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Scania Retarder

Function description

1 0 : 2

2 8 8

1 712 020

10:05-07Issue 2 en

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Contents

2 Scania CV AB 1999, Sweden 10:05-07 en

Contents

Electrical System General............................................................ 3

The design of the system ................................ 4

Interaction with other systems ........................................................................ 7Retarder CAN ................................................. 9

Brake sensor functions Brake pedal sensor........................................ 11Lever sensor.................................................. 13

System functions Brake lamp.................................................... 14Limiting at high temperatures....................... 14

ABS/EBS communication, general .............. 15

EDC communication, general....................... 17

Exhaust brake ............................................... 18

MBP (engine brake program) output............ 21

Warming up the driver andpassenger compartments............................... 22

Configuration General.......................................................... 23

Configuration codes...................................... 24Configuration, explanations.......................... 27

Control unit as a part..................................... 29

Control unit connections ...................................................................... 31

Warning system General.......................................................... 35Warning lamp, fault indication ..................... 37

Resetting the warning system ....................... 38

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1050f15b.mkr Scania CV AB 1999, Sweden 3

Electricalsystem

Electrical system

General

The auxiliary brake control unit ismicroprocessor based.

The control unit and its program are thesame for all versions. How the control unitcarries out its tasks depends on theconfiguration. This is described under theheading Configuration.

The control unit is equipped with anintegrated warning system, see Main group10 Scania Retarder, Function descriptionunder the heading Warning system.

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4 Scania CV AB 1999, Sweden 1050f15b.mkr

The design of the system

The illustration is general and applies to both trucks and buses. Vehicles with a lower level ofequipment are covered where appropriate.

r/min

1520

25

30

10

5

0

EDC km/h

Opticruise

1 0

_ 2 1 0 4

12

1 2 3 4

5

6

7 8 9

10

11

13

14

15

16

17

18

19

20

ABS/EBS

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The design of the system

1 The clutch pedal switch is used to enablethe driver to increase throttle whenchanging down without interruptingdownhill speed control 1 or braking usingthe hand lever.

Note: Actuating the accelerator pedalinterrupts retarder braking when the clutchpedal is in the released position.

2 The brake pedal sensor is used to provideretarder braking using the brake pedal 2 andto automatically activate downhill speedcontrol 3.

3 The accelerator pedal sensor sends a signalto the control unit to interrupt downhillspeed control or retarder braking that hasbeen requested with the lever. If, on theother hand, the clutch pedal is in depressedposition, retarder braking continues.

4 The AUT switch is used to make it possiblefor the retarder and downhill speed controlto be activated automatically using thebrake pedal. It must also be possible for the

driver to shut down all retarder activationfrom the brake pedal e.g. on slipperysurfaces.

5 The hand lever has six positions. The fivebrake positions each give a fixed brakingtorque: 500, 1000, 1500, 2000, 3000 Nm.In the max. position, the exhaust brake isalso activated, according to the conditionsunder the heading System functions,Exhaust brake.

6 The switch on the top of the lever is formanual activation of downhill speedcontrol.

7 Warning lamp to warn of faults in theauxiliary brake system or its adjoiningsystems and circuits.

1.Downhill speed control requires the vehicle to be equipped

with ABS/EBS.2.Brake pedal control requires the vehicle to be equipped withABS/EBS.3.Optional equipment on trucks only.

8 Main exhaust brake switch. For trucks after9911, this switch is only fitted to vehicleswith automatic exhaust brake (EXB).

9 Diagnostic socket for PC.

10 PC with SD trouble shooting program.

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11 The exhaust brake 1 is not controlled by thedriver but by the control unit.

12 Dual temperature sensors at the outlet fromthe retarder oil cooler. The temperatureforms the basis of the decision by thecontrol unit for any temporary decrease inbraking power.

13 The proportional valve controls braketorque to the requested level at differentroad speeds. As road speed decreases, theretarder requires higher and higher oilpressure to be able to brake with therequested torque. The proportional valvecontrols this and so enables the retarder tobrake at speeds down to approx. 20 km/h.

14 The stop light illuminates when theauxiliary brake is applied. This is illegal incertain markets. This feature can bedeactivated by removal of relay R8.

15 The auxiliary brake communicates with theEDC system to ensure that the two systemswill not interfere with each other'soperation. Braking disengages the cruisecontrol of the EDC and depressing theaccelerator disengages retarder braking.

16 The auxiliary brake receives informationfrom the ABS/EBS system so that it candisengage retarder braking at short notice.Signals from the ABS/EBS system aboutABS control interrupt retarder brakingwithin 0.2 seconds. Retarder braking viathe brake pedal as well as all downhillspeed control are disengaged by any faultin the ABS-system.

17 The engine speed gives the control unitcontinuous information about availablecooling capacity. The control unit candemand a temporary decrease in retarderpower and so prevent overheating in thecooling system.

18 The auxiliary brake receives road speeddata from the Opticruise, CS 2 or thegearbox over-revving protection. Seeparagraph 13.

1.Some buses are not equipped with exhaust braking.2.Optional equipment on buses only.

19 The auxiliary brake orders the Opticruisesystem to switch to the engine brakeprogram if engine speed and, accordingly,cooling capacity is insufficient.

20 The diagnostics lamp and diagnosticsswitch are concealed under a cover in theinstrument panel.

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Interaction with other systems

The block diagram at the end of thisdescription shows which other systems areconnected to the Scania auxiliary brake systemand in which directions information isexchanged.

Fault codes are a part of this exchange ofinformation and therefore, for example, the CSsystem fault codes will be shown under theauxiliary brake system.

The illustration applies to both trucks and busesand covers all appropriate optional equipment.

The auxiliary brake is connected to thealternator's tachograph signal, W+. Thismeans that the control unit can determinethe speed of rotation of the coolant pumpand thus also know the volume of coolantflow at any moment.

Retarder braking generates a great deal ofheat and this must be dissipated by thevehicle's ordinary cooling system. Brakingpower may reach approx. 540 hpcontinuously and up to 880 hp for shortperiods.

Do not confuse the alternator signal W+ withthe EDC systems PWM signal. The PWMsignal gives the throttle position and notcoolant flow.

The auxiliary brake is connected to theEDC system to ensure that the two systemswill not interfere with each other'soperation.

The EDC must know if the driver isbraking using the auxiliary brake, and thendisengage the cruise control of the EDC.

Moreover, the auxiliary brake must bedisengaged as soon as the driveraccelerates, irrespective of whether he isaccelerating with the pedal or with thecruise control of the EDC.

The auxiliary brake is connected to theABS/EBS system so that it will notinterfere with ABS control.

The auxiliary brake brakes hard, but onlyon the driven wheels. For this reason the

ABS/EBS system disengages the auxiliarybrake during ABS control. Afterwards,when ABS control has finished, theauxiliary brake can function as normal.

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The auxiliary brake is connected to theOpticruise, CS or the normal overrevvingprotection of the gearbox, so that thecontrol unit can obtain data on the vehicleroad speed.

The working parts of the auxiliary brakei.e. the retarder and the exhaust brake, havedifferent effects at different road speeds.On the basis of the road speed, the controlunit can decide how to achieve optimumbraking and then activate the retarder, theexhaust brake or both.

The auxiliary brake is connected to theOpticruise to enable it to request theactivation of the engine brake program.

If the downhill speed control regulator inthe auxiliary brake control unit perceivesthat it is not able to maintain speed, it caneven order the Opticruise to change downas soon as possible.

Over long periods, it can be said that theauxiliary brake takes precedent over theOpticruise. In the short term the opposite isthe case. For example, if the auxiliarybrake has requested braking of the vehicle

by means of the exhaust brake, theOpticruise system will still be able tocontrol the exhaust brake during its gear-changes. When each gear-change iscomplete, the exhaust brake will again beused for braking the vehicle.

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Retarder CAN

From 9911 the retarder control unit uses CANcommunication to communicate with EBScontrol units. Applies to trucks only. Thecommunication cables CAN LOW and CANHIGH are connected to pins 39 and 40 on theretarder control unit.

CAN communication

CAN is an abbreviation of Controller AreaNetwork. CAN communication is used toreduce the number of cables in the vehicle andat the same time increase reliability. CANcommunication is serial data communicationand can be compared to communication

between computers in a network.Every control unit that communicates usingCAN is connected to the CAN LOW and CANHIGH cables. Through these cables, eachcontrol unit continuously sends and receivesCAN messages to and from other control units.Which CAN message the control unit sends orlistens for depends on the configuration of thecontrol unit.

As a mechanic, it is important to remember that

individual CAN signals cannot be checkedusing a Multimeter.

Retarder CAN and EBS

EBS version 2.2 is introduced at the same timeas Retarder CAN. These systems communicateusing CAN if the configuration Brake torquevia CAN is selected for the retarder in ScaniaProgrammer.

If the retarder has this configuration, the EBSsystem will have priority over the retarder andvia CAN signals, decide how much the retardershould brake when the brake pedal isdepressed. The retarder then decides when andhow much the exhaust brake should beactivated for the requested brake torque.

CAN signals sent from EBS to the retarder areas follows:

Requested brake torque

ABS control

EBS/ABS fault

CAN messages sent from the retarder to EBSare as follows:

Regulated brake torque

Configuration, max. retarder torque

Retarder CAN and EDC

For certain engine types with EDC,communication with the retarder occurs via thetwo CAN cables. Applies to trucks from 0005only.

The retarder communicates with the EDC viaCAN, if the configuration "Engine fan control"

is selected in Scania Programmer.

When "Engine fan control" is selected, theretarder control unit will send CAN messageswith the desired engagement level of the enginefan to the EDC control unit. The engagementlevel depends on the coolant temperature.

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Vehicles equipped with a coordinator

The EDC control unit sends informationconcerning the current fuel volume and thecurrent engine speed via CAN bus to thecoordinator, COO. The coordinator converts

the information and generates a PWM signalfor current fuel volume and a W signal for theengine speed, these signals are sent to theretarder control unit, RET. The retarder controlunit receives several other input signals, suchas from the temperature sensor. When theretarder control unit senses too high a coolanttemperature, it can send a signal on the CANbus to the EDC control unit with a request forfan control. The EDC control unit then decidesthe engagement level.

On vehicles equipped with a coordinator, it isimportant that the retarder control unit isalways programmed as if the vehicle had a6 pole alternator with an alternator frequencyof 172Hz. This is because the W signal that isgenerated by the coordinator is equivalent tothe signal from a 6 pole alternator.

Scania integrated auxiliary brake system

A Scania integrated auxiliary brake system B EDC systemC Opticruise system

D CS system or overrevving protection E ABS, ABS/TC or EBS system up to andincluding version 2.1F EBS system from version 2.2 onwardsG Tachograph signal from the alternator Signal routes between the auxiliary brakecontrol unit and other computer controlledsystems that may be fitted to the vehicle.

Any faults are transmitted from one system toanother in the same direction ascommunication takes place (see arrows).

B C D

E

FA

1 1 5

4 1 2

G

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Brake sensor functions

How the auxiliary brake system controls areused is described in the Driver's manual.

Brake pedal sensorThe brake pedal sensor consists of apotentiometer that sends an analogue voltage topin 23 on the control unit. The signal informsthe control unit of the requested brake torque.

The potentiometer is built into the footbrakevalve. The graph below shows how the voltageincreases as the brake pedal is depressed.

Note: Note that the potentiometer already givesa voltage, approx. 0.5 V, before the brake pedalis depressed.

The control unit disregards the position of thebrake pedal if the AUT switch is OFF. In thiscase, automatic downhill speed control isdisengaged. In addition, the retarder brakingwhich takes place at the beginning of brakepedal travel ceases 1i.e. before the wheel brakesare applied.

1.The torque level is determined by the configuration. Seegraph under the headline Configuration, Configuration codes.

A fault in the ABS/EBS system up to andincluding EBS version 2.1 will also cause thecontrol unit to ignore the signal from the brakepedal sensor. This applies as long as the ABSwarning lamp is illuminated. When the lampgoes out, the control unit once again takes theposition of the brake pedal into consideration.The control unit receives the message about theABS/EBS fault on pin 14.

The brake pedal sensor is adjusted in such away that the voltage starts to rise as soon asthe pedal is actuated. The voltage should bewithin the grey zone. When the pedal is in thereleased position, the potentiometer providesapprox. 0.5 V. Voltage increases up to approx.4.5 V when the brake pedal is fully depressed.

U(volt)

5

4

3

2

1

0 Max

1 1 6 0 8 6

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Retarder CAN and EBS

For trucks with EBS from version 2.2 onwardswhich have the retarder configuration Braketorque via CAN, the EBS system will havepriority over the retarder and via CAN

messages request the desired brake torque fromthe retarder when the brake pedal is depressed.Pin 23 on the retarder control unit is thereforenot connected on these vehicles.

Application of the wheel brakes and theretarder is controlled completely by EBS whenthe brake pedal is depressed, so for thesevehicles, no brake pedal characteristics areconfigured.

If faults occur in ABS/EBS, the option of

retarder control by depressing the brake pedalis removed by the EBS ceasing to send theCAN message "ABS fully operational".Retarder control by depressing the brake pedalis not possible as long as the CAN message isnot sent. The retarder control unit receives themessage "ABS/EBS fault" on the CAN cables,pins 39 and 40. The ABS/EBS warning lamp isilluminated as long as the fault is active.

Note: The ABS/EBS warning lamp can beilluminated without the option brake pedalactivation of the retarder being disconnected,i.e. the retarder is not disconnected for all typesof EBS faults from version 2.2 onwards.

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Hand lever sensor

The control unit receives the signal from thehand lever on pin 8. The signal informs thecontrol unit of the requested brake torque.

The hand lever has six fixed positions. The fivebraking positions correspond to torque levels of500, 1000, 1500, 2000 and 3000 Nm. In themax. position, the exhaust brake is alsoengaged 1. This occurs internally in the controlunit. Hence there is no contact for this purposein the hand lever sensor.

1.Provided that the exhaust brake switch on the instrument panelis on.

0

1

2

3

4

1 1 4

6 9 9

5

The hand lever has a sensor which provides an

analogue voltage to the control unit. Thisvoltage increases the more the lever is pulleddown.

U(volt)

5

4

3

2

1

0 1 2 3 4 5 Max

1 1 6 0 8 7

The voltage from the hand lever sensor shouldbe within the grey zone. In position 0, the

potentiometer shows approx. 0.5 V, and whenthe lever is moved to the max. position, about4.5 V.

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System functions

Stop light

The stop light (and an indicator lamp that is

standard only on trucks without ABS), isactivated by the control unit under thefollowing conditions.

The stop light illuminates if the braketorque requested at the lever or brake pedalexceeds 450 Nm.

The stop light also illuminates if thedownhill speed control regulator in thecontrol unit requests 900 Nm or more.

The stop light goes out when the retarderbrake torque drops below 300 Nm.

In certain countries it is illegal for the stop lightto illuminate during retarder braking. Thisfeature can be deactivated by removal of stoplight relay R8.

Limiting at high temperatures

The braking power of the retarder is reduced if

the cooling system cannot manage to dissipatethe heat generated. The driver can increase thecooling capacity by changing down so that theengine runs at a higher engine speed. Coolingcapacity, and thus braking power, is directlyproportional to the engine speed.

If the retarder is not capable of holding thespeed, the driver should brake, change downand try again at a lower road speed. When thecoolant starts to return to its normaltemperature, the retarder will gradually regain

its original braking power.The graph below shows how the availablebraking capacity of the retarder is decreased athigh coolant temperatures.

The control unit monitors both brake torqueand brake power with regard to thetemperature. The temperature value is takenfrom both sensors at the outlet from theretarder oil cooler.

The configuration governs the maximum permitted magnitude of the power and torquein the vehicle. However, braking capacityalways decreases according to the abovegraph.

Retarder CAN with fan control

From 0005 certain vehicles are equipped withengine fan control.

When the retarder configuration "Engine fancontrol" is selected, the retarder control unitwill send CAN messages with the desiredengagement level of the engine fan to the EDCcontrol unit. The engagement level depends onthe coolant temperature.

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ABS/EBS communication, general

Signals from the ABS system about ABScontrol interrupt retarder braking within0.2 seconds. This is done by the control unitsimultaneously breaking the current to thesolenoid for compressed air supply 1 and to theproportional valve. In this way, the compressedair, that held the braking oil in the retarder, isreleased. The power to the exhaust brakesolenoid valve is interrupted simultaneously.

ABS control

The auxiliary brake control unit is immediatelynotified on pin 35 that ABS control has begun.Retarder braking interferes with ABS control.

The ABS system disconnects the auxiliarybrake during ABS control, in order to give theABS system free scope. Afterwards, whenABS control has ceased, the driver can againuse the auxiliary brake.

If it was downhill speed control that wasinterrupted by ABS control, this is gentlyrestored as soon as ABS control ceases.

For trucks with retarder configuration Braketorque via CAN (from EBS version 2.2onwards) the signal ABS control is sent to theretarder as a CAN message. Thecommunication cables CAN LOW and CANHIGH are connected to pins 39 and 40 on theretarder.

1.Called ON/OFF in the wiring diagram in Main group 16.From 9908 for trucks and from 9910 for buses, this valve is apart of component V97.

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EDC communication, general

EDC system, PWM signal

The auxiliary brake control unit senses thethrottle position of the EDC engine by readingthe pulse width modulated (PWM) signal.Pulse width increases with increased throttleactivation.

The auxiliary brake control unit receives thePWM signal on pin 12. The signal is illustratedin the figures below.

The PWM signal is a constant frequency squarewave. The voltage level U is also constant. Thevariable is the activation time, calculated as a

percentage of each cycle.The PWM signal carries information veryaccurately to the control units. The auxiliarybrake control unit will immediately generate afault code if the PWM signal seemsimplausible.

Note: The PWM signal cannot be reliably readusing an ordinary multimeter. Instead, use thefault codes to locate the cause of any possiblemalfunctions.

A Cycle time A PWM signal with a pulse width of 10%indicates zero torque.

A Cycle time A PWM signal with a pulse width of 90%indicates maximum torque.

10%

U

T

A 1 0 4

9 6 6

U

T

A 1 0 4

9 6 7

90%

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Exhaust brake

Activation

The exhaust brake 1 is not controlled by the

driver but by the control unit.The working parts of the auxiliary brakei.e. the exhaust brake and the retarder, havedifferent effects at different speeds. On thebasis of the road speed, the control unit candecide how to achieve optimum braking andthen activate the exhaust brake, retarder orboth.

One condition for the activation of the exhaustbrake by the retarder control unit is that the

main exhaust brake switch (applies only tocertain vehicles) on the instrument panel is on.

The exhaust brake is activated:

if the brake torque requested from the handlever exceeds 2700 Nm.

if the control unit is configured forautomatic exhaust brake and the requestedbrake torque from the brake pedal sensorexceeds 500 Nm.

if the downhill speed control regulatorintegrated in the control unit requestsexhaust braking.

The control unit sends the output signal frompin 17 to the exhaust brake or to the exhaustbrake control unit EEB.

1.Some buses are not equipped with exhaust braking.

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Disengagement

The exhaust brake is disengaged as follows:

if the clutch pedal is depressed.

if the accelerator pedal is depressed.

if the engine speed drops below 800 -900 rpm; this is done in order to reduceexhaust emissions.

if the PWM signal from the EDC is greaterthan 15%; this indicates a certain throttleposition.

if the ABS/EBS is active.

if there is a fault in the ABS/EBS system,

exhaust braking requested via the brakepedal will be interrupted, which is a legalrequirement. The exhaust brake canhowever, be activated using the hand leveror a retrofitted floor switch.

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EEB

The EEB has an electronic control unit forcontrol of the exhaust brake and an automaticfunction for the white smoke limiter. With EEBand proportional valve V1 a stepless utilisation

of the exhaust brake is achieved, as opposed toEXB with solenoid valve and automaticretarder operation.

Retarder with Opticruise and EEB has a floorswitch for manual activation of the exhaustbrake.

When activated, the chain of events can bedifferent depending on how long the floorswitch is kept depressed. The signal is appliedto pin 51. Depressing the switch momentarily

sends a signal from pin 54 to the Opticruisecontrol unit requesting Opticruise engine brakeprogram. If the pedal is depressed for a longerperiod, the signal is sent to pin 54 and pin 17and then on to the exhaust brake control unit.

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MBP output

The control unit is equipped with a specialoutput, MBP, at pin 54. MBP is the Swedishabbreviation for engine brake program.

The MBP output is intended forcommunication with the Opticruise controlunit. The function of the MBP output is torequest the Opticruise to change down earlierand at a higher engine speed than normal, inorder to maintain high coolant flow and soincrease the length of time the retarder can beused.

The MBP output is activated as follows:

if retarder torque exceeds 450 Nm whilst

the coolant temperature exceeds 90 C andengine speed drops below 1400 rpm.

if the torque requested torque using thehand lever exceeds 2700 Nm whilst theactual brake torque exceeds 450 Nm.

if the exhaust brake floor switch isactivated.

if the brake torque exceeds 450 Nm whilstdownhill speed control is engaged and the

expected propeller shaft speed is exceededby 125 rpm.

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Warming up the driver and passengercompartments

The retarder can be used to warm up theinterior of the vehicle. This is very usefulduring cold weather, especially in buses

The warm-up function is used in two differentways, depending on whether or not the vehiclehas ABS/EBS. It works as follows.

Vehicles with ABS/EBS

Warm-up can only be activated if the coolanttemperature is below 70 C when the startervoltage is switched on.

The maximum available power calculated inkW is halved until the coolant reaches 50 C.

The warm-up function is automaticallyinterrupted when the coolant reaches 85 C.

Vehicles without ABS/EBS

Vehicles without ABS/EBS do not have anyautomated operation of warm-up. Warm-up isachieved simply by applying the acceleratorand retarder braking with the lever

simultaneously. In principle, it is normalcontrol unit regulation which limits how longwarm-up can continue, but the temperatureinside the vehicle reaches a comfortable levellong before this. See the graph under theheading Limiting at high temperatures.

The maximum available power calculated inkW is halved until the coolant reaches 50 C.

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Configuration

General

The control unit contains all the computer

programs necessary for all trucks and buses.

The control unit must be configured so that ituses the correct computer program for therelevant Scania vehicle. This is simply theequivalent of the code plug fitted to other, lessmodern control units, e.g.for CAG, CS andScania automatic gearboxes.

Note: Incorrect configuration will alwaysresult in reduced performance and/or service

life.

The required control unit configuration isentered using a PC during manufacture. As aspare part however, the auxiliary brake controlunit is only delivered configured for truckswith ABS , which is the most commonconfiguration.

If necessary, the configuration can be changedusing a PC and Scania Programmer, which is

available on CD-ROM. The standardconfiguration for the vehicle concerned mustbe used in all but exceptional circumstances.This is described in greater detail under theheading, Configuration, explanations.

The configuration can also be read without aPC, in the form of a configuration code, a socalled flashing code, from the diagnostic lamp2 which is marked RET.

Old type of diagnostics panel up to 9910

New type of diagnostics panel from 9911

E D C

A T C

0 5

_ 5 1 6 0

0 5

_ 5 1 6 1

1 2

0 5

_ 5 1 6 1

1 1 4

5 9 5

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Configuration codes

Control units up to 9911

The configuration codes consist of 3 digits. Thedigits are flashed out as follows:1st digit - 1.5 s pause - 2nd digit - 1.5 s pause -3rd digit - 4.5 s pause, end. After that followany fault codes.

Standard versions:

Trucks equipped with ABS/EBS haveconfiguration code 468.

Trucks without ABS/EBS have 453.

Buses equipped with ABS have 458 (438 forearlier versions).

Buses without ABS have 453.

Control units from November 1999

Vehicles built from 9911 have a new retardercontrol unit with one more configuration digit.The following can be configured using thisfourth digit:

Brake torque via CAN, (from EBS version2.2 onwards).

Engine fan control.

Note: This type of control unit is introduced asa spare part for both trucks and buses from9911. However, buses must not be configuredwith EBS CAN. If a bus is found to beconfigured with "Brake torque via CAN (fromEBS version 2.2 onwards)", trouble shootingshould begin immediately and the control unitbe reprogrammed using Scania Programmer.

etc

1 1 5

8 6 3

1 1 5

8 6 4

4 6 8

4 85 1 1 5 8 6 6

The digits are flashed out as follows:1st digit - 1.5 s pause - 2nd digit - 1.5 s pause -3rd digit - 1.5 s pause - 4th digit - 4.5 s pause,end. After that follow any fault codes.

Standard versions:

Trucks equipped with ABS have configurationcode 4681.

Trucks with EBS via CAN have configurationcode 4682.

Trucks without ABS/EBS have 4531.

Buses with ABS have 4581.

Buses without ABS have 4531.

1 1 5

4 1 3

etc.

1 1 5

7 6 34 6 8 2

1 1 5

4 1 54 5 8 1

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Significance of configuration codes

First digit a

1 Max. retarder torque 2400 Nm, of which 1500 Nm before the wheel brakes areapplied




Second digit

1 Without automatic downhill speed control, 300 kW retarder power

2 With automatic downhill speed control, 300 kW retarder power





7 Without automatic downhill speed control, the retarder power is controlledautomatically

8 With automatic downhill speed control, the retarder power is controlledautomatically

Third digit

1 Without hand lever control, without brake pedal control, without manualdownhill speed control

2 Without hand lever control, with brake pedal control, without manual downhillspeed control

3 With hand lever control, without brake pedal control, without manual downhillspeed control

4 With hand lever control, with brake pedal control, without manual downhillspeed control

5 Without hand lever control, without brake pedal control, with manual downhillspeed control

6 Without hand lever control, with brake pedal control, with manual downhill

speed control

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a: Control units on trucks built from 9911 mayhave configuration Brake torque via CAN, fromEBS version 2.2 onwards. The application ofwheel brakes and retarder is then controlledentirely by EBS when the brake pedal isactivated, and therefore no brake pedalcharacteristics are configured for these vehicles.This type of control unit is introduced as a sparepart for both trucks and buses from 9911.

b: Vehicles built from 9911 have a new retardercontrol unit with one more configuration digit.This type of control unit is introduced as a sparepart for both trucks and buses from 9911. Thecontrol unit should only be configuredaccording to the table, if other configurations arepresent, this must be changed using Scania

Programmer.

7 With hand lever control, without brake pedal control, with manual downhillspeed control

8 With hand lever control, with brake pedal control, with manual downhill speedcontrol

Fourth digit b

1 Without Brake torque via CAN, from EBS version 2.2, without Engine fancontrol.

2 With Brake torque via CAN, from EBS version 2.2, without Engine fan control.

3 -

4 -5 With Engine fan control, without Brake torque via CAN.

6 With Engine fan control, with Brake torque via CAN, from EBS version 2.2.

Third digit

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Configuration, explanations

Configuring the control unit instead of using arange of different code plugs simplifies bothmanagement of parts and any modifications tothe vehicle in question. Modifications may beas simple as swapping the standard alternatorfor a more powerful one, with a differentnumber of terminals and/or gear ratio.Modifications must always be carried out aftercareful consideration. Configuration must thenbe checked and updated.

The control unit must always have the correctand complete information 1. Otherwise, it willnot be able to perform its tasks in the correctmanner.

Never attempt to improve the performance ofthe auxiliary brake system yourself, byexperimenting with the configuration. Eachstandard configuration has been developedusing the collective expertise of Scania in orderto achieve the best combination of brakingcapacity, running costs and ride comfort.

The configuration governs, among other things,the following:

Which controls can be used to operate theauxiliary brake system.

Whether downhill speed control is to beincluded and if so, how this should beoperated. Applies only to vehicles withABS/EBS.

The maximum power of the retardercalculated in kW. The power must belimited to the maximum amount of heatwhich can be dissipated by the vehicle s

ordinary cooling system. The maximum torque of the retarder

calculated in Nm. It is of course desirablefor vehicles with a high gross weight tohave high brake torque, but the torque mustbe limited to a level which the central gearcan tolerate without causing prematurewear.

1.By information we mean everything from software and inputsignals to correct configuration.

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Brake pedal characteristics , i.e. how hardthe retarder brakes before the wheel brakesare applied. This is normally 2000 Nm forboth buses and trucks. Trucksmanufactured from 9911 may have theconfiguration Brake torque via CAN, fromEBS version 2.2 onwards. For thesevehicles, no brake pedal characteristics areconfigured.

Available cooling capacity in the coolingsystem. Alternator frequency must becorrectly specified or the control unit willmiscalculate the engine speed and thuscoolant flow at any given time. Incorrectdata can for example cause problems withoverheating or unnecessarily low retarder

power. Communication with EBS via CAN is

introduced on trucks from 9911. Theconfiguration Brake torque via CAN, fromEBS version 2.2 onwards, is thereforeselected. Application of the wheel brakesand retarder is fully controlled by EBSwhen the brake pedal is depressed.

Retarder control of the engine fan isintroduced on certain engine types in

trucks from 0005. When the configuration"Engine fan control" is selected, theretarder control unit will send CANmessages with the desired engagementlevel of the engine fan to the EDC controlunit. The engagement level depends on thecoolant temperature.

The above can be a guide in such cases where acertain fault is suspected as being caused byincorrect configuration.

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Control unit as spare part

Every control unit from our parts department isconfigured for trucks with ABS. In suchvehicles, and only there, the control unit may beused as delivered. Otherwise, the configurationmust be changed using a PC and ScaniaProgrammer, which is available on CD-ROM.

a: Certain buses have no exhaust brake at all.

b: Applies to the construction and design of theactual retarder.

c: Trucks built from 9911 may have theconfiguration Brake torque via CAN, from EBSversion 2.2 onwards. For these vehicles, nobrake pedal characteristics are configured.

Function Standard setting asspare part

Alternative

Operation with brake pedal yes yes / no

Operation with hand lever yes yes / no

Manual activation of downhill speed control yes yes / no

Automatic activation of downhill speed control yes yes / noAutomatic activation of exhaust brake a no yes / no

Retarder version b 00 00

Retarder power 500 kW 300 / 400 / 500 kW

Retarder torque 3000 Nm 2400 / 3000 Nm

Brake pedal characteristics c 2000 Nm 1500 / 2000 Nm

Compensation of current to the proportional valve d 0 mA. +/- 50 mA

Alternator frequency (Truck, 6 poles) at engine speed500 rpm

172 Hz 100 - 255 Hz

Alternator frequency (Bus, 8 poles) at engine speed500 rpm

200 Hz 100 - 255 Hz

Alternator frequency (Truck, 8 poles, 90 A) at enginespeed 500 rpm

230 Hz 100 - 255 Hz

Communication with EBS via CAN e no yes / no

Communication with EDC via CAN, engine fan

control

no yes / no

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Control unit connections

The table below shows which input signals thecontrol unit can receive and which pin is usedfor which signal.

Most, but not all, input signals are in the form ofa positive voltage.

The * symbol beside the pin number indicatesthat the input signal in question is activatedwhen the control circuit is earthed.

Control unit input signals

Pin Input signal

8 Hand lever position

12 PWM signal from EDC.13* Accelerator pedal switch

14* ABS/EBS reports ABS/EBS fault. For trucks with retarder configurationBrake torque via CAN, from EBS version 2.2 onwards, the signal ABS/EBSfault is sent to the retarder as a CAN message. The CAN cables are connectedto pins 39 and 40, see Other connections.

16 Propeller shaft speed, i.e. current road speed

23 Brake pedal position. The input signal is not used for trucks with retarderconfiguration Brake torque via CAN, from EBS version 2.2 onwards; instead,

in these vehicles the EBS control unit sends the required retarder brake torquevia CAN. The CAN cables are connected to pins 39 and 40, see Otherconnections.

25 Temperature sensor 1

30* Diagnostics switch

31 AUT switch for automatic activation of downhill speed control.

32* Switch for manual activation of downhill speed control

33* Exhaust brake switch on instrument panel

34 Engine speed, i.e. current cooling capacity.

35* ABS/EBS announces ABS control. For trucks with retarder configurationBrake torque via CAN (from EBS version 2.2 onwards) the signal ABScontrol is sent to the retarder as a CAN message. The CAN cables areconnected to pins 39 and 40, see Other connections.

43 Temperature sensor 2

50* Clutch pedal switch

51 Foot-operated switch for exhaust brake, not standard equipment

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The table below shows which output signals thecontrol unit can send and which terminal pin isused for which signal.

Earthing points, power supplies etc. are coveredunder the heading Other connections.

Most, but not all, output signals are activated bya positive voltage in the control circuit.

The * symbol beside the pin number indicatesthat the output signal is instead activated by thecontrol circuit being earthed.

Control unit output signals

Pin Output signal

2 Proportional valve (+) for torque control of the retarder

17 Solenoid valve (or control unit) for exhaust brake

18 Request to EDC for disengagement of cruise control.

30* Retarder diagnostic lamp on instrument panel

36 RET warning lamp on instrument panel

38 Proportional valve (-) for torque control of the retarder

52 Solenoid valve for oil accumulator

53 Solenoid valve for compressed air supply54 Request for engine braking program, MBP

55* Stop light relay

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Other connections

Pin Connections

1 System earth (0 V)

4 Brake pedal sensor (-)

6 Temperature sensor 1 (-)

7 Temperature sensor 2 (-)

15 L cable, diagnostic socket

37 System voltage (24 V)

19 System voltage (24 V)

20 System earth (0 V)

26 Hand lever sensor (-)39 Communication cable, CAN LOW. Dependant upon how the retarder control

unit is configured and how the truck is equipped, this cable is used forcommunication with EBS, from EBS version 2.2 onwards, and EDC.

40 Communication cable, CAN HIGH. Dependant upon how the retarder controlunit is configured and how the truck is equipped, this cable is used forcommunication with EBS, from EBS version 2.2 onwards, and EDC.

41 Brake pedal sensor (+)

44 Hand lever sensor (+)

49 K cable, diagnostic socket

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1050t15b.mkr Scania CV AB 1999, Sweden 35

Warning system

General

Introduction

If any faults arise, the control unit will initiate avariety of measures. This is to prevent the faultcausing expensive damage.

If a fault occurs, the control unit will also lightthe warning lamp (RET) on the instrumentpanel. If the fault ceases, the warning lampusually goes out by itself. This is not alwaysthe case and depends on the nature of the fault.

RET

1 0

1 8 4 5

The lamp should come on for a second everytime the ignition is turned on (test).

Certain types of fault disable downhill speedcontrol, for instance, or make it impossible touse the brake pedal to initiate downhill speedcontrol. However, the lever usually still workseven when such faults have developed. Thereason may be a fault in the ABS/EBS system,for example, and in such a case the ABS/EBSlamp should come on.

The vehicle must get up to speed for theABS/EBS lamp to go out. Before this, the RETlamp cannot go out either, in case the fault isone which concerns auxiliary brake and ABS/ EBS interaction.

Resetting of the warning system is carried outon two levels. The flashing codes are erasedand the warning lamp goes out. Fault codes thatare read using a PC can only be erased using aPC. This is described under the heading Finalerasure of fault codes using a PC.

RET

1 0

1 8 4 5

ABS 1 0

2 5 7 1

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Why fault codes are generated

The control unit reacts quickly and accordingto certain instructions. In practice, the controlunit works with long series of conditions,signals, routines and commands thatcontinuously succeed each other.

When the control unit discovers a fault, orsomething which it interprets as abnormal, itimmediately reacts and generates a fault code.The warning system can generate about 40different fault codes depending on the nature ofthe fault. Fault codes are generally veryaccurate.

LimitationsDespite the advanced software, a fault mayarise which the control unit is unable todistinguish from something which may occurunder normal operation. If this is the case, nofault code is generated. There is always a limitto how complete the monitoring can be. Theabove applies to all types of control units.

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Warning lamp, faultindication

Warning lamp

If the fault ceases, the warning lamp willgenerally go out automatically. This may seemcoincidental to some drivers, but has of coursefunctional or safety reasons.

More information on reasons for fault codescan be found in SD and in the work descriptionfor trouble shooting.

RET

1 0

1 8 4 5

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Resetting the warningsystem

General

The warning system may occasionally needresetting. Someone may have, for exampledisconnected a cable harness whilst the ignitionwas turned on. This is quite a commonoccurrence. The control unit will then interpretit as a fault. This will also illuminate thewarning lamp RET.

Resetting of the warning system is carried outat two levels and is described below.

Erasing flashing codes

This extinguishes the RET warning lamp anderases the flashing codes shown by thediagnostic lamp 2. The fault codes willhowever remain in another memory that canonly be accessed using a PC, see Final erasureof fault codes using a PC.

1 Press in the switch 1 and keep it depressed.

RET 1 0

1 8 4 5

Old version of diagnostic panel up to andincluding 9910

New version of diagnostic panel from 9911

1 0

2 0 9 7

1 2

0 5

_ 5 1 6 1

1 1 5

5 2 6

1, 2

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Documents

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