal wear surfaces of the truck body are made with 400 Brinell hardness steel. The steel

attachment body liner is also made with 400 Brinell hardness steel. The external components of

the body are made of steel with a yield strength of 6205 bar (90000 psi). The rubber liner is

one-fifth the density of steel, but absorbs impact four times better. The rear suspension

cylinders absorb bending and twisting stresses rather than transmitting them to the main frame.

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5

MAINTENANCE

Before working on or operating the truck, read the Operation and Maintenance Manual

thoroughly for information on safety, maintenance, and operating techniques.

Safety precautions and Warnings are provided in the manual and on the truck. Be sure to

identify and understand all symbols before starting the truck.

The first step to perform when approaching the truck is to make a thorough walk around

inspection. Look around and under the truck for loose or missing bolts, for trash build-up, and

for coolant, fuel, or oil leaks. Look for indications of cracks. Pay close attention to high stressareas as shown in the Operation and Maintenance Manual.


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The following list identifies the items that must be serviced every 10 Hours or Daily.

- Walk-Around Inspection: Check for loose or missing bolts, for leaks, for trash build-up

and cracks in frame structures and for body support pads.

- Backup alarm: test

- Brakes, indicators, gauges: test

- Coolant level

- Engine oil level

- Fuel filter: drain water separator

- Fuel tank: drain water / sediment


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- Hoist and brake oil level

- Seat belt: inspect

- Secondary steering: test

- Steering system oil level

- Transmission and torque converter oil level

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The front wheel bearing oil level is checked and filled by removing the plug (1) in the center of

the wheel bearing cover. The oil should be level with the bottom of the plug hole. The fill plug

is a magnetic plug. Inspect the fill plug weekly for metal particles. If any metal particles are

found, remove the wheel cover and inspect the bearings for wear. When draining the oil, rotate

the wheel so the drain plug (2) is at its lowest position.

The service interval for changing the front wheel bearing oil is 500 hours.

Use Final Drive and Axle Oil (FDAO) or commercial FD-1. As a substitute, Transmission

Drive Train Oil (TDTO) with a commercial TO-4 may be used.

Check the tire inflation pressure. Operating the truck with the wrong tire inflation pressure can

cause heat build-up in the tire and accelerate tire wear. Caterpillar recommends inflating tires

with dry nitrogen instead of air to reduce heat build-up and potential combustion. Nitrogen also

slows rubber deterioration and rim corrosion.

NOTE: Care must be taken to ensure that fluids are contained while performing anyinspection, maintenance, testing, adjusting, and repair of the machine. Be prepared to

collect the fluid in suitable containers before opening any compartment or

disassembling any component containing fluids. Refer to the "Tools and Shop Products

Guide" (Form NENG2500) for tools and supplies suitable to collect and contain fluids

in Caterpillar machines. Dispose of fluids according to local regulations and mandates.

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Check the front suspension cylinders for leaks or structural damage. Check the charge

condition of the front suspension cylinders when the truck is empty and on level ground.

Measure the charge height of the suspension cylinders and compare the dimension with the

dimension that was recorded the last time the cylinders were charged. Recharge the cylinders

with oil and nitrogen if necessary.

Two grease outlet fittings are located on each front suspension cylinder. The grease supply

fittings are located on the opposite side of the suspension cylinder. No grease outlet fittings

should be located on the same side of the suspension cylinder as the grease fill location.

Having an outlet fitting on the same side of the suspension cylinder as the grease fill location

will prevent proper lubrication of the cylinder.

Make sure that grease is flowing from the outlet fittings to verify that the suspension cylinders

are being lubricated and that the pressure in the cylinders is not excessive.

NOTE: For more detailed information on servicing the suspension system, refer to the

Special Instruction "Suspension Cylinder Servicing" (Form SEHS9411).

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Inspect the front brake linings (1) for wear. The thickness of the brake linings (not including

carrier) must not be less than 3.15 mm (.125 in). Measure the lining at both ends because one

end can wear more than the other.

The clearance between the brake carrier guide pins (2) and the brake disc (3) must not be less

than 1.5 ± 0.5 mm (.06 ± .02 in.).

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The engine oil filter (1) is located on the right side of the engine. Engine oil samples can be

taken at the Scheduled Oil Sampling (S•O•S) tap (2) located on the front of the oil filter base.

The engine oil filter can be accessed from below the engine. If the truck is equipped with a

sound suppression system, an access cover (3) must be removed.

Jacket water coolant samples can be taken at the S•O•S coolant analysis tap (4). The coolant

tap is located on the thermostat housing.

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Shown is the hoist and brake hydraulic tank (1) which is equipped with oil level sight gauges.

The oil level should first be checked with cold oil and the engine stopped. The level should

again be checked with warm oil and the engine running.

The lower sight gauge (2) on the hoist and brake hydraulic tank can be used to check the tank level when the hoist cylinders are in the RAISED position. When the hoist cylinders are

lowered, the hydraulic oil level will increase. After the hoist cylinders are lowered, check the

hydraulic tank oil level with the upper sight gauge (3).

Inspect the hoist and brake hydraulic tank breather for plugging. Remove the breather cover (4)

to access the hoist and brake tank breather. The converter and transmission breather (not

shown) is located at the rear of the transmission.

Inspect the condition of the hydraulic tank fill cap vent, which is located in the fill cap (5) at

regular intervals.

When filling the hydraulic tank after an oil change, fill the tank with oil to the FULL COLD

mark on the sight gauge. Turn on the engine manual shutdown switch so the engine will not

start. Crank the engine for approximately 15 seconds. The oil level will decrease as oil fills the

hydraulic system. Add more oil to the tanks to raise the oil level to the FULL COLD mark.

Crank the engine for an additional 15 seconds. Repeat this step as required until the oil level

stabilizes at the FULL COLD mark.

Turn off the engine manual shutdown switch and start the engine. Warm the hydraulic oil. Add

more oil to the tank as required to raise the oil level to the FULL WARM mark.

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Use only Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer.

TDTO TO-4 oil:

- Provides maximum frictional capability required for clutch discs used in the transmission,

torque converter and brakes.

- Increases rimpull because of reduced slippage.

- Increases brake holding capability by reducing brake slippage.

- Controls brake chatter.

- Provides maximum frictional capability required for gears.


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The rear axles are equipped with planetary-type final drives. Rotate the final drive until the

drain plug (1) is at the lowest position. The final drive oil level is checked and filled by

removing the magnetic plug (2). The oil should be level with the bottom of the plug hole. Fill

the rear axle housing with oil before filling the final drives with oil. Allow enough time for the

oil to settle in all of the compartments. This can be as much as 20 minutes during cold

temperatures. The oil is drained by removing the drain plug.

The magnetic inspection plugs should be removed weekly from the final drives and checked for

metal particles. For some conditions, checking the magnetic plugs is the only way to identify a

problem which may exist.

Use FDAO (Final Drive and Axle Oil) or Transmission Drive Train Oil (TDTO) with a

specification of TO-4 or newer. These oils provide:

- Maximum frictional capability required for gears

- Increased lubrication capability for bearings

NOTE: The rear axle is a common sump for the differential and both final drives. If a

final drive or the differential fails, the other final drive components must also be

checked for contamination and then flushed. Failure to completely flush the rear axle

after a failure can cause a repeat failure within a short time.

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Check the differential oil level by removing the magnetic inspection plug (1). The oil should be

level with the bottom of the fill plug opening.

Inspect the rear suspension cylinders for leaks or structural damage. Check the charge

condition of the rear suspension cylinders when the truck is empty and on level ground.

Measure the charge height of the suspension cylinders, and compare the dimension with thedimension that was recorded the last time the cylinders were charged. Recharge the cylinders if

necessary.

Inspect the condition of the rear axle breather (2) at regular intervals. The breather prevents

pressure from building up in the axle housing. Excessive pressure in the axle housing can

cause brake cooling oil to leak through the Duo-Cone seals in the wheel brake assemblies.

NOTE: For more detailed information on servicing the suspension system, refer to the

Special Instruction "Suspension Cylinder Servicing" (Form SEHS9411).

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When work is to be performed while the body is raised (as shown in the top illustration), the

body up retaining pins (1) must be installed through the holes in the body retaining bracket (2)

and the rear frame support (3) to hold the body in the raised position. When the body is in thelowered position (as shown in the bottom illustration), the body up retaining pins are stored

inside a cross-tube (4) in a body support beam directly above the retaining bracket.

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The fuel tank is located on the left side of the truck. The fuel level sight gauge (1) is used to

check the fuel level during the walk around inspection. A fuel level sender is located on the

fuel level sight gauge. The fuel level sender provides input signals to the monitoring system,

which informs the operator of the fuel level.

Open the drain valve below the tank to remove condensation and sediment from the fuel tank.

Inspect the condition of the fuel tank breather (on top of tank) and the fuel fill cap (2) at regular

intervals.

Fuel can be added at the attachment quick service fuel fill connector (3).

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The primary fuel filter (1) is mounted on the left side of the engine. A reusable fuel/water

separator mounts directly to the filter element. Periodically open the valve (2) under the

separator bowl and drain any water into an approved container.

After changing fuel filters, hold the switch (3) upward to activate the electric fuel priming

pump to refill the fuel lines and filters with fuel.

The secondary fuel filter (4) is located next to the primary fuel filter.

A fuel filter bypass switch (5) is located on the filter base. The bypass switch provides an input

signal to the Engine ECM indicating if the filters are restricted.

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While climbing the ladder, make a thorough inspection of the radiator. Be sure that no debris

or dirt is trapped in the radiator cores.

The coolant level on the 770/772 is checked with the jacket water coolant sight gauge (1)

located behind an access door on the left side of the truck. Coolant is added by removing the

radiator cap (2) located next to the sight glass.

The water used in the cooling system is critical for good cooling system performance. Use

distilled or deionized water whenever possible to prevent acids or scale deposits in the cooling

system. Acids and scale deposits result from contaminants that are found in most common

water sources.

Never use water alone. All water is corrosive at engine operating temperatures without coolant

additives. Also, water alone has none of the lubrication properties that are required for water

pump seals.

Cat trucks are filled at the factory with Extended Life Coolant (ELC). If ELC is maintained inthe radiator, it is not necessary to use a supplemental coolant additive. Do not use a

conventional coolant to top-off a system filled with Cat ELC.

An acceptable substitute for ELC is a Cat DEAC (Diesel Engine AntiFreeze/Coolant) or a

commercial heavy-duty coolant/antifreeze that meets ASTM D4985 or ASTM D6210

specifications.

The windshield washer reservoir (3) is located below the coolant sight gauge. Fill the washer

reservoir as necessary.

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The steering system hydraulic tank is located behind the left side of the cab.

Check the steering system oil level at the sight gauge (1), on the side of the tank.

The steering system oil filter (2) cleans the oil before it enters the hydraulic tank.

The steering system uses a pressure compensated piston type pump mounted to the rear of the

engine. Case drain oil from the steering pump returns to the steering tank through a case drain

filter (3).

Before removing the fill cap (4) to add oil to the steering system, depress the pressure release

button (5) on top of the breather to release any pressure from the tank.

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The steering system filter base and the case drain filter base have bypass valves that allow the

steering oil to bypass the filters if they are plugged.

The engine oil level dipstick (6) and the engine oil fill tube (7) are located next to the steering

oil tank. Check the engine oil level with the dipstick and add engine oil at the fill tube.

Caterpillar recommends multigrade Diesel Engine Oil (DEO) with a specification of ECF-1.

API CH-4, CI-4, and CI-4 Plus oils are only acceptable if they meet ECF-1 specifications.

DEO oils with a CG-4 specification are acceptable, but should be limited to 250-hour oil

change intervals. CF and older oils should not be used in Caterpillar diesel engines.

Cat ECF-1 Specification was established by Caterpillar in 2003 and provides excellent soot

dispersion, wear control, and piston deposit control.

The torque converter and transmission dipstick/fill tube (8) is also located next to the steeringtank. The converter and transmission oil can be checked with the oil cold or warm. Observe

the marks on the dipstick.


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The battery disconnect switch (1) is located under a cover (2) above the left front bumper. If

the machine is being parked for an extended period (overnight, etc.) turn off the disconnectswitch and remove the key.

Also located above the left front bumper are the machine lockout switch (3), engine lockout

switch (4), 90 amp alternator circuit breaker (5), 90 amp main circuit breaker (6), and auxiliary

start receptacle (7).

The engine lockout control switch allows the engine to be safely locked out while service is

performed. The engine must be stopped to activate the engine lockout mode. When the engine

lockout mode is activated, the following conditions exist:

- The engine starter is disabled.

- The secondary steering is disabled.

- The prelube function is disabled.

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The following conditions must be met before the engine lockout mode will activate:

- The transmission control must be in the PARK position.

- The engine must be OFF.

When the switch is activated, one of the following results will occur:

- The indicator lamp (8) will illuminate continuously to indicate that the machine is in the

engine lockout mode.

- The indicator lamp will flash to indicate that the engine lockout mode will not activate

until the transmission control is in the PARK position and the engine is OFF.

The machine lockout control switch allows the machine to be safely locked out while service is

performed. When the machine lockout mode is activated, the following conditions exist:

- The engine will start.

- The transmission is disabled.

- The hoist is disabled.

- The steering is disabled.

- The machine lockout mode indicator (9) will illuminate.

NOTE: The lockout mode indicator on the dash panel will illuminate when the engine

lockout control or the machine lockout control is activated.

The batteries (10) are located inside a compartment above the left front bumper. Inspect the

battery connections for corrosion or damage. Keep the battery terminals clean and coated with

petroleum jelly.

Inspect the electrolyte level in each battery cell, except maintenance free batteries. Maintain

the level to the bottom of the fill openings with distilled water.

The engine shutdown switch (11) is located above the right front bumper. The engine will not

start if the manual shutdown switch is ON. If necessary, the switch can be used to stop the

engine from the ground level.


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Shown are the air intake system components.

When servicing the filter elements, clean the precleaner (1) and dust valve (2) using air or water pressure, or detergent wash.

The dust valve is OPEN when the engine is OFF and closes when the engine is running. The

dust valve must be flexible and closed when the engine is running or the precleaner will not

function properly and the air filters will have a shortened life.

Two filter elements are installed in the filter housing. The large element is the primary element

and the small element is the secondary element.

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Air intake system tips:

- The primary element can be cleaned a maximum of six times.

- Never clean the secondary element for reuse. Always replace the secondary element.

- Air filter restriction causes black exhaust smoke and low power.

NOTE: The 770/772 does not have an external air filter restriction indicator. If the air

filter is restricted the turbocharger inlet pressure sensor (3) sends a signal to the Engine

ECM. The ECM sends an input signal to the monitoring system which informs the

operator.


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The remaining 10 Hours or Daily checks are performed in the operator's compartment:

- Brakes: Check operation

- Indicators and gauges: Test operation

- Seat belt: Inspect

- Back-up alarm: Test operation

- Secondary steering: Test operation

The service brakes are checked by depressing the pedal (1) and placing the shift lever in FIRST

FORWARD. Accelerate the engine until the truck moves. The truck must not move below

1200 rpm. This procedure should be repeated to test the secondary brakes by depressing the

secondary brake pedal (2).

The cab air filter (3) is located on the right side of the cab. Clean or replace the cab fresh air

filter when necessary.

NOTE: Refer to the Operation and Maintenance Manual for information on the

remaining tests performed in the cab.

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OPERATOR'S STATION

Shown is a view of the 770/772 operator compartment. The cab for the 770/772 has been

changed to improve operator comfort and ergonomics. The operator seat (1) is centered in the

cab with the trainer's seat (2) positioned to the left.

The hoist control lever (3) is now on the right console next to the transmission control lever (4).

The 770/772 Trucks are equipped with the Messenger Monitoring System (5).

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The Truck Production Management System (TPMS) on the 770/772 is controlled by a TPMS

ECM. There are two sets of TPMS external loading lamps on the truck. One set of lamps is on

the left side of the cab (arrow) and the other set is on the right platform. The lamps are green

and red. The lamps inform the loader operator of the loading progress toward a target payload

weight. The lamps are active only during the loading cycle and are off at all other times.

During loading, the green (continue loading) lamps will be ON until the payload is 95% of the

target weight setting. Then, the red (stop loading) lamp will light. A "last pass" indication can

be programmed into the system. With last pass indication, the TPMS calculates an average

loader pass size and predicts payload weight. If the predicted weight after the NEXT loader

pass will be above 95% of the target weight setting, the red lamps FLASH. The red lamps will

be ON continuously after the last pass (when fully loaded). A minimum of three loader passes

are required for the "last pass" indication option to function correctly. The actual measured

weight of the material in the truck body is displayed on the Messenger display panel.

.

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Located on the left side of the dash are:

- Dash panel light intensity switch (1)

- Head lamp switch (2)

- Hazard switch (3)

- Engine compression brake switch (if equipped) (4)

- ARC switch (5)

- Cigarette lighter (6). The cigarette lighter socket receives a 12-Volt power supply. A

12-Volt power supply is also provided behind the operator's seat.

- Intermittent wiper/washer, turn signal control, and dimmer switch (7).

- Telescopic/tilt steering column adjustment lever (8).

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To the right of the instrument cluster (1) are six rocker switches. The rocker switches are:

- Front brake switch (2). When the front brake switch is in the ON position, the front

brakes will NOT ENGAGE when the operator uses the service brake pedal.

- The optional TCS test switch (3) is used when turning in a tight circle with the engine at

low idle and the transmission in FIRST GEAR. The parking brakes should engage and release repeatedly. The test must be performed while turning in both directions to

complete the test.

- The secondary steering and parking brake release switch (4). Normally, when this switch

is depressed, the steering system receives secondary steering oil and parking brake release

oil flows to the tank. When the brake release diverter (towing) valve spool is shifted, this

switch will also release the parking brakes and provide hoist pilot oil for lowering the

body on trucks with a dead engine.

- The throttle backup/throttle lock switch (5) raises the engine speed to 1300 rpm if the

throttle sensor signal is invalid and allows the desired engine speed to be held at full

throttle without the throttle pedal being depressed.- Optional heated mirror switch (6).

- Air conditioning switch (7).

The Messenger display (8) will be described later in the presentation.

Located below the rocker switches are the key start switch (9), the temperature control

knob (10), and the fan speed switch (11). The manual retarder lever (12) is located on the right

side of the steering column.

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To the right of the operator's seat is a console, which contains the transmission shift lever (1),

and the hoist control lever (2).

The transmission has SEVEN speeds FORWARD and ONE REVERSE.

The top gear limit and body up gear limit are programmable through the Transmission/Chassis

ECM. The top gear limit can be changed from THIRD to SEVENTH. The body up gear limit

can be changed from FIRST to THIRD.

The shift lever lock button (3) must be pushed IN before the shift lever can be moved from "P"

- PARK, "R" - REVERSE, "N" - NEUTRAL, and from "D" - DRIVE to "N" - NEUTRAL.

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The parking brakes are engaged whenever the shift lever is in the "P" - PARK position.

Placement of the shift lever in the "1" - FIRST or "2" - SECOND gear positions will not allow

automatic upshifts or downshifts. This feature will allow the operator to hold the lower gears

when operating in poor under footing.

Placement of the shift lever in the "D" - DRIVE position will enable upshifts and downshifts.

The top gear is selected by use of the momentary buttons in the shifter handle. The top gear

button (4) will shift the top gear selection to the next higher gear through seventh gear. The

bottom gear button (5) will shift the top gear selection to the next lower gear through third gear.

The selected top gear and the actual gear will be displayed on the Messenger display.

The hoist system is electronically controlled. The hoist control lever activates the four

positions of the hoist control valve. The four positions are: RAISE, HOLD, FLOAT, and

LOWER.

A fifth position of the hoist valve is called the SNUB position. The operator does not have

control over the SNUB position. The body up switch controls the SNUB position of the hoist

valve. When the body is lowered, just before the body contacts the frame, the

Transmission/Chassis ECM signals the hoist solenoids to move the hoist valve spool to the

SNUB position. In the SNUB position, the body float speed is reduced to prevent hard contact

of the body with the frame.

The truck should normally be operated with the hoist lever in the FLOAT position. Traveling

with the hoist in the FLOAT position will make sure the weight of the body is on the frame and

body pads and not on the hoist cylinders. The hoist valve will actually be in the SNUB

position.

If the transmission is in REVERSE when the body is being raised, the hoist lever sensor is used

to shift the transmission to NEUTRAL. The transmission will remain in NEUTRAL until:

1. The hoist lever is moved into the HOLD or FLOAT position; and

2. The shift lever has been cycled into and out of NEUTRAL.

The hoist lever is also used to start a new TPMS cycle.

NOTE: If the truck is started with the body raised and the hoist lever in FLOAT, thelever must be moved into HOLD and then FLOAT before the body will lower.


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Located on the floor of the cab are:

- Secondary brake pedal (1): Used to modulate application of the service brakes on the

front wheels and the parking brakes on the rear wheels.

- Service brake pedal (2): The service brake pedal is used to modulate engagement of the

service brakes on all four wheels if the front brake switch in in the ON position.

- Throttle pedal (3): A throttle position sensor is attached to the throttle pedal. The throttle

position sensor provides the throttle position input signals to the Engine ECM.

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Located to the right of the operator's seat is the fuse panel (1), the Cat ET service port (2), the

TMPS service port (3), a 12V power receptacle (4), the 15 amp heater/air conditioner fan circuit

breaker (5), and the 15 amp Engine ECM circuit breaker (6).

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MONITORING SYSTEM

The monitoring system on the 770/772 trucks monitors various machine systems and conveys

the machine status, communicated from the other ECMs to the operator. The monitoring

system includes an instrument cluster and a Messenger display module.

The instrument cluster is a cab display that shows the operator the status of various machine

parameters and alerts the operator of specific machine conditions. The instrument cluster is

operated by the Messenger display via the Controller Area Network (CAN) Data Link.

The Messenger display is an LCD module with four operator actuated pushbuttons which allowthe operator to access menus to display machine status along with diagnostics, events, and

TPMS data. The Messenger can also be used to set desired values for various machine

functions.

The Truck Payload Monitoring System (TPMS) is an optional system that can be installed on

the trucks to monitor and record production data such as payloads and cycle times. The TPMS

requires a separate communication port for programming, downloading, and viewing the

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Shown is the Instrument Cluster located in the center of the front dash panel. The Instrument

Cluster includes 18 dash indicators, five analog gauges, and an LCD digital display (1). The

LCD display window in the lower center of the dash includes the truck speed, the gear, and the

direction on the top of the display and the service hour meter on the bottom of the display.

The five parameters monitored by the analog gauges are the:

- Brake oil temperature (2)

- Engine coolant temperature (3)

- Engine speed (4)

- Torque converter oil temperature (5)

- Fuel level (6)

Problems from the machine systems are classified into four warning categories (1, 2, 2S, and 3)

similar to other Caterpillar monitoring systems.

During the normal operation mode and the menu mode, the Messenger display may be

interrupted by a warning message. Warning messages are displayed when important

instructions or information need to be displayed.

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This illustration shows the gauges and indicators on the instrument cluster.


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n/minX100 R

Brake SystemCheck

Park Brake

Engaged

Power TrainSystem Check

Act ionLamp

Check Engine

EngineRPM

ElectricalSystem

Body Up

Transmission in Reverse

Machine Lockout Active

High Beam

Retarder Engaged

MachineImmobilizer

Traction ControlSystem EngagedPrimary Steering

Loss

Secondary SteeringEngaged

TransmissionOil Temperature

Gauge

Engine CoolantTemperature Gauge

Throttle Lock

Left Turn SignalRight Turn Signal

Brake OilTemperature Gauge

Fuel Level Gauge

LCD DisplayWindow

Truck Speed Act ive Gear and Direction

Service Hour Meter

INSTRUMENT CLUSTER

mphkm/h

kPa psi

n/min

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Messenger Display Module

The standard Messenger display module (1) is located in the right side of the front dash. The

purpose of the Messenger is to display relevant machine information to the operator or service

personnel. The Messenger display is used in conjunction with the instrument cluster to act as

the monitoring system for the machine.

The Messenger has a menu structure that allows the user to access the desired machine

information. The default screen will display under normal machine operating conditions

without any intervention from the operator or service personnel.

This illustration shows the default screen of the Messenger module that shows the shift lever

and the gear position. The default screen is displayed at machine start-up and until the operator

or the technician navigates to another screen.

The Messenger consists of the display and four navigation buttons that are used to navigate

through the menu structure. The button functions from left to right are as follows:

Back (2): Used to navigate to the previous screen that was accessed in the Messenger.

Left/Up (3): Allows the user to scroll left or up. Scroll direction is dependent on the

specific data that is being displayed on the screen.

Right/Down (4): Allows the user to scroll right or down. Scroll direction is dependent on

the specific data that is being displayed on the screen.

OK (5): Acts as a confirmation function for the Messenger.

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Shown is the default screen for the Messenger.

Message Bar: In the default mode the message bar displays the Fuel Economy Mode status

and payload information if TPMS is installed.

Transmission Gear Range: The transmission gear range displays the full gear range of the

transmission. In this illustration the 770/772 transmission ranges from Park to 7th gear.

Selectable Transmission Range: The selectable transmission range displays the transmission

gear values that the operator can select. The full range of transmission gears can be limited

using Cat ET. In this illustration the transmission top gear has been limited to 5th gear asshown by the rectangle.

Drive Gear Selection Indicator: The drive gear selection indicator displays the desired

transmission gear when the shift lever is in the DRIVE position. The desired transmission gear

(underlined) is selected with the shift lever in DRIVE using the drive gear scroll up or down

switches.


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Shift Lever Indicator: The shift lever indicator displays the gear that the transmission is

being limited to. When the transmission is not being limited, this indicator will display the

shift lever position (highlighted). When the transmission is being limited, such as 2nd gear

limit with the body up, this indicator will display the gear value to which the transmission is

being limited.


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The Messenger Menu Screen is divided into three sections. The top section identifies the name

of the current menu. If the current name is split by a colon ":" then this indicates that the name

after the colon ":" is the current menu and the name before the colon ":" is the parent menu of

the current menu. The center section displays the current menu option that can be selected by

pressing the OK button. The arrows at the left of the screen indicate whether you can scroll to

the next screen to see further menu options.

There are a total of five main menus that are available for navigation. Only one menu can be

displayed at a time. The menus are accessed from the default menu by pressing the back arrow

button. The five menus are:

- Performance

- Totals

- Settings

- Service

- Service mode


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This illustration of a performance screen submenu shows the engine coolant temperature and

shift lever position.

A typical Messenger information screen normally displays the information in pairs. The

headers at the top of the screen identify the information. The current values are displayed

below the headers. The arrows at the left of the screen indicate whether you can scroll to thenext screen to see additional information.

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The Performance menu allows the operator or technician to view two pages of information.

These pages of information monitor vital machine system data during machine operation. This

information can only be viewed. The Performance menu uses two screens to show the real time

status of the information listed above on the right side of the illustration.


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The Totals main menu allows the operator or the technician to access information about the

machine systems. The totals data can be used to determine when scheduled maintenance is

required.

The Totals menu shows accumulated values and includes two submenus. The two submenus

are Payload and Machine.

The Payload and Machine submenus display the information listed on the right side of the

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Parameters are normally adjusted for specific operating conditions, operator preferences, and

machine operating efficiency. The machine setup affects the parameters that are displayed. The

attachments that are on the machine determine the software that is contained in the ECMs.

Messenger looks at the software versions to determine the parameters that will be displayed and

the parameters that will be variable.

NOTE: Cat ET can also be used to access the parameters.

The Settings menu allows the user to adjust the parameters for the following submenus:

- Messenger Display

- Machine Identification

- Transmission Operation

- Brake Operation

- Payload Operation

- Engine Operation

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The Messenger Display parameters relate to the operator’s preferences for the Messenger

display. The following parameters may be adjusted:

- Language: Six standard languages (other languages available).

- Units: Metric or English.

- Contrast: Screen contrast.

- Headlights On: Screen brightness with headlights ON.

- Headlights Off: Screen brightness with headlights OFF.

The Machine settings allow the user to set the machine serial number. The following

parameters may be adjusted:

- Product ID: Allows the user to set the machine serial number (password protected).

- Equipment ID: Allows the name of the truck to be changed (password protected).

The Transmission setting allows the following parameters to be adjusted:

- Top Gear Limit: Allows the user to set the highest gear performance level.

- Body Up Gear Limit: Adjusts the gear limit during truck operation when the body is

raised.

- Machine Speed Limit: Sets the highest truck speed.

- Fuel Economy Mode: Allows the fuel usage to be changed.

- Machine Overload Speed Limit: Limits transmission gear and engine speed when

excessive payloads are detected (if machine is equipped with TPMS).

The Brake setting allows the user to set the desired ARC speed and is password protected.

The Payload menu allows the configuration of the Payload settings and is password protected.

The Payload settings include the following:

- Target Payload: Read and program the truck target payload.

- Overload Limit: Read and program the percent overload.- Green TPMS Lamp: Read and program the installation of the green TPMS lamp.

- Red TPMS Lamp: Read and program the installation of the red TPMS lamp.

- Last Pass Enabled: Read and program the installation of the Last Pass indicator. The

Last Pass indicator informs the shovel operator of the last load before the payload is over

the rated load.

The Engine setting allows the user to change the ether solenoid configuration to "No Ether

Solenoid Installed" or "Continuous Flow" and is password protected.


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The Service menu allows the technician to access the machine parameters. The technician may

also make selections for viewing or clearing logged events or codes.

The Service menu will allow the technician to view data for the following systems: brake,

steering, implement, and power train. The status of electronic components in the machine’s

major systems can also be viewed. The Service menu option is displayed by selecting Servicefrom the Main Menu. Press the Left/Up arrow button or the Right/Down arrow button until

Service is displayed. Then press the OK button. The Service menu contains the following six

submenus:

- Diagnostic Events: Displays a complete list of all active and inactive event codes and

diagnostic codes.

- System Parameters: Allows the technician to view the status of system components.

- Calibrations: Allows the technician to perform a payload calibration. The payload

system must be calibrated if new TPMS software is installed or the machine serial

number is reprogrammed.

- System Tests: Allows the user to perform a transmission stall test or a system self test on

the machine.

- Systems Information: Allows the user to display information on all of the ECMs installed

on the machine, such as ECM Part Number, etc.

- Tattletale: The Messenger display module records the extreme value for each condition

of the machine that is monitored.

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These illustrations show the information available within the Diagnostic Events menu.

From the Service menu, use the appropriate arrow button to highlight the Diagnostic Events

option and press the OK button to access the Diagnostic Events. Select the View Diagnostics

display by pressing the OK button. The View Diagnostics option will display a complete list of

codes (bottom left illustration). Each line on the list will show the following information:

- SRC (Source ID)

- CODE

- OCC (Number of occurrences of the event or code)

- ACT (if the code is active or inactive).

Use the appropriate arrow button to highlight a diagnostic code or an event code on the list.

Press the OK button to display the codes Detailed View (bottom right illustration). The

Detailed View will display a text message that shows the following information: the reporting

ECM, the failed component code, and the explanation of the event.

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The technician can clear logged codes one at a time. Active codes are indicated with a mark

under the "ACT" column. Active codes cannot be cleared until the faults have been corrected.

To clear a code, access the Detailed View of the code, press the OK button and follow the

prompts and directions.

NOTE: Only Level I and Level II codes may be cleared with Messenger. When a code

is cleared from Messenger, the memory from the reporting ECM is cleared. The code is

not cleared from the Messenger ECM. Once the code has been cleared from the

reporting ECM, Messenger will update the code list. Messenger is an interface between

the technician and the machine ECMs.


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The Service Mode Password menu is used to enter the Service mode. The Service Mode

Password protects certain features from access by the operator. Features that need to be

protected from the operator can be enabled or disabled with a password.

NOTE: For more information on the Messenger Monitoring System, refer to the

770/772/773F/775F/777F Off-highway Truck Monitoring Systems Operation,Troubleshooting, Testing, and Adjusting Service Manual module (RENR8244).

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ENGINE

Shown is the C15 engine with ACERT™ Technology used in the 770 Off-highway Truck.

The engine performance specifications for the 770 Trucks are:

- Serial No. Prefix: LHX

- Performance Spec: 0K5752

- Gross Power: 344 kW (461 hp)

- Full Load rpm: 1800

- High Idle rpm: 2200 ± 10

- Low Idle rpm: 650 ± 10

- Stall Speed rpm: 1585 ± 65

- Boost at Full Load rpm: 145 - 193 kPa (21 - 28 psi)

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The engine performance specifications for the 772 trucks are:

- Serial No. Prefix: RHX

- Performance Spec: 0K5749

- Gross Power: 391 kW (524 hp)- Full Load rpm: 1800

- High Idle rpm: 2200 ± 10

- Low Idle rpm: 650 ± 10

- Stall Speed rpm: 1842 ± 65

- Boost at Full Load rpm: 152 - 207 kPa (22 - 30 psi)

This six cylinder engine uses a turbocharger, Air to Air AfterCooler (ATAAC) and Mechanical

Electronic Unit Injection (MEUI) for power, for reliability, and for fuel economy. The C15 and

C18 engines are compliant with U.S. EPA Tier 3 and European Union Stage II emissionsregulations.


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Engine Electronic Control System

Shown is the electronic control system component diagram for the C15/C18 engines used in the

770/772 Trucks. Fuel injection is controlled by the Engine Electronic Control Module (ECM).

Many electronic signals are sent to the Engine ECM by sensors, switches, and senders. The

Engine ECM analyzes these signals and sends signals to various output components. Output

components can be relays, lamps, other controls, or solenoids.

For example, based on the various input signals, the Engine ECM determines when and for how

long to energize the injector solenoids. When the injector solenoids are energized determinesthe timing of the engine. How long the solenoids are energized determines the engine speed.


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Fuel injection and other systems are controlled by the Engine ECM (arrow) located on the left

side of the engine. Other systems controlled by the Engine ECM include:

- Ether injection

- Engine start function

The Engine ECM has 120-pin connector and 70-pin connector. The connectors are identified as

"J1" and "J2." Be sure 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 the

performance of the engine. These changes can be performed by using the WinFlash program in

Cat ET. If using the WinFlash program, a "flash" file must be obtained from Caterpillar and

uploaded to the ECM.

A 2-pin timing calibration connector is located next to the ECM. If the engine requires timing

calibration, a timing calibration sensor (magnetic pickup) is installed in the flywheel housing

and connected to the timing calibration connector.

Timing calibration is performed automatically with Cat ET for both speed/timing sensors.

Timing calibration is performed to avoid instability and ensures that no backlash is present in

the timing gears during the calibration process.

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Timing calibration improves fuel injection accuracy by correcting for any slight tolerances

between the crankshaft, timing gears, and timing wheel.

Timing calibration is normally performed after the following procedures:

- ECM replacement

- Speed/timing sensor replacement

- Timing wheel replacement


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The intake manifold pressure sensor (1) is located behind the secondary fuel filter (2). The

intake manifold pressure (boost) sensor sends an input signal to the ECM. The ECM compares

the value of the boost sensor with the value of the atmospheric pressure sensor and calculates

boost pressure.

One function of the boost sensor is to enable the air/fuel ratio control, which reduces smoke and emissions, and maintains engine response during acceleration. The system utilizes boost

pressure, atmospheric pressure, and engine speed to control the air/fuel ratio. Engine fuel

delivery is limited according to boost pressure and engine speed. A failure of the turbocharger

outlet pressure sensor can cause the engine to derate as much as 60% when the ECM defaults to

a zero boost condition.

The primary fuel filter/water separator (3) is also visible in this illustration.

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The intake manifold air temperature sensor (1) is located on the left side of the engine in the

head near the air intake. The air temperature sensor is used for derating the engine at high

temperature, for engine shutdown at high temperature, and for use by the monitoring system.

The engine oil pressure sensor (2) is located in an adapter on the left side of the engine. Engine

oil pressure varies with engine speed. If the engine oil pressure is less than specification, the

Engine ECM will log an event that requires a factory password to clear.

The atmospheric pressure sensor (3) is located in an adapter on the left side of the engine next

to the engine oil pressure sensor. The Engine ECM uses the atmospheric pressure sensor as a

reference for calculating boost, air filter restriction, and derating the engine at high altitudes.

All pressure sensors in the system measure absolute pressure, and require the atmospheric

sensor to calculate gauge pressure.

All the pressure sensor output signals are matched to the atmospheric pressure sensor output

signal during calibration. Calibration can be accomplished using Cat ET or by turning on the

key start switch without starting the engine for five seconds.

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The engine coolant temperature sensor (arrow) is located in the front right of the engine in the

thermostat housing. The coolant temperature sensor is used by the Engine ECM to control

various functions. The following systems or circuits use the coolant temperature sensor input

signal to the Engine ECM:

- The monitoring system coolant temperature gauge- Cold mode operation

- Automatic ether injection

If the jacket water cooling system temperature increases above 107°C (226°F), the Engine

ECM will log an event that requires a factory password to clear.

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The cam speed/timing sensor (1) is located on the left side of the engine in the back side of the

timing gear housing near the secondary fuel filter (2). The cam speed/timing sensor is used as

a back-up for the crank speed/timing sensor. If the crank speed/timing sensor fails, the camspeed/timing sensor allows for continuous operation.

The crank engine speed/timing sensor (3) is located on the lower left corner of the engine near

the air conditioning compressor (4). The crank speed/timing sensor measures engine speed and

timing for control of the timing and delivery of fuel to each of the engine's cylinders. Sensing

engine speed allows engine speed governing, fuel limiting, and fuel injection timing.

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The engine will start and run when only one sensor signal is present from either the crank or

cam sensor. During engine operation, if both speed/timing sensors fail, the Engine ECM will

stop fuel injection and the engine will shut down. During start-up, the loss of both sensors will

prevent the engine from starting.

If the engine is running and the signal from the crank speed/timing sensor is lost, a slight

change in engine performance will be noticed when the Engine ECM performs the changeover

to the cam speed/timing sensor. If the signal from the crank speed/timing sensor is not present

during start-up, the engine will start normally.

Loss of the cam speed/timing sensor during engine operation will not result in any noticeablechange in engine performance. However, if the signal from the cam speed/timing sensor is not

present during start up, the engine may require a slightly longer period of time to start and may

run rough for a few seconds until the ECM determines the proper firing order by using only the

crank engine speed/timing sensor.


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Located behind the right pedal, the throttle position sensor (arrow) provides the desired throttle

position to the Engine ECM. If the Engine ECM detects a fault in the throttle position sensor,

the throttle back-up switch in the cab can be used to increase the engine speed to 1300 rpm.

The throttle position sensor receives a regulated 8.0 ± 0.5 Volts from the Engine ECM. The

throttle position sensor output signal is a Pulse Width Modulated (PWM) signal that varies withthrottle position and is expressed as a percentage between 0 and 100%.

To check the output signal of the throttle position sensor, connect a multimeter between Pins B

and C of the throttle position sensor connector. Set the meter to read "Duty Cycle." The duty

cycle output of the throttle position sensor should be:

- Low Idle: 16 ± 6%

- High Idle: 85 ± 4%

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The pre-lubrication (QuickEvac) pump (1) is located on the end of the secondary steering/brake

release pump and motor assembly (2). The pump and motor assembly is located on the left

frame rail next to the engine.

The engine oil pre-lubrication QuickEvac pump is controlled by the Transmission/Chassis

ECM. The Transmission/Chassis ECM energizes the pre-lubrication pump relay located behind the cab. The relay behind the cab then energizes the prelube relay.

The QuickEvac mode is used to allow the technician to quickly evacuate the oil for an oil

change. The QuickEvac mode can only be performed when the engine lockout is activated.

Engine starting and pre-lubrication functions are also inhibited when the engine lockout is

activated.

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If the truck is equipped with an ether start system, the Engine ECM will automatically inject

ether from the ether valve (arrow) and ether cylinder during cranking. The amount of automatic

ether injection depends on the jacket water coolant temperature. The Engine ECM sends a duty

cycle signal to the ether injection relay. The maximum duty cycle is 50%. A 50% duty cycle

will pulse the ether relay ON three seconds and OFF three seconds. The maximum ether

delivery is ten 3-second shots per minute. Each shot delivers 6 ml (0.2 oz) of ether.

The Engine ECM will energize the ether injection relay only if:

- Engine intake manifold air temperature is below a certain temperature.

- Engine coolant temperature is below a certain temperature.

Cat ET can be connected to the machine to turn the ether injection system ON or OFF.

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Engine Derates

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 a

Level 1 Warning.

When the temperature of the coolant exceeds 111° C (231° F), the Engine ECM will initiate a

Level 2 Warning. At 111° C (231° F) the Engine ECM will initiate a 25% derate. Refer to the

illustration 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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An engine derate can occur due to a estimated (virtual) high exhaust gas temperature. The

Engine ECM monitors barometric pressure, intake manifold temperature, and engine speed to

estimate 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. The

Engine ECM determines a maximum fuel delivery percentage to maintain safe maximum power

output under load. This calculation is new to the off-road Tier III engines and is used in place

of 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 most

critical derate condition input will be used to adjust fuel system delivery limiting engine power

to a safe level for the conditions in which the product is being operated, thereby preventing

elevated exhaust temperatures.


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Engine ECM

Barometric Pressure

Inlet Manifold Temperature

Engine Speed

Engine DeratePercentage

Highest DeratePrioritySelector

Other EngineDerate

Conditions

VIRTUAL EXHAUST TEMPERATURE DERATE

Fuel InjectionCalibration

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The virtual exhaust temperature derate will log a 194 event code. The derate will enable a

Level 1 Warning and eventually a Level 2 Warning. The level of the warning will depend on

the conditions that are sent to the Engine ECM.

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

- No CID 168 01 FMI (low battery voltage to the Engine ECM) is 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 temp derate must be the highest derate.

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

This derate is triggered by the information inferred by the Engine ECM, rather than an

individual sensor as with the previous single derate strategies. If you think this derate is

possibly being imposed incorrectly check for event codes on high intake manifold temperature

and correct those first. Also, make sure the aftercooler is unobstructed. For additional

information about troubleshooting, refer to the troubleshooting for the particular engine that is

being serviced.


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

the low oil pressure derate.

When the oil pressure is below the blue line 154 kPa @ 1600 rpm (22 psi @ 1600 rpm), the

Engine ECM will enable the low oil pressure Level 1 Warning. Change machine operation 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), the

Engine ECM will enable the low oil pressure Level 3 Warning. The operator should

immediately 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 Engine

ECM will initiate a low engine oil pressure Level 1 Warning.


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This illustration shows the graph for the warning and derates map for the fuel temperature.

When the fuel temperature exceeds 90° C (194° F), the Engine ECM will activate a Level 1

Warning. Also, the graph shows, as the fuel temperature increases to 91.0° C (196° F) a Level

2 Warning will be initiated by the Engine ECM. At the same time, the engine will derate to

12.5%. If the fuel temperature 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%.

Excessive fuel temperature will cause injector wear.


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When the differential pressure switch recognizes a fuel pressure of 103 kPa (15 psi) for 3

minutes, the Engine ECM will initiate a Level 1 Warning.

When the differential pressure switch recognizes 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 of 17.5%.

The total derate will be 35%.

The high fuel filter restriction derate will be disabled when the fuel temperature is below 30° C

(86 ° F).


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Cooling System

The jacket water cooling system on the 770/772 uses a Next Generation Modular Radiator

(NGMR). The NGMR (1) is a single-pass flow design, replacing the two-pass flow folded core

system. The coolant enters at the top left and flows out at the bottom right, similar to an

automotive design. Being modular, individual cores may be removed for service while theradiator remains in place.

The ATAAC (2) is located in front of the radiator. Intake air is cooled after being compressed

by the turbocharger before being routed to the engine combustion chamber. Also visible in this

illustration is the air conditioning condenser (3).

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1

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Jacket water coolant flows from the water pump through the engine oil cooler, through the

brake oil cooler, and the transmission and torque converter oil cooler to both sides of the engine

cylinder block. Coolant flows through the engine block to the cylinder heads. From the

cylinder heads, the coolant flows to the temperature regulator and, based on coolant

temperature, either flows to the radiator (if hot) or through the bypass tube to the water pump

(if cold) to recirculate until the engine reaches operating temperature.

The thermostat is located in the thermostat housing.

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These illustrations show the components in the cooling system:

- Water pump (1)

- Engine oil cooler (2)

- Transmission and torque converter cooler (3)

- Brake oil cooler (4)

- Thermostat housing (5)

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1

2

3

5

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The 770/772 trucks are now equipped with a hydraulic fan. The previous machines had belt

driven fans. This block diagram shows the major components of the fan system.

Oil from the brake/fan pump flows to the accumulator charging valve. The accumulator

charging valve directs the pump flow to the brake accumulators and to the fan speed control

valve.

The fan speed control valve controls the fan speed. The Transmission/Chassis ECM determines

the fan speed and sends a signal to the solenoid in the fan speed control valve. The solenoid

valve then directs the appropriate amount of pump flow to the fan motor. Return oil from the

fan motor is directed to the fan speed solenoid valve and to the brake oil cooler.

If the fan overspeeds, return oil is directed through a check valve to the supply side of the fan

motor to prevent cavitation.

The Transmission/Chassis ECM controls the fan speed based on information from the machine

sensors.


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This illustration shows the fan motor (1) and fan speed control valve (2). The control valve is

located on the inside of the front pedestal below the cab brake manifold (3).

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The 770/772 trucks can be equipped with a body heat diverter option that directs heat from the

exhaust to the truck bed. This illustration shows the fan hydraulic circuit with the body heat

diverter option.

Return oil from the fan motor flows to a relief valve and to the diverter box solenoid valve in

the fan speed and diverter box control valve. The relief valve maintains a pressure in the return

side of the fan circuit. The diverter box solenoid directs the pressurized return oil to the

diverter box actuator cylinder, which opens and closes a door that blocks or allows exhaust air

into the truck bed.


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This illustration shows the location of the relief valve (1), the fan speed solenoid (2), and the

diverter box solenoid valve (3) on the fan speed control valve (4).

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3

4

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The diverter box actuator cylinder (arrow) is attached to the exhaust on the right side of the

machine.

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Lubrication System

The engine oil pump draws oil from the oil pan through a screen.

Oil flows from the pump through an engine oil cooler bypass valve to the engine oil cooler.

The bypass valve for the engine oil cooler permits oil flow to the system during cold starts

when the oil is thick or if the cooler is plugged.

Oil flows from the engine oil cooler to the oil filter. The oil flows through the filter and enters

the engine cylinder block to clean, cool, and lubricate the internal components and the

turbochargers.


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Fuel System

The fuel tank is located on the left side of the truck. Fuel is pulled from the tank through the

primary fuel filter by the fuel transfer pump.

Priming is now done electrically using a switch (arrow) located above the primary fuel filter. Areusable fuel/water separator mounts directly to the bottom of the fuel filter.

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The fuel transfer pump (1) is located at the bottom of the timing gear housing on the left side of

the engine. The fuel transfer pump contains a bypass valve to protect the fuel system

components from excessive pressure. The bypass valve setting is higher than the setting of the

fuel pressure regulator. Fuel flows from the transfer pump to the secondary fuel filter (2).

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The differential fuel pressure switch (1) is located in the top of the secondary fuel filter housing

on the left side of the engine. This switch will indicate a restriction in the fuel

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