product manual abs 6 standard anti-lock braking system katalogoi/auto/abs6y029757e002.pdfan...

S y s t e m s f o r C o m m e r c i a l V e h i c l e s

Product Manual ABS 6 Standard Anti-lock Braking System

• Basic Principles of Operation of the System

• Component Descriptions

• Troubleshooting and Fault-Finding

• Service Guidance to ensure Safe and Efficient Operation

�

Training Nutzfahrzeug Bremssysteme

�

Contents

Contents 3

Disclaimer 4

SafetyChecks 5

1. GeneralInformation 6

1.1 ServiceIntervals 6

1.2 PrinciplesofAnti-lockBrakingSystem(ABS)Operation 7

1.2.1 Introduction 7

1.2.2 Operation 9

1.3 GeneralAdvicewhenworkingwithABS 14

1.3.1 DosandDon’tsforDrivers/Operators 14

1.3.2 DosandDon’tsforABSelectricalcomponentsandcabling 15

1.3.3 DosandDon’tsforABSpneumaticcomponentsandpipework 17

1.4 TroubleshootingandFault-finding 18

1.4.1 NormalOperation 18

1.4.2 Start-upCheck 18

1.4.3 FaultDetection 18

1.4.4 UsingBlinkCodes 18

1.4.5 ConfigurationBlinkCodes 19

1.4.6 FaultBlinkCodes 21

1.4.7 ErasingFaultCodesfromtheECUmemory 26

1.4.8 PCDiagnostics 27

2. SystemComponents 28

2.1 ElectronicControlUnit(ECU) 28

2.2 ABSWarningLamp 29

2.3 SensingRing 30

2.4 WheelSpeedSensor 31

2.5 SensorExtensionCable 34

2.6 PressureModulatorValves 35

2.7 VOSSplugconnectionsystem230(assemblyinstructions) 41

3. WiringDiagrams 43

��

Theinformationcontainedinthisdocumentisintendedfortheexclusiveuseoftrainedpersonswithinthecommercialvehicleindustry,andmustnotbepassedontoanythirdparty.

All recommendations regarding products and their servicing or usage are with reference toKnorr-Bremse products and should not be considered applicable to products from othermanufacturers.

Thisinformationdoesnotpurporttobeall-inclusiveandnoresponsibilityisassumedasaresultof its use. We cannot accept any liability nor offer any guarantee regarding data accuracy,completeness or timeliness. The information does not represent any guarantee or ensuredcharacteristicsoftheProductsorSystemsdescribed.

No liability can be accepted based on the information, its use, recommendations or adviceprovided.Innoeventmaywebeheldliableforanydamageorlossexceptinthecaseofwilfulintentorgrossnegligenceonourpart,orifanymandatorylegalprovisionsapply.

AnylegaldisputesarisingfromtheuseofthisinformationshallbesubjecttoGermanlaw.

ThisdisclaimerisanEnglishtranslationofaGermantext,whichshouldbereferredtoforalllegalpurposes.

Disclaimer

�


�

SafetyChecks

Beforeworkingonoraroundairbrakingsystemsanddevices,thefollowingprecautionsshouldbeobserved:

Stoptheenginebeforeworkingunderavehicle.

Always chock the wheels because depleting vehicle air system pressure may cause thevehicletoroll.Keephandsawayfromactuatorpushrodsandslackadjusters/brakelevers;theymayapplyassystempressuredrops.

Examineallpipeworkforsignsofkinks,dents,abrasion,dryingoutoroverheating.

Checktheattachmentofallpipework;itshouldbesupportedsothatitcannotabradeorbesubjectedtoexcessiveheat.

Neverconnectordisconnectahoseorlinecontainingairpressure,itmaywhipasairescapes.Neverremoveadeviceorpipeplugunlessyouaresurethatallsystempressurehasbeendepleted.

Neverexceedrecommendedvaluesofmaximumairpressureandalwayswearsafetyglasseswhenworkingwithairpressuresystems.Neverlookintoairjetsordirectthematanyone.

Never attempt to dismantle a device until you have read and understood recommendedprocedures. Some units contain powerful springs and injury can result if not properlydismantled.Useonlycorrecttoolsandobserveallprecautionsrelativetotheuseofthesetools.

•

•

•

•

•

•

•

��

1.GeneralInformation

1.1 ServiceIntervals

3 years or 300,000 km – check the functionalityof thesystemusingspecialistKnorr-Bremse testequipment.Inthecaseoffailure,thedefectivepartistobereplaced–theservicingofadefectivepartis not permitted. There are no serviceable ABScomponentsinthesystem.

Note:

TheelectricalfunctionalityoftheABScomponents–ElectronicControlUnit,modulators,sensorsandcabling–ischeckedautomaticallybyin-builtselfdiagnosticsoftwareandthedriveriswarnedofanymalfunctionorfailure.

Additional checks:

In addition to the above and legally requiredperiodic vehicle inspection, it is recommendedthatsimpleroutineinspectionsofageneralnaturebecarriedouttomaintainthebrakingsystematahighleveloffunctionality.

These simple routine inspections should be:

On a monthly basis remove any moisturein the reservoirs, using the reservoir drainvalves.Iftheamountofmoistureisexcessivechecktheoperationoftheairdryerorothermoistureextractiondevices

On a 6-monthly / 50,000 km basis checkthe complete braking system for excessiveleakage during a maximum pressure footbrakeapplicationwiththevehiclestationaryandtheparkingbrakereleased.

1)

2)

�


�


1.2 PrinciplesofAnti-lockBraking System(ABS)Operation

1.2.1 Introduction

An Anti-lock Braking System (ABS) is used toprevent the wheels of a vehicle locking whilstbraking.

Itiswellknownthatawheeloperatingonweticehas very little friction (adhesion) and hence cantransmitlittlebrakingortractionefforttotheice.Ondryasphaltthereismuchmorefriction(adhesion)availableandoptimumbrakingandtractioncanbeachieved.Thefriction(μ)betweenthetyreandtheroadiscreatedbyrelativemovementbetweentheirtwosurfaces,i.e.differenceinsurfacespeeds,andthisiscalled‘slip’(λ),whichisnormallyexpressedasapercentage:

0%slipmeansthatthesurfacespeedofthetyreandtheroadareequal.

100%slipwhenbrakingmeansthatthewheelhasstoppedrotating,i.e.thesurfacespeedofthetyreiszero,butthevehicleisstillinmotion(maximumdifferenceinsurfacespeeds–fulllock).

•

•

Smallpercentagesofsliparerequiredtocreatethemaximumavailable frictionbetween the tyreandthe road, but should the slip become excessive(generally >20%) the wheel is considered tobe locked under braking (or spinning underacceleration). The level of friction present isdependentonmany factors, themost significantof which are the condition of the tyre and theroadsurfaceandthepercentageof‘slip’betweenthetyreandtheroad.Fig.1showssometypicalcurvesfortheleveloffrictionpresentondifferentroad surfaces with different levels of slip. Mostofthecurvesshowthattheleveloffrictiondropsonly slightly as the wheel starts to lock and inthese cases, once the wheel has locked, it willcontinue to transmit a high percentage of themaximum braking effort available. However, inthecaseofwetasphalt,oncethewheelstartstolock,thefrictiondropssignificantlyandthewheelwillrapidlymoveintoa“fulllock”situation.Thisisbecausethewheelisabletotransmitlessbrakingeffortcausingincreasedslip,whichinturnreducestheleveloffrictionandbraking.

Fig. 1

��


Onceawheel has started to lock then it cannolongertransmitthenecessarytorqueforthedesiredbrakingand it isalsounabletotransmiteffectivelateralforcesforsteeringorcornering,i.e.thewheel‘slides’.Fig.2showshowthefrictionavailableforcorneringfallsdramaticallywhenthewheelstartstolockduetobraking.Theinabilityofawheelonasteeringaxletotransmitlateral(cornering)forcemeansthatthevehiclewillnolongerbeunderthefulldirectionalcontrolofthedriver.

Itisthereforeimportantthatwheelsareprevented,whenever possible, from locking under brakingconditions so that the directional stability of thevehicleismaintained.

ABSwillpreventlockingofthewheelsonallroadsurfacesandprovidethedriverwiththedirectionalcontrolthatheneeds.Inmostcases,bypreventingwheellock,ABSalsoresultsinareducedstoppingdistanceforthevehicle.

ABSisanadditiontoabasicservicebrakingsystemusedonacommercialvehicleorbusandinvolvestheinstallationofanElectronicControlUnit(ECU),pressure modulator valves, sensing rings, wheelspeed sensors and associated electrical wiring(seeFig.3).

Fig. 2

�


�

1.Wheelspeedsensorandsensingring

2.Pressuremodulatorvalve

3.ElectronicControlUnit(ECU)

Fig. 3: 4 x 2 Vehicle, 4S/4M ABS

1.2.2 Operation

ABSconstantlymonitorstherotationalspeedofallwheelsandcomparesthespeedofeachwheeltoanaverageofallwheelspeeds(ReferenceSpeed)calculatedbytheElectronicControlUnit(ECU).Bydoingthisthesystemcandetectwhenoneormorewheelsslowdownexcessively.Asensingringandwheel speed sensor are installed at each wheeland,when thewheel rotates, they react togethertosendasinusoidalelectricalsignal to theECU.ByanalysingthefrequencyofthissignaltheECUcan monitor the rotational speed of each wheelandcalculateitsaccelerationordeceleration.

Whenbrakingtakesplace,atanymomentintimetheECUcandetermine if the rotationalspeedofanywheelvariesfromtheReferenceSpeed.Ifonewheel is on a slippery surface and is unable to

supportthelevelofbrakingthatitisbeingaskedto contribute then the wheel speed will drop inrelationtotheReferenceSpeed,i.e.the‘slip’anddecelerationofthatwheelwillstarttoincrease.TheECUwillnormallydetectthisduringtheapplicationof the brake and before the wheel becomeslocked.AssoonasthisdeviationofwheelspeedisdetectedtheECUwillnolongerincludethatwheelinitsReferenceSpeedcalculation.

Once the ECU detects excessive slip or a rapidchange in deceleration on a wheel (see Fig. 4)it sends an electrical signal to the appropriatepressuremodulatorvalvetoreleasethepressurein the service brake actuator on that wheel (seealsoSection2.6).


1010

italsosendsasignaltoswitchofftheendurancebraking device until braking returns to normal.The signal to endurance braking device can befromarelayinsidetheECUorviaaCANdatalinkconformingtoSAEJ1939.

Fig. 5


If an ABS equipped vehicle is fitted with an“Endurance Braking Device”, for example anEngineExhaustBrakeorDriveLineRetarder,whentheECUsignals thepressuremodulatorvalve tointervene in the control of the brake application

Fig. 4

11


11


Fig. 6

Whenthepressuremodulatorvalvehasexhaustedsufficient air pressure from the service brakeactuator, the adhesion between the tyre and theroadwillcausetherotationalspeedof thewheelto increase. The ECU detects this increase inwheelspeedandsendsanelectricalsignaltothepressure modulator valve to stop exhausting theairpressure(seeFig.5).

Astherotationalspeedofthiswheelcontinuestoincrease,theECUwillsendanelectricalsignaltotheappropriatepressuremodulatorvalve to re-applytheservicebrakeonthatwheel.Thepressurewillbeincreasedintheservicebrakeactuatorinstepsbypulsingthepressuremodulatorvalvesolenoids.AttheendofeachsteppedincreaseinpressuretheECUwillchecktoensurethattherotationspeedofthewheel is increasingtowardsthespeedof theotherwheelsandifitistheECUwillsignalafurthersteppedincreaseinpressure(seeFig.6).Oncethespeedof thewheelapproaches thatof theotherwheelstheECUwillagainincludeitsinputintotheReferenceSpeedcalculation.

1212


Fig. 7

These stepped increases will continue until thepressure in the service brake actuator reachesthe levelsetbythefootvalve. IfatanytimetheECUdetectsthattheslipofthewheelisincreasingagainandthereisarapidchangeindecelerationitwillsignalthepressuremodulatorvalvetoexhaustagain thepressure in theservicebrakeactuator.This cycle of exhausting the brake pressure andthen re-applying it insmall steps (seeFig.7)willberepeatedmanytimeseverysecondinordertoobtain themaximumamountofbrakingavailablefrom the wheel and to maintain the directionalstabilityofthevehicle.

Afterseveralexhaustandre-applicationcyclesofthebraketheECUcanpredictthepointatwhichthespeedof thewheelwill start to increaseandso is able to lessen thedegreeof releaseof thebrake. With this smaller release of pressure there-applicationstepswillbeofsmaller incrementsgivingtheABSimprovedcontroloverthebrakingof the wheel thereby contributing to a shorterstoppingdistance..

Thecontrolcycledescribedaboverelatestoonewheel,butitisquiteprobablethatmorethanonewheelonavehiclemayshowatendencyto lockduring a service brake application. If this is the

casethentheECUwillcontrolallwheelsshowingatendencytolockinasimilarmannerwithsomelimitations.

WhenthevehicleisbeingdrivenonaroadsurfacehavingdifferentlevelsofadhesionbetweentheleftandrightsidethenitislikelythatthewheelonthesurfacewiththelowerlevelofadhesionwillshowatendencytolockresultinginanABSinterventionon that wheel. If the wheel with no tendency tolock(onthesurfacewithhigherlevelofadhesion)islefttoprovideanormalservicebrakeapplicationonthatwheelthenasituationwillexistacrosstheaxle with one wheel being fully braked and theotherwheelhaving littleornobraking,dueto itstendencytolock.Thisdifferenceinbrakingacrosstheaxlecan induceayawor turningmomentonthe vehicle which, if on the steering axle of thevehicle,wouldmakeitdifficulttocontrol.Forthisreason the ‘Individual Regulation’ (IR) method ofcontrolintheABS6systemisappliedonlytothedriveaxleofthevehicle.

Inordertominimisetheabove‘yaw’effectonthesteering axle of the vehicle, the ABS6 systemuses‘ModifiedIndividualRegulation’(MIR)onthesteeringaxle.WithMIR,whenonewheelshowsatendencytolockandtheABSintervenestorestrict

1�


1�

or reduce the pressure in the brake actuator onthatwheel,italsolimitsthepressureinthebrakeactuator on the other wheel. This limitation ismanagedbytheECUtoensurethe imbalance inbrakingacross theaxle iswithin limits thatallowthedrivertoretain“steerability”ofthevehicleandheisnotsubjectedto“snatching”ofthesteeringwheel.Underthesecircumstancesthetheoreticalmaximumamountofbrakingthatcouldbeavailableis not achieved on that axle and the stoppingdistancewillbemarginally longerthan if theaxlewere controlled using IR. However, the ability ofthedrivertoretaindirectionalcontrolofthevehicleispreferableinmostcircumstancestoamarginallyshorterstoppingdistance.

The control processes described above areperformedbytheABSsolongasvalidsignalsarebeing sent from the wheel speed sensors to theECU.TheECUrequiresaminimumpeakvoltagebeforeitrecognisesthesignalfromthewheelspeedsensorasvalidandthereafteritusesthefrequency

ofthesignaltomonitortherotationalspeedofthewheel. The speed at which the signals from thewheelspeedsensorsbecomevalid isdependentonthegapbetweenthewheelspeedsensorandthesensingring,butisnormallyintherangeof5to8km/h.Thisisknownasthe‘lockoutspeed’andbelowthisspeedtheECUbecomes inactiveandthereisnoABSfunction.

The system described above relates to a2-axle,towingornon-towing,vehiclewitha4x2configuration(i.e.2drivenwheels)equippedwithawheelspeedsensoroneachofthe4wheelsandapressuremodulatorvalvecontrollingtheservicebrake actuator on each of the 4 wheels. Such asystem is designated 4S/4M, i.e. 4 sensors/4modulators. A 4S/4M system can be used toprovide the ABS function on a 3 axle, towing ornon-towing, vehicle by combining the control oftheactuatorsontheleftandrightsideoftherearbogie(seeFig.8).


Fig. 8: 6 x 4 Vehicle, 4S/4M ABS

1.Wheelspeedsensorandsensingring

2.Pressuremodulatorvalve

3.ElectronicControlUnit(ECU)

1�1�

1.3 GeneralAdvicewhenworking withABS

InorderforABStoworkeffectivelythesystemmustbemaintainedinsuchaconditionthattheelectricalcablinghasminimalelectrical resistanceand thepneumatic piping presents minimal restriction totheflowofairintheservicebrakesystem.IfthesetwocriteriaaremetthentheECUwillreceiveandsend clean, accurate electrical signals and thepressuremodulatorvalveswillbeable tocontrolthepressureintheservicebrakeactuatorsrapidlyandaccurately.

1.3.1 DosandDon’tsforDrivers/ Operators:

Neverswitchoff the ignitionwhiledrivingasthiswillalsoswitchofftheABS.

DonotassumethatwithABSfittedtoavehicleitissafetodrivefasterormoreaggressively.ABSmaynotshortenstoppingdistancesinallsituations.

IftheABSwarninglampcomesonandstayson,thesystemmustbecheckedassoonaspossible(normalbrakingwillstillbeavailablebutwithouttheABSfunction).

Donotattemptto“pump”thebrakesduringa wheel lock situation. The ABS can applyandreleasetherequiredbrakesmuchquickerthanadriver.Inaddition,any“pumping”couldupsettheoperationoftheABS.

TheefficientoperationoftheABSreliesuponthe tyres obtaining the maximum adhesionpossible with the road surface and so theircondition is important. Replace any worn ordamagedtyresattheearliestopportunity.

Fit the same diameter tyres to all wheels,conforming to the vehicle manufacturer’srecommendations.

Ensurethatthetyresarecorrectlyinflatedatalltimes.Atyrerunningwithlowpressurewillhaveareducedrollingradiusandconverselyatyrewithhighpressurewillhaveanincreased

•

•

•

•

•

•

•

rolling radius. Ifone tyrehasa rolling radiusdifferent to theother tyres then its rotationalspeedwilldifferand,ifthisdifferenceisoutsidepredetermined limits, theECUwill indicateafaultandturnofftheABSfunction.

TheefficientoperationoftheABSreliesupontheefficientoperationofthebrakingsystem.Ensurethatclearanceadjustmentismadeforanywornbrake linings so that the strokeoftheservicebrakeactuatorsisattheoptimumlevel.Ensurethatthebrakesaremaintainedtoeliminate“brakesqueal”as itspresencecandistort the electrical signals from the wheelspeed sensor and prevent operation of theABS.

The efficient operation of the ABS relieson reliable wheel speed information beingsupplied by the wheel speed sensors inconjunctionwiththesensingrings.Theserelyoncorrectmaintenanceofthewheelbearingstoensurethattherun-outofthesensingringiswithinacceptablelimits.Alwaysensurethatthewheelrun-outiswithinthemanufacturer’sspecification.

Wheninstallingancillaryelectricalequipmenton the vehicle do not use the electricalsupplytotheABSasapowersourcefortheequipment.

•

•

•


1�


1�

1.3.2 DosandDon’tsforABS electricalcomponentsand cabling

Beforecommencingworkonavehicle,alwayschockthewheelstopreventthevehiclerollingwhenthebrakesarereleased.

Do not connect or disconnect any ABScomponentwiththeignitionswitchedon.

Whencarryingoutanyweldingonthevehiclealways ensure that all electrical connectionsto the ECU are removed temporarily (seeFig.9).VoltagespikescausedbytheweldingequipmentcouldotherwisepossiblydamagetheECU.Neveruseanyelectricalequipmentastheearthfortheweldingequipment.

IftheECUisconnected,neverruntheengineand alternator without a well-connectedbatteryinthecircuit.VoltagespikescausedbythealternatorcouldpossiblydamagetheECUiftheywerenotabsorbedbythebattery.

IfavehiclefittedwithABShasaflatbattery,itcanberechargedwithanexternalchargerorbatteryat thesameratedvoltage.Donotattempt to start a vehicle using a “boosterstart”devicesincethiscouldsupplyexcessivevoltage.

Wheninstallingancillaryelectricalequipmenton the vehicle do not use the electricalsupplytotheABSasapowersourcefortheequipment.

If anyancillaryequipment is installedon thevehicleensure thatanywiringandantennaearenotroutednear totheABSECUorABScabling.

If anymodificationsaremade to the vehiclethat require an increase in the length of thecablesbetweentheECUandthewheelspeedsensors then new purpose-made extensioncablesfromthesystemmanufacturermustbeused,eitherinadditiontoorinplaceofthosealready fitted. These must be the correctlength to suit the installation since loopingofexcesscablemay induce radio frequencyinterferenceandABSmalfunction.

•

•

•

•

•

•

•

•


Fig. 9

1�1�

AnynewABScablesmustberoutedsothat:

Theyareprotectedfromdamageduetostonesthrownupfromtheroad.

Theyarenotpronetobeingsnaggedandrippedoff.

Theyarenot subject toanymechanicalstrainor tensionunder anyconditionofsuspensiontravelorsteeringmovement.

If the insulation of any cable becomesdamaged then the cable must be replaced.Under no circumstances must any cable becutandrejoined(seeFig.10).

When removing and refitting electricalconnectors take great care to ensure thecorrectalignmentoftheplugandsocket.Therearenormally locationspigotsandgrooves inthematingpartstoensurecorrectalignmentand therefore correct electrical connections.Donotattempttoforceanyplugintoasocket– this could result in physical damage tothe connection pins and malfunction of thesystem.

When refitting electrical connectors alwaysensurethattheyarepushedhomefullytogivethe maximum protection from moisture andcontamination.

Whenremovingawheelspeedsensordonotpullonitscable.

•

°

°

°

•

•

•

•

Whenreplacingawheelspeedsensorensurethat there are no sharp bends in the cableclose to thesensorhead. Ifusingcable tiestosecurethecable,thesemustnotbepulledtootightas thiscancausephysicaldamagetothecableandpossibleshortcircuits.Whenreplacingawheel speed sensor always fit anewsensorbushandusethecorrectlubricantbetweenthesensorandthebush.Thesensorshould slide in the bush using only manualpressure.

When refitting any electrical cabling that isprotected by corrugated tubing ensure thatthe tubing is guided such that any waterenteringitwilldrainawayfromanyelectricalconnector.

Should heavy corrosion be found on thepins of an electrical connector the cableassemblyshouldbereplaced.Whenfittingthereplacementcableassembly,ensurethattheweatherproofing of the connector plug andsocketcombinationhasnotbeenreducedbyanyphysicaldamagetoeither.

•

•

•


Fig. 10

1�


1�

Before refitting any plug and socket, checkthat the mating electrical connections arenot damaged, misaligned or elongated (seeFig. 11) and have no contamination presentwhichmightcauseashortcircuit.

When testing a pressure modulator valve, ifanexternalvoltageisappliedtothesolenoidsthis should not exceed 17 Volts for a valveratedat12Voltsor33.5Voltsforavalveratedat24Volts. Theappliedvoltageshouldnotbeleftinplaceformorethanafewseconds.Prolonged application of an external supplywill result inoverheatinganddamage to theinsulationofthesolenoid.

On the completion of any work on the ABSensure that the complete braking system istestedbeforethevehicleisusedonthepublichighway.

1.3.3 DosandDon’tsforABS pneumaticcomponents andpipework

Beforecommencingworkonavehicle,alwayschockthewheelstopreventthevehiclerollingwhenthebrakesarereleased.

Never connect or disconnect a hose or linecontaining air pressure, it may whip as airescapes.Neverremoveadeviceorpipeplugunlessyouaresure thatallsystempressurehasbeendepleted.

If anymodificationsaremade to the vehiclethatrequireanyincreaseinthe lengthofthepipework between the pressure modulatorvalves and the service brake actuators thenany increase must be kept to a minimum.Any additional piping must have an internaldiameterofatleast10mm.90oelbowfittingsmustnotbeused.Theremustbenokinksinthepipeworkandthepipingmusthaveasmoothflowunderallconditionsofsuspensiontravelandsteeringmovement.

•

•

•

•

•

•


When screwing a fitting or brake hose intoa valve, ensure that the threads are cleanand undamaged and do not exceed therecommendedtighteningtorque(seeSection2.7onVossfittings).

On the completion of any work on the ABSensure that the complete brake system istestedbeforethevehicleisusedonthepublichighway.

•

•

Fig. 11

1�1�


1.4 Troubleshootingand Fault-finding

1.4.1 NormalOperation

Ifthesystemisworkingnormallyandtherearenofaults then,when the ignition isswitchedon, theABSwarninglamponthedashboardwillilluminateand thengoout. Itwillnot illuminateagainwhiletheignitionremainsswitchedonunlessthereisaproblemwiththesystem.

1.4.2 Start-upCheck

The Electronic Control Unit (ECU) used in theABS6 system contains two interconnectedmicroprocessors. Each microprocessor checksthe function of the other and in the event of amalfunction the faulty microprocessor will beshut down with the remaining microprocessorcontinuingtoprovidetheABSfunction.TheECUalsohas theability tocheck theoperationof theothercomponentsinthesystemandtheintegrityofthesystemcabling.WhentheABS6systemisfirstswitchedontheABSwarninglampisswitchedon for2secondsby theECUwhile itcarriesouta ‘static’ check of the system components andcabling. This start-up check also shows that theABSwarninglampisoperatingcorrectly.IftheABSwarninglampdoesnotilluminatewhenthesystemis first switched on, the bulb and the electricalsupplytotheECUshouldbechecked.

1.4.3 FaultDetection

Once the static check is complete, providing nofaultwasfound,theABSwarninglampisswitchedoff. Should the ECU detect any malfunction orproblemduring thestaticcheck then itwill leavethe ABS warning lamp switched on and shutdown,eitherpartiallyorcompletely,theoperationof theABS. If theECUhaddetecteda faultwithanywheelspeedsensorwhenitwaslastpoweredup,thentheECUwillleavetheABSwarninglampswitchedonuntilthevehicleisdrivenandtheECUcandetectacceptablesignalsfromallwheelspeed

sensors.WhenacceptablesignalsaredetectedtheECUwillswitchofftheABSwarninglamp.

The ECU continuously monitors the condition oftheABScomponentswhile thevehicle is inuse.If the ECU detects any malfunction or problem(eitherwith thebrakes releasedorapplied) itwillswitchontheABSwarninglampandshutdown,eitherpartiallyorcompletely,theoperationoftheABS.

OncetheABSwarninglamphasbeenswitchedontosignifythatafaultexistsinthesystemthenatureandlocationofthefaultmustbeidentifiedassoonaspossiblebyoneoftwomethods:

UseoftheBlinkCodes

UseofPCDiagnostics

Thevehicleshouldbedriventothenearestservicecentreforcorrectionofthefault.

1.4.4 UsingBlinkCodes

TheABSwarningLampisusednotonlytodisplaythefactthatafaultexistsbutalsotodisplayblinkcodes.

The blink code function within the ECU can beusedtodisplaytwotypesofblinkcode:

ConfigurationBlinkCodesshowingthesystemconfigurationoftheECUprogramming.

FaultBlinkCodesgivinginformationonfaultsdetectedandstoredbytheECU.

Blink codes are triggered by operating the blinkcode switch, which is located in the vehicle’selectrical compartment and the codes will bedisplayedbyshortperiodsofillumination(‘blinks’)of theABSwarning lampon thedashboard.Thenumberof ‘blinks’ iscountedand theblinkcodecan be interpreted from tables below. The blinkcodeswitchisusedinthefollowingmanner:

•

•

•

•

1�


1�

In the followingdescriptions theoperationof theblinkcodeswitchandtheilluminationoftheABSwarninglampareshowndiagrammatically.

Operation of the Blink Code Switch

Theconditionoftheblinkcodeswitchisrepresentedby a step in a graph with time as its base (seeFig.12).

TheblinkcodedisplayedbytheABSwarninglampis represented in twoways.Firstly,withapairofsymbols,onerepresenting the lamp ‘off’and theotherrepresentingthelamp‘on’(illuminated)andsecondlybyastepinagraphwithtimeasitsbase(seeFig.13).

Note:

TheABSwarninglampwillilluminatetoshowthattheblinkcodeswitchispressed.

Fig. 12

Fig. 13


1.4.5 ConfigurationBlinkCodes

WiththeECUpowered(ignitionswitchedon)wait at least 1 second, then press the blinkcode switch twice in quick succession andrelease.Thetransmissionoftheconfigurationblinkcodeistriggered.

The blink code will be displayed as shortilluminations (blinks) of the ABS warninglamp.

The blink code is divided into two blocks,each block comprising two numbers. Foreach number the series of ‘blinks’ will beapproximatelyhalfasecond longwithhalfasecondpausebetweenthem.

Countthefirstseriesofblinkstoestablishthe1stNumberand,afterapauseofapproximately1.5seconds,asecondseriesofblinksshould

•

•

•

•

becountedtogivethe2ndNumberofthefirstblock(seeFig.14).

After another pause of approximately4 seconds a third series of blinks shouldbe counted to give the 1st Number of thesecond block. There will then be a pauseof approximately 1.5 seconds after which afourth series of blinks should be counted togivethe2ndNumberofthesecondblock(seeFig.14).

Using the chart on the following page theconfigurationoftheECUcanbeestablished.

The transmission of the configuration codecanbeterminatedatanytimebypressingtheblinkcodeswitchagain.

•

•

•

2020

Fig. 14

Configuration Sequence

Configuration Blink Codes

Block Number Blinks Configuration1 1st 1 12Volt

2 24Volt

2nd 2 4S/4M

15 Invalidconfiguration

2 1st 1

2

3

4

J1939CANlinkandendurancebrakingsystem(exhaustbrake/retarder)relaynotfitted.

J1939 CAN link fitted, endurancebraking system (exhaust brake /retarder)relaynotfitted.

J1939 CAN link not fitted, endurancebraking system (exhaust brake /retarder)relayfitted.

J1939CANlinkandendurancebrakingsystem(exhaustbrake/retarder)relayfitted.

2nd 2 TractionControlnotinstalled

Note:

WiththeABS6Standardsystemtherearenoextrafeaturesandsoonlytheaboveconfigurationblinkcodes should be displayed. If any other codes


aredisplayedandthecorrectECUisfittedtothevehiclethencontactyournearestservicecentreassoonaspossible.

21


21

1.4.6 FaultBlinkCodes

With the ECU powered (‘ignition on’), waitat least 1 second then press the blink codeswitchonceandrelease.Thetransmissionofthefaultblinkcodeistriggered.

The blink code will be displayed as shortilluminations (blinks) of the ABS warninglamp.

The blink code for a fault is split into twoseries of ‘blinks’ - the first series of blinks(approximately0.5secondseach) shouldbecounted to give a “1st Number” and, aftera pause of approximately 1.5 seconds, asecond series of blinks (approximately 0.5seconds each) should be counted to give a“2ndNumber” (seeFig.15).Using thechartsonthefollowingpages,itispossibletoidentifythecomponentand its fault. If there ismorethan one fault, the next blink code will startapproximately4secondslater.

TheABSECUisabletostorespecificcodesforeveryfaultdetected.Thememorycanstoreamaximumof16faults.

•

•

•

•

Faultcodesforfailuresthataremostrecentlydetected are displayed first and oldestdetectedfaultsaredisplayedlast.

Theblinkcodesequence,i.e.oneblinkcodeper fault, can be repeated by pressing theblink code switch again at the end of thesequence.Notethatpressingtheblinkcodeswitchduringthesequencewillterminatethetransmissionoftheblinkcodes.

During output of the blink codes, normaloperationoftheECUisdisabled(i.e.noABSfunction).

•

•

•

Fig. 15

Fault code sequence


2222

Fault Blink Codes

1st Number 2nd Number Fault Description

1

2

2

2

2

2

2

3

3

3

3

3

3

4

4

4

4

4

1

1

2

3

4

5

6

1

2

3

4

5

6

1

2

3

4

5

NofaultsrecordedbytheECU.

Airgaptoobig(seeSection2.4forguidance).

Missingspeedsensorsignalatdriveoff,(seeSection2.4forguidance).

Damaged/contaminated tooth on sensing ring, erratic signal from speed sensor,checksensingringalignmentandwheelbearingadjustment(seeSections2.3and2.4forguidance).

Unstablesignalfromspeedsensor,checksensingringalignmentandwheelbearingadjustment,checkwiringforpossiblesourceofinterference(seeSections2.3and2.4forguidance).

Lossofspeedsensorsignal(seeSection2.4forguidance).

Sensorwiresshortedorbroken(seeSection2.4forguidanceandSection3forX2Pluglayout).



Damaged/contaminated tooth on sensing ring, erratic signal from speed sensor,checkSensingringalignmentandwheelbearingadjustment(seeSections2.3and2.4forguidance).


Lossofspeedsensorsignal,(seeSection2.4forguidance).

Sensorwiresshortedorbroken,(seeSection2.4forguidanceandSection3forX2Pluglayout).



Damaged/contaminatedtoothonSensingRing,erraticsignalfromspeedsensor,checkSensingRingalignmentandwheelbearingadjustment(seeSections2.3and2.4forguidance).

Unstable signal from speed sensor, check Sensing Ring alignment and wheelbearingadjustment,checkwiringforpossiblesourceofinterference(seeSections2.3and2.4forguidance).



Wheel speed sensor, front axle, left side

Wheel speed sensor, front axle, right side

Wheel speed sensor, rear axle, left side

No fault found

2�


2�


4

5

5

5

5

5

5

8

8

8

8

8

8

8

8

9

9

9

9

6

1

2

3

4

5

6

1

2

3

4

5

6

7

8

1

2

3

4




Damaged/contaminated tooth on sensing ring, erratic signal from speed sensor,checksensingringalignmentandwheelbearingadjustment(seeSections2.3and2.4forguidance).




Releasesolenoid–shortedtobattery(seeSection2.6forguidanceandSection3forX2Pluglayout).

Releasesolenoid-shortedtoground(seeSection2.6forguidanceandSection3forX2Pluglayout).

Releasesolenoidwirebroken(seeSection2.6forguidanceandSection3forX2Pluglayout).

Valvegroundwirebroken(seeSection2.6forguidanceandSection3forX2Pluglayout).

Holdsolenoid–shortedtobattery(seeSection2.6forguidanceandSection3forX2Pluglayout).

Holdsolenoid–shortedtoground(seeSection2.6forguidanceandSection3forX2Pluglayout).

Holdsolenoidwirebroken(seeSection2.6forguidanceandSection3forX2Pluglayout).

System configuration error, check valve and system wiring and check ECUconfiguration(seeSection1.4.5).






Wheel speed sensor, rear axle, right side

Pressure modulator valve, front axle, left side

Pressure modulator valve, front axle, right side

Wheel speed sensor, rear axle, left side (continued)

2�2�



9

9

9

9

10

10

10

10

10

10

10

10

10

10

11

11

11

5

6

7

8

1

2

3

4

5

6

7

8

10

11

1

2

3













Shortedtobattery,removeX2PlugfromECUandcheckforvoltageonvalvegroundconnections,replacewiringifnecessary(seeSection2.6forguidanceandSection3forX2Pluglayout.

ShortedtogroundnotthroughECUorinternalvalvedefect,removeX2Plugandcheck resistance between valve ground connections and chassis ground (seeSection2.6forguidanceandSection3forX2Pluglayout).



ReleaseSolenoidwirebroken(seeSection2.6forguidanceandSection3forX2Pluglayout).

Pressure modulator valve, rear axle, left side

Pressure modulator valve, valve common ground

Pressure modulator valve, rear axle, right side

Pressure modulator valve, front axle, right side (continued)

2�


2�


11

11

11

11

11

15

15

15

15

15

15

15

15

15

15

15

16

16

16

16

4

5

6

7

8

1

2

3

4

5

6

7

9

10

11

15

1

2

3

4



HoldSolenoid–shortedtoground(seeSection2.6forguidanceandSection3forX2Pluglayout).

HoldSolenoidwirebroken(seeSection2.6forguidanceandSection3forX2Pluglayout).


Internalmicroprocessor fault, erase faultmemory (seeSection1.4.7), if this faultcodeisstillpresentthenreplacetheECU


ECU data error, erase fault memory (see Section 1.4.7), if this fault code is stillpresentthenreplacetheECU

ECUnotprogrammable,erasefaultmemory(seeSection1.4.7),ifthisfaultcodeisstillpresentthenreplacetheECU




Invalid configuration in ECU, erase fault memory (see Section 1.4.7), if this faultcodeisstillpresentthenreplacetheECU

Internalrelaynotswitching,erasefaultmemory(seeSection1.4.7),ifthisfaultcodeisstillpresentthenreplacetheECU

Internalrelaypermanentlyswitchedon,erasefaultmemory(seeSection1.4.7), ifthisfaultcodeisstillpresentthenreplacetheECU

ABSsoftwarenotcompatiblewithhardware,checksystem installationandECUconfiguration

Batterysupply–temporaryovervoltage,checkalternator/voltageregulator

Battery supply – temporary low voltage/low voltage during ABS control, checkconditionofbatteryandterminals

Batterysupply–brokenwire

Supplyvoltage–powerlinenoise/temporarypowerlinenoise


ECU internal failures

Power supply

Pressure modulator valve, rear axle, right side (continued)

2�2�



16

16

16

17

17

17

17

17

17

18

18

9

10

11

1

2

5

10

12

13

3

4

Ignitionsupply–temporaryovervoltage,checkalternator/voltageregulator

Ignitionsupply–temporarylowvoltage,checkconditionofbatteryandterminals

Ignitionsupply – lowvoltageduringABScontrol, check forcorrosiononbatteryterminals.

Relay controlling endurance braking device shorted to battery, check wiring toendurancebrakingdevice.

Relaycontrollingendurancebrakingdeviceshortedtogroundorbrokenwire,checkwiringtoendurancebrakingdevice.

Front to rear out of range, check that correct tyre sizes are fitted and that tyrepressuresarecorrect.

Warning lampgroundshorted tobatteryorbrokenwire,orwarning lampsupplyshortedtogroundorbrokenwire,checkwarninglampwiring(seeSection3forX1Pluglayout).

Wheelspeedsensorfailureinprevious‘poweron’cycle(willbedisplayedonlyafterawheelspeedsensorfaulthasbeenclearedfromtheECUmemory).Drivevehicleto20km/hr,ifABSwarninglampgoesoffthenproblemisfixed,iflampstaysonthenstopvehicleandcheckthefaultblinkcodesagain.

Wheelspeedsensorsincorrectlywired(lefttoright)onfrontaxleorrearaxle,checkwiringofX1andX2plugs(seeSection3forX1andX2Pluglayouts).

CAN-Busoff,checkCAN-Busconnectionsandterminatingresistor.

TimeoutorinvaliddataonERC1,checkCAN-BusconnectionsandtheECUwhichisgeneratingtheERC1message.

Warning lamp

Wheel Speed Sensors

Tyre size alignment

Endurance Braking Device (Engine Exhaust Brake or Drive Line Retarder)

J1939 CAN Data Link

Power Supply (continued)

2�


2�

1.4.7 ErasingFaultCodesfromtheECU memory

To erase all fault codes from the memory of theECU:

Pressandholdtheblinkcodeswitch.

Switchontheignition.

After approximately 3 seconds release theblinkcodeswitch.

Notes

The ABS warning lamp will illuminate whentheblinkcodeswitchispressediftheignitionisalreadyswitchedon. InthiscasetheECUmemorywillnotbeerased.

If any of the faults erased from the ECUmemorywererelatedtowheelspeedsensorsthen the ABS warning lamp will illuminateonthenextpowerupofthesystemandwillstayilluminateduntilthevehicleisdriventoaspeedofapproximately20km/hr.Oncedriventothisspeed,providingtheECUdetectsgoodsignalsfromtherelevantwheelspeedsensors,theECUwillswitchofftheABSwarninglamp(seeSection1.4.3).

1.4.8 PCDiagnostics

A computer based program ECUtalk® - ABSDiagnostics is available and provides severalfunctions:

Assists workshop diagnosis of ABSproblems.

Enables system check after servicing of theABSsystem.

Includes a database to enable storage andretrieval of information relating to customer,vehicleandtestresults.

•

•

•

•

•

•

•

•


Knowledge base covering the function andservicing advice for ABS systems and theircomponents,wiringdiagramsandasoftwaremanualfortheprogram.

WorkshopDiagnosticTesting

This section of the program leads the operatorthrough step-by-step testing of the ABScomponents,instructinghimateachstagehowtocarryoutchecksandtakemeasurements.Attheendofthetestafullreportcanbeprintedoutfromtheprogramandtheresultscanbestoredinthedatabaseforsubsequentretrieval.

EndofLine(EOL)Testing

This section of the program provides a guidedsemi-automaticprocessfortestingtheABSsystemanditscomponentsfollowinganyservicingofthesystem.Attheendofthetestafullreportcanbeprintedoutfromtheprogramandtheresultscanbestoredinthedatabaseforsubsequentretrieval.

DatabaseManagement

The database section of the program providesthe facility to store records of the workshop’scustomers,thecustomers’vehiclesandtheresultsofanyWorkshopDiagnosticorEOLtestscarriedoutonthosevehicles.

Theprogramhasauser-friendly interface for theaddition and maintenance of the records heldwithinthedatabase.

For more details on this program seeProduct Information Y032175-EN-000 “ABSDiagnostics” Diagnostics andDatabase ProgramforABS6Standard.

•

2�2�

2.SystemComponents

2.1 ElectronicControlUnit(ECU)

TheElectronicControlUnit(ECU)shouldbefoundmounted inaprotectedenvironment (in thecab)as it is not weatherproofed and it also needs tobemountedwhereitwillnotbesubjectedtoanyelectromagnetic radiation. The ECU should besupplied with power through a circuit breaker orfuseandthewiringtotheECUshouldbearrangedsothatthereisnopossibilityofwaterrunningalongthecablesintotheECU.

The ECU used in the ABS6 system containstwo interconnected microprocessors. The‘control’ microprocessor controls the ABSfunction of the system and the ‘monitoring’microprocessorcontinuouslychecks the functionofthe‘control’microprocessor.Ifthe‘monitoring’microprocessor detects a malfunction of the‘control’microprocessor,itwillswitchontheABSwarninglampandshutdowntheABSfunctionofthesystem.

The ECU is the ‘brains’ of the ABS. It receivesthe input data from the wheel speed sensors,processes the information and during a servicebrake application it decides upon any actionnecessary.HavingmadesuchadecisiontheECUwillinstructtherelevantpressuremodulatorvalvetotaketheappropriateactionandwillthenmonitortheaffectofthisactionandmakeanycorrectionsnecessary.

In addition to carrying out its functions during abrakeapplication,theECUmonitorstheconditionofthesystemcomponentsinitiallywhenthesystemisfirstpoweredupandthencontinuouslyaslongasthesystemispowered:

When the system is first powered up theECU switches on the ABS warning lamp onthe vehicle dashboard to demonstrate thatthebulbisfunctioningandthelampstaysonfor approximately 2 seconds while the ECUcarriesouta“static”testofthesystem.Duringthisstatic test theECUsendstestpulsestothewheelspeedsensorsandtoeachof thesolenoidsinthepressuremodulatorvalvestocheckelectricalcontinuityandtoensurethatthesolenoidsenergiseandde-energise.Ifthe

•

ECUfindsthatthesystempassesthisstatictestitwillturnofftheABSwarninglamp.Ifaproblemisfound,oriftherewasafaultrecordedbytheECUwhenitwaslastswitchedoff,theECUwillkeeptheABSwarninglampswitchedon to indicate that there is a problem thatneedsattention.IfawheelspeedsensorfaultwaspresentwhentheECUwaslastswitchedoffandithassincebeencorrected,theABSwarning lamp will remain switched on. Thelampwillstayonuntilthevehicleisdriventoaspeedofapproximately20km/hrandtheECUhas established that there is an acceptablesignalbeingreceivedfromthatsensor.Oncethe presence of an acceptable signal hasbeenestablishedtheECUwillswitchoff thelamp (see Section 1.4 “Troubleshooting andFault-finding”).

Following the static test, even when thereis no brake application made, the ECU willcontinuetomonitortheelectricalcontinuityinallcircuitsoftheABSusingtestpulsesaswellascheckingthequalityofthesignalfromthewheelspeedsensors.IfaproblemisdetectedthentheECUwillshutdowntheABS,eitherpartially or totally, and switch on the ABSwarninglamptoindicatethatafaulthasbeenfound(seeSection1.4“TroubleshootingandFault-finding”).

OnceafaulthasbeendetectedtheECUwillstoreinformationonthenatureofthefault,evenwhennotpowered,untilthefaultmemoryiserased(seeSection1.4“TroubleshootingandFault-finding”).

If a malfunction occurs in the ‘control’microprocessorof theECU then the ‘monitoring’microprocessor will switch on the ABS warninglampinthesamewayasotherfaultsareindicated.ECUsarenotserviceableandmustbereplacediffaulty.

•

2�


2�

2.2 ABSWarningLamp

TheABSwarning lampismounted inthevehicledashboardandisusedtosignalthepresenceofafaultwithanyoftheABScomponents.

When theABS ispowered (ignition switchedon)the ABS warning lamp should illuminate for 2secondswhiletheECUcarriesoutastatictestofthesystemand itshouldthengoout. If theABSwarninglampdoesnotilluminatewhentheignitionis first switched on, the condition of the bulbshould be checked immediately and it must bereplacediffoundtobefaulty.IfthebulbisfoundtobesatisfactorythencheckthepowersupplytotheECU.

IftheABSwarninglampfailstogoout,orifithasgone out after 2 seconds and then illuminatesagain,thisisanindicationofamalfunctionofthesystem. This should be investigated as soon aspossible (see Section 1.4 Troubleshooting andFault-finding).

2.SystemComponents

�0�0

2.3 SensingRingThesensingringisatoothedringrigidlymountedtotheaxleendsothatitrotateswiththewheel.

The sensing ring rotates relative to the wheelspeedsensor,whichinturnprovidesasinusoidalelectrical signal to the ECU. This signal can beusedtomeasuretherotationalspeedofthewheel(seeSection2.4“WheelSpeedSensor”).

For the wheel speed sensor to provide a goodsignaltotheECUit is importantthattheteethofthesensingringarecleanandingoodcondition.Ifthegapsbetweentheteethbecomefilledwithanymagneticmaterial, suchasweardebris from thebrakeitself,orifanyoftheteethbecomechipped(seeFig.16),thentheECUwillrecognisethatthesignalreceivedfromthewheelspeedsensorisofpoorquality (not truesinusoidal form).Whenthishappens the ECU will indicate a malfunction byswitchingontheABSwarninglampanditwillshutdown the ABS on the affected axle. If the gapsbetween the teeth have become filled then thedebrisshouldberemovedcarefullyensuringthatthecleaningprocessdoesnotdamagetheteeth.Iftheteethoftheringbecomedamagedorcorrodedthenthesensingringmustbereplaced.

Forthewheelspeedsensortoproduceaconsistentsinusoidaloutputitisessentialthatthesensingringrotatesparalleltothefaceofthesensor,therefore,maintaining the wheel bearing adjustment to themanufacturer’s specification is vital. In all casesthe run-out of the sensing ring must not exceed0.2mm.

Following the correction of any fault associatedwithasensingringtheECUfaultmemoryshouldbecleared(seeSection1.4.7).

2.SystemComponents

Fig. 16

�1


�1

2.SystemComponents

2.4 WheelSpeedSensor

The wheel speed sensor is mounted, using aspring-loaded bush, in a housing on the axle insuch a position that the end of the sensor is ascloseaspossibletotheteethofthesensingring.The wheel speed sensor contains an internalpermanentmagnetwhosemagneticfieldextendsashortdistancebeyondtheendofthesensorcase.Acoiliswrappedaroundasoftironcore,whichisattachedtothemagnet.Thiscoilisconnectedtotheoutputcable.

Fig. 17

Whenawheelrotates,theteethofthesensingringpassinturnthroughthemagneticfieldofthesensormagnet anddisturb the field therebycreatinganinducedvoltageinthesensorcoil.Thisvoltageismonitored by the ECU via the output cable. Thevoltagegenerated takes the formofasinewavewithboththevoltageandfrequencyincreasingastherotationalspeedofthewheelincreases(seeFig.17).TheECUrequiresaminimumvoltagebeforeitrecognisesthesignalfromthewheelspeedsensorandthereafteritusesthefrequencyofthesignaltomonitortherotationalspeedofthewheel.

The voltage generated by the coil is dependentnotonlyontherotationalspeedofthewheelbutalso on the gap between the end of the wheelspeed sensor and the teeth of the sensing ring:thelargerthegapthelowerthegeneratedvoltage.It is important, therefore, that thegap is keptassmallaspossibletoensurethatsufficientvoltageis generated to allow the ECU to recognise thesignal.

Undernormalconditionsthisgapshouldresultina generated voltage of >100mV at 5km/h (seeFig.18).

Note:

If a rolling road is not available then a speed ofapproximately5km/hcanbesimulatedbyjackingupawheelandrotatingitbyhandataspeedof1revolutionevery2seconds(0.5rev/sec).

The quality of the sine wave generated by thewheelspeedsensor is importantandthiscanbedegradedbydamage to the teethof thesensingring.Damage,suchas‘chipped’teethcancauseanunstablesignal tobegeneratedby thewheelspeed sensor which will not be accepted by theECU. Should this occur the ECU will switch onthe ABS warning lamp and shut down the ABSfunction. Similarly, ‘brake squeal’ can cause anunstablesignalfromthewheelspeedsensorwithpossiblythesameresult.

Wheel Speed Sensor output signal

�2�2

The spring-loaded sensor bush is used to holdthe wheel speed sensor whilst allowing easyadjustment of the gap between it and the teethofthesensingring.Thewheelspeedsensorcanslideinthesensorbush,sothegapbetweenthewheelspeedsensorandtheteethofthesensingring can be set by manually pushing the sensorgentlyintocontactwiththeteethandthenturningthewheelbyhand.Afterpushingthewheelspeedsensorintocontactwiththesensingring,withthesystemnotpoweredup(i.e.ignitionisturnedoff),thewheelshouldberotatedbyhand.Anyrun-outof thewheelbearingswill cause the teethof thesensingringtopushawaythewheelspeedsensortherebysettingtheairgapbetweenthetwoparts.

The wheel speed sensor and its extension cablecanbecheckedasfollows:

Consult the wiring diagrams in Section 3 toestablish which plug (X1 or X2) and whichconnectorsareconnectedtothewheelspeedsensor/sensorextensioncabletobetested.

Connectamultimeter(settoreadACvoltage)to the appropriate contacts of the plug (seeexampleinFig.19).

Rotate the relevant vehicle wheel atapproximately1revolutionevery2seconds.

If the gap between the wheel speed sensorand the sensing ring is set correctly, themultimetershouldshowageneratedvoltageofatleast0.1Volts(100mV)AC.

Theresistanceofthesensorcoilcanalsobecheckedwhilethemultimeterisconnectedtotheplug.Thecoilshouldhavearesistanceof1750+/-175Ohms.

If a problem is found with either of thesereadings,disconnectthewheelspeedsensorfrom the sensor extension cable and repeatthe measurements having connected themultimeter to the connector on the sensoroutputcable (seeFig.20).Thiswillestablishwhether the problem lies with the sensor ortheextensioncable.

•

•

•

•

•

•

2.SystemComponents

Fig. 20

Fig. 19

NOTE:thecorrectcontacts

for testing should be

established fromSection3

WiringDiagrams.

Fig. 18

��


��

2.SystemComponents

Ifawheelspeedsensororsensorextensioncableisfoundtobefaultythenitmustbereplaced.

Whenremovingawheelspeedsensordonotpullonitscable.

When replacing a wheel speed sensor the boreof thehousingshouldbecleaned, anewsensorbushshouldalsobefittedandthesensorshouldbegreasedwiththespeciallubricantprovided.

Whenfittingthesensoritshouldbepushedgentlyintocontactwiththeteethofthesensingringandthe vehicle wheel should be rotated by hand tosetthecorrectgap.Ifthesensordoesnotslideinthebushundermanualpressurethenthehousingshouldbe inspectedfordamage.Donotattempttoadjustthegapbymovingthesensingring.

If cable tiesareused tosecure theoutputcablefromthewheelspeedsensortheyshouldneverbeplacedclosetothesensorandtheyshouldneverby tightened excessively as the insulation of thecable can become crushed and a short circuitcouldresult.

Following the correction of any fault associatedwithawheelspeedsensortheECUfaultmemoryshouldbecleared(seeSection1.4.7).

Ifawheelspeedsensorfaulthasbeencorrectedas a result of theABSwarning lamp illuminatingthen, after the ECU fault memory has beencleared,whenthesystemisnextpoweredup,theABSwarninglampwillagainilluminate.Itwillstayilluminateduntilthevehicleisdriventoaspeedofapproximately20km/h.Oncedriventothisspeed,providingtheECUdetectsagoodsignalfromthewheel speed sensor, the ECU will switch off theABSwarninglamp.

Ifavehiclehasbeenputbackintoservicefollowingcorrection of a fault caused by too large a gapbetweenthewheelspeedsensorandthesensingringthen,withinafewdaysofoperation,thesamesensor fault re-occurs this is likely to be due toexcessiverun-outofthewheelbearingorincorrectfittingof thesensing ring. If thewheelbearing isfaulty then itshouldbeservicedandadjusted towithinthevehiclemanufacturer’sspecification.Inallcasestherun-outofthesensingringmustnotexceed0.2mm.

��

2.5 SensorExtensionCable

ThesensorextensioncableisusedtoconnectthewheelspeedsensortotheECU.Theconnectoronthewheelspeedsensoroutputcableisdesignedtojoinwiththesensorextensioncableandprovideaweatherproofseal. It isthereforeimportantthattheconnectorsareinsertedcorrectlyandarefullyengaged.

SeeSection2.4fordetailsconcerningthetestingofthewheelspeedsensorandextensioncable.

If a sensor extension cable is replaced and it issecuredwithcabletiesthentheyshouldneverbytightenedexcessivelyastheinsulationofthecablecan become crushed and a short circuit couldresult.

2.SystemComponents

��


��

2.6 PressureModulatorValve

The pressure modulator valve is rigidly mountedon the vehicle chassis as close as possible tothe brake actuator that it controls. The valve ispart of the service brake system, its inlet port(labelled ‘1’) is supplied with air pressure fromthe footvalvewhen thebrake isappliedand thedeliveryport(labelled‘2’)suppliesairpressuretotheservicebrakeactuator.BothportsaremachinedtotakeVossSystem230push-inpipefittings(seeSection2.7).Theelectricalcablesconnectingthepressuremodulatorvalveshouldalwaysberoutedsothatmoisturedoesnotrunalongthecablesintotheconnectoronthevalve.

The valve is connected electrically to the ECU,enablingittocontroltheoperationofthetwointernalsolenoids‘C’and‘D’(normallyde-energised).Thevalvehastwointernalnon-returnvalves‘A’and‘B’heldclosedbylightsprings(seeFig.21).

Fig. 21

Pressure Modulator Valve

2.SystemComponents

��

Description of the function of the pressuremodulator valve under ABS operation is givenbelow.ReferalsotoSection1.2.2.

Under normal braking operation, when thedrivermakesaservicebrakeapplication,airpressure flows from the foot valve into theinletport‘1’ofthepressuremodulatorvalve.Thisairpressurepushesopenthenon-returnvalve‘A’,andairflowsthroughthebodyofthevalveandthroughtheopensolenoid‘D’ontothespringsideofnon-returnvalve ‘B’holdingitclosed.Theairpressurealsoflowsout of the delivery port ‘2’ to the servicebrakeactuator(seeFig.22).Whenthedriverreleasestheservicebraketheairflowsbackfromtheservicebrakeactuatorthroughthepressuremodulatorvalveandoutoftheopenexhaustofthefootvalve.Ifarelayvalveorquickreleasevalveisfittedbetweenthefootvalveandthepressuremodulatorvalve theairwillexhaustthroughoneofthesevalvesinstead of flowing back to the foot valve.Whentheservicebrakeoperatesunderthesecircumstances the application and releaseare unaffected by the pressure modulatorvalve.Ifthepressuremodulatorvalvedeliveryisconnectedtoalargevolume(servicebrakeactuator of Type 30 or bigger) then, if the

1)

driver releases the foot valve rapidly, it isprobablethatthepressureonthespringsideofnon-returnvalve ‘B’will dropsufficientlyto allow the actuator pressure acting ontheothersidetoopenthenon-returnvalve.Underthesecircumstancesairpressurefromtheservicebrakeactuatorwillbeexhaustedthroughthepressuremodulatorexhaust.

DuringanapplicationoftheservicebrakeiftheECUdetectsfromthewheelspeedsensorsignalsthattheslipofoneofthewheelsstartsto increase and there is a rapid change indecelerationofthatwheel,i.e.itisindangerof locking, then the ECU will energise the‘Hold’ solenoid ‘C’ and ‘Release’ solenoid‘D’.Theenergisationof solenoid ‘C’allowsair pressure to flow to the spring side ofnon-returnvalve‘A’forcingittoclose.Whenthis happens the service brake actuatorbecomes effectively disconnected from thefootvalveandanyfurtherbuildupinpressurefromthefootvalvewillnotbetransferredtotheservicebrakeactuator.Theenergisationof solenoid ‘D’ exhausts the pressure onthe spring side of non-return valve ‘B’ andthe pressure on the other side pushes thevalveopenandallowstheairpressureintheactuatortoreducebyescapingthroughthe

2)

Fig. 22

Pressure Modulator Valve - normal service brake application

2.SystemComponents

��


��

2.SystemComponents

Fig. 23

Pressure Modulator Valve – service brake application – ‘Hold’ solenoid energised

exhaustofthepressuremodulatorvalve.(SeeFig.23).Theactionofreducingthepressurein the service brake actuator will generallypreventthewheelfromlocking.

Releasing the brake on the locked wheelallows whatever adhesion is availablebetweenthetyreandtheroadtorotateandspeedupthewheel.WhentheECUdetects

3)

fromthewheelspeedsignal that thewheelhas regained some rotational speed thentheECUwillpreventanyfurtherreductioninpressurebyde-energising thesolenoid ‘D’.Thiswillre-applypressuretothespringsideof non-return valve ‘B’ forcing it to close,therebyclosingtheconnectionbetweentheservice brake actuator and the exhaust of

Fig. 24

Pressure Modulator Valve – service brake application

– ‘Hold’ and ‘Release’ solenoids energised

��

2.SystemComponents

the pressure modulator valve. Solenoid ‘C’remainsenergisedandnon-returnvalve ‘A’remainsclosed(seeFig.24).

AsthewheelspeedcontinuestoincreasetheECUwillstarttoreapplythebrake.TheECUwillmomentarilyde-energise‘Hold’solenoid‘C’.Thiswillexhaustthepressureonthespringsideofnon-returnvalve‘A’allowingittoopenand increase the pressure inside the valveandintheservicebrakeactuator(seeFig.25).Themomentaryde-energisingof the ‘Hold’solenoid‘C’willcauseasmallstepincreasein pressure in the service brake actuator.When‘Hold’solenoid‘C’isre-energisedairpressurewillagainbeappliedtothespringsideofnon-returnvalve‘A’forcingitclosedand preventing any further pressure beingapplied to the service brake actuator. TheECU will continue to monitor the signalsfromthewheelspeedsensortoestablishtheaffectofthesteppedincreaseinpressureintheactuator.IftheECUdetectsthatthereisnotendencyforthewheeltolock,thenitwillmomentarilyde-energisethe‘Hold’solenoid‘C’ again allowing another small steppedincrease in pressure in the service brake

4)

actuator. The ECU will continue to monitorthesignalsfromallwheelspeedsensorstoestablishifthewheelthatwaslockedisstillspeedingupandifthisissoafurtherincreaseinpressureintheactuatorwillbepermitted.IfatanytimetheECUdetectsthatthewheelisshowingatendencytolockagainitwillrevertto step 2 above and repeat the processesaboveuntilthetendencyforthewheeltolockisnolongerpresentorthevehiclehasstopped.

Providingthatthereisnotendencytolock,theECUwillcontinuetoincreasethepressureintheservicebrakeactuatorinsmallstepsuntilthepressurereachesthelevelofthepressuredeliveredby the foot valveor thespeedofthewheelthatwaslockedreachesthesamespeedastheotherwheelsonthevehicle.Ifthewheel thatwas lockedstill hasa lowerlevelofadhesionthantheotherwheelsthenthelevelofbrakingsustainablebythatwheelwillbelessthanthosewiththehigherlevelofadhesion.SothelevelofpressureappliedbytheABStotheservicebrakeactuatoronthewheelwith lowadhesionwillbe lower thanthepressuredeliveredbythefootvalve,but

5)

Fig. 25

Pressure Modulator Valve – service brake application –

‘Release’ solenoid de-energised and ‘Hold’ solenoid de-energised momentarily

��


��

2.SystemComponents

willprovidethemaximumlevelofsustainableretardation for that wheel and the vehiclewhilstalsoprovidingvehiclestability.

The functionalityof thesolenoids in thepressuremodulator valves is checked by the ECU whenthe ABS is first powered (ignition switched on).Testpulses are sent to each solenoid aspart oftheECU’sstatic test tocheckthat theyenergiseand de-energise. This operation can be used asasimpletestforcheckingthepressuremodulatorvalves:

Start with the foot valve applied, the brakesystem pressurised and the ignition turnedoff.

Turn on the ignition to power the ABS anda short blast of air should be heard coming

•

•

fromtheexhaustofeachpressuremodulatorvalveastheECUsendsatestpulsetoeachsolenoidinturnaspartofthestaticcheck.

If a problem is suspected with a pressuremodulatorvalvethentheresistanceofthesolenoidcoils should be checked with a multimeter (seeFig. 26). The resistance of each coil relative togroundshouldbebetween4.7and5.7Ohmsfora12Voltsystemandbetween12and19Ohmsfora24Voltsystem. If the resistanceof thecoils iscorrectthencheckthewiringbetweenthepressuremodulatorvalveandtheECU.

DIN Bayonet Connector

Ground(common)

ReleaseSolenoid

HoldSolenoid

M24x1 Connector

Fig. 26

�0�0

If an external voltage is applied to a solenoid ofa pressure modulator valve in order to check itsfunction then this should not exceed 17 Voltsforavalve ratedat12Voltsand33.5Volts foravalveratedat24Volts.Theappliedvoltageshouldnotbeleft inplaceformorethanafewseconds.Prolongedapplicationofanexternalsupplytothesolenoidwillresult inoverheatinganddamagetotheinsulationofthesolenoid.

DuringtheoperationoftheABSfunctionitisvitalthatthepressuremodulatorvalveisabletoexhaustthe air pressure in the service brake actuator asquicklyaspossibleandsotheunrestrictedflowofairthroughtheexhaustofthepressuremodulatorvalveisessential.Theexhaustflapofthepressuremodulator valve should be checked at regularserviceintervalstoensurethatitisnotbecomingblocked by the accumulation of contaminationthrown up by road wheels. If the exhaust of thevalveshouldbecomeblocked,evenpartially,thenwhentheservicebrakehasbeenreleasedthereisapossibilityoftheblockagecausingpressuretoberetainedinthevalvebody,whichinturncouldcause

asmallamountofairpressuretoberetainedintheservicebrakeactuator.Thisretainedpressuremay,insomecases,besufficienttocausethebrakesto‘drag’(seeFig.27).Ifthissituationisfoundthentheexhaustflapandexhaustpassagewayshouldbe cleaned taking care that no contaminationentersthevalve.

Ifthereisanyproblemwithapressuremodulatorvalve,apartfromblockageoftheexhaust,thenthevalvemustbereplaced,asitisanon-serviceableitem. When replacing a pressure modulatorvalveensure that thepipefittingsare installed inaccordancewiththeSection2.7onVossfittings,payingparticularattentiontothetighteningtorques.Thereisnoneedtousethreadsealantofanytypeonthesefittings.

Following the correction of any fault associatedwith a pressure modulator valve the ECU faultmemoryshouldbecleared(seeSection1.4.7).

Fig. 27

Pressure Modulator Valve – service brake released – ‘Release’ and ‘Hold’ solenoids de-energised – exhaust

partially blocked holding a low pressure in the modulator body causing pressure to be

trapped in the brake chamber.

2.SystemComponents

�1


�1

2.7 VOSSplugconnectionsystem230(assemblyinstructions)

The VOSS plug connection system 230 permitstherapidfittingofnylontubes;onlyaspanner isneededtoundotheconnector.Itconsistsoffourcomponents(seeFig.28):plugwithfir-tree(2),malefitting(4),retainingclip(8)andspringelement(9).Theplughasawideholdinggroove,inwhichtheretainingclip(8)engagesonassembly.TwoothergroovesaccommodateO-rings.ThefirstO-ring(5)sealstheconnectoragainsttheairpressure.ThesecondO-ring (3)prevents the ingressof foreignmatter.Atthesametime,theredcolourofO-ring(3) serves as a visual check to indicate correctassembly.

Themalefitting(4)isscrewedtightlyintothebodyof the device with the thread being sealed byO-ring(6).Theplasticretainingclip(8)isopenononesideandisopenedbythetaperedtailoftheplug during assembly. After insertion of the plugthisclipengagestheholdinggroove.Theretainingclipisself-centring.

The rubber springelement (9) is inserted into anannularspaceatthebaseoftheformedboreinthedevice.Thedesignof thespringelementcausestheplugtobeplacedunderaxialstressaftertheretainingclip(8)hasengaged.

Removal/refitting of a connector

IfadeviceusingtheVOSS230connectorsneedsto be changed, the connectors are removed byunscrewing the male fitting (4), noting the portnumber fromwhich it is removed.Theconnectorassemblyremainsattachedtothenylonpipe.

Fitanewspringelement (9) into theportsof thenewdevice.Fittheconnectorsintothesameportsonthenewdeviceaswereusedontheremoveddevice.Fullytightenthemalefitting(4)toatorqueof10+1Nm.

Shouldaconnectorassemblyneedtobereplacedfollowtheprocedurebelow:

Cutting the nylon tube to length

Thenylontubemustbecutoffsquare.Asawmustnotbeused for thispurposeas theunavoidableformationofburrsjeopardisesthesealingcapabilityof the connection. For cutting the nylon tube tolength,theVOSStubecuttingplierscanbeusedsothatthetubeiscutcleanlyandatrightangles.Reworking thecutsurface,suchasdeburring, isnotnecessary.

Pressing the fir-tree into the nylon tube

Thefollowingistobeobserved:

Do not remove the protective cap from theplug.

Thepressing-inprocedureistobeperformedatroomtemperature

Thenylontubemustnotbeheated

The fir-tree must not exhibit any damageotherwisetheconnectionwiththenylontubewillnotbetight

The fir-tree should be clean and free ofgrease

•

•

•

•

•

2.SystemComponents

1 Nylontube

2 Plugwithfir-tree

3 Dirtsealandvisualassemblycheck(redO-ring)

4 Malefitting

5 Plugseal(O-ring)

6 Threadseal(O-ring)

7 Productbody

8 Retainingclip

9 Springelement Fig. 28

�2�2

2.SystemComponents

Assembly of the male fitting using VOSS assembly mandrel (see Fig. 29)

Themalefitting(4)withgreasedO-ring(6),retainingclip (8) and spring element (9) are successivelymountedontotheassemblymandrel.Theassemblymandrel prepared in this way is screwed hand-tight into theconnectionbore in thedevice.Themandrel iswithdrawn, the individualcomponentsremainintheirposition.Themalefitting(4)isthentightenedfullytoatorqueof10+1Nm.

Assembly of the male fitting without using the assembly mandrel (see Fig.30)

Thespringelement(9)isinsertedintopositionunderthethreadrootoftheconnectionbore(diagramsaandb).

The retainingclip (8) is introducedso that itrestsflatonthethreadroot(diagramsbandc).Thespringelement(9)andretainingclip(8)mustbesymmetricallypositioned.

The male fitting (4), pre-assembled with thepre-greased O-ring (6), is then screwed byhand into the tappedbore (diagramc), thentightenedfullytoatorqueof10+1Nm.

Assembly of the plug with the male fitting

Remove the protective cap from the plug. Pushtheplug(withnylontubefitted)intothemalefittinguntiltheretainingringengagesinthegrooveoftheplug.TheredO-ring(3)shouldnotbevisible.Checkthattheretainingringhasengagedbypullingtheassemblyagainstthedirectionofinsertion.

Grease

UsegreaseII14525Fuchs“Renolit”HLT2.

•

•

•

Fig.29

Fig.30

��


��

3.WiringDiagrams

��

X1 PLUG LAYOUT

X2 PLUG LAYOUT

3.WiringDiagrams

Überschrift

S y s t e m s f o r C o m m e r c i a l V e h i c l e s

Knorr-Bremse Australia Pty. Ltd. Granville NSW 2142 Australia Tel: +61 1300 309-991

Knorr-Bremse GmbH Systeme für Nutzfahrzeuge2340 Mödling AustriaTel: +43 2236 409-436

Knorr-Bremse Benelux B.V.B.A2220 Heist-op-den-Berg Belgium Tel: +32 1525 7900

Knorr-Bremse GmbHSistemas para Veículos Comerciais Brasil LtdaSão Paulo - SP Cep : 04696-902 Brazil Tel: +55 11 5681 1104

Knorr-Bremse Far East Ltd. Truck Brake Systems Division Hong Kong China Tel: +852 2861 2669

Knorr-Bremse Brake Equipment (Shanghai) Co. Ltd. Truck Brake Systems DivisionShanghai, 200131 China Tel: +86 21 5046-0776

Knorr-Bremse Systemy pro uzitkova vozidla, CR, s.r.o. 463 62 Hejnice Czech Republic Tel: +420 482 363-611

Knorr-Bremse Systèmes pour Véhicules Utilitaires France S.A.14104 Lisieux Cedex France Tel: +33 2 3132 1200

Knorr-Bremse RUS 603029 Nischnij Novgorod Russian Federation Tel: +7 831 257-6661

Knorr-Bremse Systeme für Nutzfahrzeuge GmbH 119017 Moscow Russian Federation Tel: +7 095 234-4995

Knorr-Bremse S.A. Pty. Ltd. 1610 Kempton Park South Africa Tel: +27 11 961-7800

Bost Ibérica, S.L. 20303 Irun Spain Tel: +34 902 100-569

Knorr-Bremse System for Tunga Fordon AB200 11 Malmoe Sweden Tel: +46 40 680 5880

Knorr-Bremse Systeme für Nutzfahrzeuge GmbH8303 Bassersdorf Switzerland Tel: +41 44 888 77-55

Knorr-Bremse Systeme für Nutzfahrzeuge GmbH80040 Findikli - Istanbul Turkey Tel: +90 212 293-4742

Knorr-Bremse Systems for Commercial Vehicles Ltd. Bristol BS16 7FE United Kingdom Tel: +44 117 9846-100

Bendix Commercial Vehicle Systems LLCElyria, OH 44035 USA Tel: +1 440 329-9100

Knorr-Bremse Systeme für Nutzfahrzeuge GmbH 80809 Munich Germany Tel: +49 89 3547-0

Hasse & Wrede GmbH 12681 Berlin Germany Tel: +49 30 9392-3101

Knorr-Bremse Fékrendszerek Kft. 6000KecskemėtHungary Tel: +36 76 511 100

Knorr-Bremse Systems for Commercial Vehicles India Private Ltd. (Joint Venture of Knorr-Bremse Far East and Tata Autocomp Systems Ltd.)Pune 411 057 India Tel: +91 20 2293-9141-47

Knorr-Bremse Sistemi per Autoveicoli Commerciali S.p.A. 20043 Arcore Italy Tel: +39 039 6075-1

Knorr-Bremse Commercial Vehicle Systems Japan Ltd.Tokyo 171 0021 Japan Tel: +81 3 3971-8501

Knorr-Bremse Korea Ltd. Truck Brake Division Seoul 100-391 Korea Tel: +82 2 2273-1182

Knorr-Bremse Benelux B.V.B.A3641 SK Mydrecht Netherlands Tel: +31 297 239-330

Knorr-Bremse Systeme für Nutzfahrzeuge GmbH Moosacher Str. 8080809 Munich Germany Tel: +49 89 3547-0 Fax: +49 89 3547-2767

w w w . k n o r r - b r e m s e . c o m

Y0

2�

��

�-E

N-0

02

2

00

�Co

pyrig

ht 20

09 ©

Kno

rr-Br

emse

AG

- all r

ight

s res

erve

d, in

cludi

ng in

dustr

ial pr

oper

ty ri

ghts

appl

icatio

ns. K

norr-

Brem

se A

G re

tain

s any

powe

r of d

ispos

al, su

ch as

for c

opyin

g and

tran

sferri

ng.

product manual abs 6 standard anti-lock braking system katalogoi/auto/abs6y029757e002.pdfan...

Documents