Design and Function - Volkswagen Technical Site

Service.Self-Study Programme 231Euro On-Board Diagnostic SystemFor petrol enginesDesign and Function

IntroductionLegal frameworkOn 13th October 1998, the European Union passed the EU Directive 98/69/EC, according to which theintroduction of EOBD is mandatory for all member countries. This directive has been adopted intonational law in the Federal Republic of Germany.The introduction of EOBD is not directly coupled with an exhaust emission standard of the EuropeanUnion (EU II, EU III, EU IV) or the Federal Republic of Germany (D2, D3, D4). Therefore, the target datefor the introduction of OEBD and the associated transition period must be considered independently ofthe various exhaust emission standards.Target date for introduction of EOBDWith effect from the 1st January, 2000, the automobile industry will be required to perform only one typetest for new petrol-engined models if they have EOBD.Transition periodThe transition period pertains to models which have been type-tested prior to 31st December, 1999 andmeet the EU II, D3 or D4 exhaust emission standard. The buyer may still register these vehicles until31st December, 2000 and operate them without EOBD with no restrictions. With effect from this date,existing models will be required to have EOBD for initial registration purposes (buyer).The EOBD legislation does not affect vehicles which were registered by the buyer priorto 31st December, 1999.Type tests in the automobile industryNew modelswithout EOBDNew modelswith EOBDYear 2000 Year 2001New vehicleswithout EOBDNew vehicles without EOBD(with EU II, D3 or D4)New vehicleswith EOBDHomologation of new vehicles of buyers231_0024

Overview of EOBDThe visible elements of EOBD are the self-diagnosis fault warning lamp K83 and the diagnosis interfacein the passenger cabin. The engine control unit performs all other functions and diagnostic operationsautomatically. The driver does not notice the ongoing checks on the systems in his vehicle which arerelevant to exhaust emissions. This means that not much changes for the driver of a vehicle with EOBD,however service personnel will be required to familiarize themselves with new automotive technologiesand the associated procedures.Self-diagnosis fault warning lamp K83If a fault impairing exhaust gas quality occurs onboard the vehicle, the fault is saved to the faultmemory and the self-diagnosis fault warninglamp is activated.231_011EOBD stores the "on" period of the selfdiagnosisfault warning lamp (in termsof kilometres travelled).If there is a risk of catalyst damage due tomisfiring, the self-diagnosis fault warning lampflashes.Diagnosis interfaceStored EOBD data can be read out via thediagnosis interface. The fault codes arestandardised so that data can be acquired usingany Generic Scan Tool (OBD visual display unit).The diagnosis interface must be within easyreach of the driver's seat.231_012EOBD checks:- The electrical functions of all componentswhich are important for exhaust gas quality.- The functioning of all vehicle systems whichhave a bearing on exhaust gas quality(e.g. lambda probes, secondary air system).- The functioning of the catalyst.- For misfiring.- The CAN databus.- For trouble-free operation of the automatictransmission.5

IntroductionNew vehicle systemsBefore we describe the details of EOBD to you, it is worth mentioning the new vehicle systems. Since thepublication of the Self-Study Programme 175 "On-Board Diagnostics II in the New Beetle USA", severalvehicle systems monitored by EOBD have been improved.For functional descriptions of the vehicle systems which are not described in detail in thisSelf-Study programme, please refer to Self-Study Programme 175.The broadband lambda probe(LSU – Lambda Probe Universal) is a newgeneration of lambda probes that are deployedbefore the catalyst.The name reveals the goals that were set for thedevelopment of this probe. The lambda value isrepresented by near-linear rises in current, andno longer by an abruptly rising voltage curve(which is the case with the step type lambdaprobe). As a result, it is possible to measure thelambda value over a larger measurement area(broader band).The conventional finger probes(LSH – Lambda Probe Heating) orPlanar Lambda Probe (LSF – Lambda Probe Flat)are also known as step probes because of theirstep-like voltage curves.Broadband lambda probeΙrichmixtureλ≈1Current Ιleanmixture231_005LambdaA step type lambda probe is used for the probeafter the catalyst.The step-like measurement area of a step typelambda probe around the value lambda=1 (λ=1)is sufficient for the probe after the catalyst toperform its monitoring function.Step type lambda probeUrichmixtureleanmixtureλ≈1Voltage U231_004Lambda6

● FunctionThe broadband lambda probe acquires and evaluates lambda values differently to the step typelambda probe. Therefore, the lambda value is determined from a change of current, not from a changeof voltage. However, the physical processes are identical.To show the functional differences clearly, both systems are described briefly below.Step type lambda probeAmbient airExhaust gasElectrodesProbe voltagemVEngine control unitThe core of this probe is a ceramic body coatedon both sides (Nernst cell). These coatings act aselectrodes; one electrode layer is in contact withthe ambient air and the other is in contact withthe exhaust gas. The differential between theoxygen concentration in the ambient air and inthe exhaust gas results in a voltage between theelectrodes. This voltage is evaluated in theengine control unit in order to determine thelambda value.231_032Exhaust gasDiffusionductPump cellPump currentA450mVBroadband lambda probeThis probe also uses two electrodes to generate avoltage, which is the result of different oxygenconcentrations. The difference to the step typelambda probe is that the voltage of theelectrodes is kept constant. A pump cell(miniature pump) supplies the electrode on theexhaust side with enough oxygen to maintain aconstant voltage of 450 mV between the twoelectrodes. The engine control unit converts thepower consumption of the pump into a lambdavalue.Ambient airProbe voltageMeasurement area231_0337

Introduction● Examples showing how thebroadband lambda probe is controlledThe fuel/air mixture is becoming leaner. Thismeans that the oxygen content in the exhaust gasis rising and the pump cell, while operating at aconstant delivery rate, is pumping more oxygeninto the measurement space than can escapethrough the diffusion duct. As a result, theoxygen-to-ambient air ratio changes and thevoltage between the electrodes drops.A450mV231_036To restore the voltage between the electrodes to450 mV, the oxygen content must be reduced onthe exhaust side. To achieve this effect, the pumpcell must pump less oxygen into the measurementspace. The pump delivery rate, therefore, isreduced until the voltage is restored to 450 mV.The engine control unit converts the powerconsumption of the miniature pump into alambda control value and alters the mixturecomposition accordingly.A450mV231_0378

A450If the fuel/air mixture is too rich, the oxygencontent in the exhaust gas drops. As a result, thepump cell, while operating at a constant deliveryrate, is delivering less oxygen into the measuringarea and the voltage between the electrodes isrising.In this case, more oxygen is escaping through thediffusion duct than the pump cell can deliver.mV231_038AThe delivery rate of the pump cell must beincreased in order to increase the oxygen contentin the measuring area. As a result, the electrodevoltage is restored to 450 mV and the powerconsumption of the pump cell is converted into alambda control value by the engine control unit.450mV231_039The pump action of the pump cell is a purely physical process. No mechanical components areused for the function. The pump cell is represented above symbolically.A positive pump cell voltage attracts negative oxygen ions through the oxygen-permeableceramic material.The broadband lambda probe and the engine control unit are a single system. It is importantthat the lambda probe matches the engine control unit.9

Introduction● DesignSensor element in cross section5Pump cell with electrodesa4b1cd23231_0421 Nernst cell with electrodes2 Probe heater3 Ambient air duct4 Measurement space5 Diffusion ductabcdSymbolic representationElectrode (anode)Current sourceCeramic materialElectrode (cathode)Two makes of lambda probe are fitted.● Electrical circuit (NTK)● Electrical circuit (Bosch)J . . .J . . .G39G39231_052231_059● Effects of failure of probe before catalystIf the signal from the lambda probe fails, nolambda control takes place and lambdaadaption is disabled.The fuel tank purging system enters emergencyrunning mode.The secondary air and catalyst diagnoses aredisabled.The engine control unit uses a mapped control asan emergency function.The broadband lambda probe mayonly be replaced complete with cableand connectors.10

Electrical exhaust gas recirculation systemThe exhaust gas recirculation system is primarilyused to increase fuel efficiency in lowdisplacementengines.As a result of the recirculating exhaust gases, theengine is required to induce less air. The resultingsavings in suction work improve fuel efficiency.231_046Exhaust gas recirculation valve N18 (new version)● Function23Two valves were previously used to control theexhaust gas supply:- Exhaust gas recirculation valve N18- EGR valve14The EGR valve was activated electrically by theengine control unit and transferred acorresponding vacuum to the EGR valve.The vacuum caused the EGR valve to open,allowing exhaust gas to enter the intakemanifold.231_0471 Engine control unit J...2 Exhaust gas recirculation valve N183 EGR valve4 Catalyst11

IntroductionOnly one valve is still used for electrical exhaustgas recirculation:- Exhaust gas recirculation valve N18This valve is activated directly by the enginecontrol unit and electromagnetically adjusts theopening stroke for exhaust gas recirculation.The integrated exhaust gas recirculationpotentiometer signals the actual opening strokeof the valve to the engine control unit.41321 Engine control unit J...2 Exhaust gas recirculation valve N18 andexhaust gas recirculation potentiometer G2123 Vent4 Catalyst231_043The EGR valve and the exhaust gas recirculation valve are combined in the electrical exhaustgas recirculation system.● Electrical circuit● Effects of failure of valveJ . . .If the valve fails in the open position, the engineshuts down at idling speed and can no longer bestarted.If the valve remains closed, the failure has noeffects on vehicle operation.The fault will nevertheless be detected andsaved.N18G212+ +231_05612

Electric throttle driveThe throttle valve was previously adjusted mechanically by means of a Bowden cable. The throttle valvewas only actuated by electric motor when the engine was running at idling speed or when a cruisecontrol system was in use. Use of the electrical throttle control enables the engine control unit to adaptthe throttle valve position to the given basic conditions in any driving situation.● FunctionThe driver's preference or the signals from theaccelerator pedal module are transferred to theengine control unit. Making allowance for allauxiliarysignals, the engine control unit thendetermines how the torque requirement can bestbe implemented.The torque requirement is implemented via theelectromotively adjustable throttle valve, theignition system and the fuel injection system.Malfunctions are indicated via the electricthrottle control fault lamp.For example, auxiliary signals are supplied by:- The cruise control system,- The air conditioning system,- The idle speed control,- The lambda control,- The automatic transmission and- ABS/ESP.For detailed information regarding theelectric throttle drive, please refer toSelf-Study Programme 210.Auxiliary signalsAccelerator pedalmoduleThrottle valvecontrol unit J338Ignition,fuel injectionElectric throttle control faultlamp K132(EPC = Electronic Power Control)231_00813

IntroductionIntegrated shaft sealing ring sensorIn several engines, a new Generation of engine speed sender G28 is in use – the “Integrated shaftsealing ring sensor” (IWDS – Integrierter Wellendichtring-Sensor).The sender is mounted in a sealing flange for the crankshaft on the gearbox side of the engine.The sender wheel (60-2 teeth) is press-fitted on the crankshaft in a precisely defined position.The IWDS systems are made by two different manufacturers and, therefore, may differ in terms oftheir design.CrankshaftEngine speed sender G28Engine sideGearbox sideSender wheelSealing flange231_030Crankcase● Electrical circuit● Effects of failureJ . . .Maximum engine speed is reduced and theengine control unit calculates a default value forengine speed from the signal supplied byHall sender G40.G28231_03114

EOBD variantsThe description and explanation of EOBD is more detailed than the descriptions of individualcomponents or systems. The difficulties involved quickly become apparent when one considers thatEOBD is not an integrated vehicle system; many individual systems and components are continouslychecked for correct functioning. The various vehicle types, engines, engine control units, etc., also have tobe taken into account.To simplify matters, we will provide you with an overview of the various types of engine control unit andengine control units before explaining the test procedures.Basic types of engine control unitBasically, engine management systems are classified according to how operating states in the intakemanifold (air mass or intake manifold pressure) are determined. This classification is not referred tospecific engine control unit manufacturers, because they usually supply both types.The intake air quantity or intake manifold pressure are required to calculate- The ignition point- The injection quantity- And for EOBD monitoring of almost all components.Intake manifold pressure systemsIgnitionIntake manifold pressuresender G71InjectionIn these engine management systems, intake airquantity is determined with the aid of the intakemanifold pressure sender.These systems do not have an air-mass flowmeter.EOBD231_03415

EOBD variantsAir mass systemsAs the name suggests, the task of the air-massflow meter is to determine the intake air quantity.The intake manifold pressure sender is no longerrequired for this purpose.IgnitionAir-mass flow meterG70InjectionEOBD231_035Turbocharged engines have air-mass flow meters and intake manifold pressure sendersbecause the intake manifold pressure sender is also required to measure the charge pressure.Engine control units and air flow meteringThe various engine control units will now be assigned to the types of engine control unit (air flowmetering in intake manifold).Engine control unitsBosch Motronic ME 7.5.10Air flow meteringIntake manifold pressureBosch Motronic ME 7.1Air massBosch Motronic ME 7.5Air massBosch Motronic ME 5.9.2Air massMagneti Marelli 4LVIntake manifold pressureSiemens Simos 3Air mass16

Engine control units and diagnosticsIn the following table, the individual EOBD diagnostic routines are assigned to the engine control units.It can be seen that not all engine control units use the same diagnostic routines within the EOBD.Engine control unitsDiagnostic routinesSiemensSimos 3MagnetiMarelli 4LVBoschMotronicM 5.9.2Comprehensive Components MonitoringVoltage curve shift and adaption of probe beforecatalystLamdba probe heater diagnosisReaction time diagnosis ofprobe before catalystControl limit diagnosis ofprobe after catalystMotion diagnosis ofprobe after catalystCatalytic conversion diagnosisFuel tank purging systemFlow rate diagnosisFuel tank purging systemModulation diagnosisMisfiringIrregular running methodMisfiringMoment analysis methodExhaust gas recirculationPressure diagnosisElectric throttle driveCAN databusData diagnosisSecondary airFlow rate diagnosisCharge pressure limit diagnosis17

EOBD variantsEngine control unitsDiagnostic routinesBoschMotronicME 7.1BoschMotronicME 7.5BoschMotronicME 7.5.10Comprehensive Components MonitoringVoltage curve shift and adaption ofprobe before catalystLamdba probe heater diagnosisReaction time diagnosis ofprobe before catalystControl limit diagnosis ofprobe after catalystMotion diagnosis ofprobe after catalystCatalytic conversion diagnosisFuel tank purging systemFlow rate diagnosisFuel tank purging systemModulation diagnosisMisfiringIrregular running methodMisfiringMoment analysis methodExhaust gas recirculationPressure diagnosisElectric throttle driveCAN databusData diagnosisSecondary airFlow rate diagnosisCharge pressure limit diagnosis18

Diagnostic routinesMany of the diagnostic routines were previously explained and described inSelf-Study Programme 175. To avoid repetition, new diagnostic routines will bedealt with in detail and known routines will be mentioned only. Known routinesare indicated by a red "icon" and the text "SSP 175".SSP 175Comprehensive Components Monitoring(Line-conducted faults)This diagnostic routine monitors the functioning of all sensors, actuators andoutput stages that are relevant to exhaust emissions within the frameworkof the EOBD.For details of the individual components, refer to the function diagrams.SSP 175Components are tested according to the following criteria:- Check of input and output signals (plausibility)- Short circuit to earth- Short circuit to positive- Open circuitLambda probeVoltage curve shift diagnosis and adaption of the probe before the catalystAgeing or poisoning can cause a shift in the voltage curve of the probe before thecatalyst. This shift is detected by the engine control unit and can be compensated(adapted) within defined bounds.The diagnosis sequence is basically the samedespite the new broadband lambda probe.SSP 175Lamdba probe heater diagnosisBy measuring the probe heating resistance, the engine control unit checks theheat output of the lamdba probe heater for correctness.SSP 17519

Diagnostic routineReaction time diagnosis of probe before catalystThe reaction time of the probe before the catalyst can also deteriorate due to ageing or poisoning.The procedure for diagnosis of these faults was previously explained in Self-Study Programme 175.However, the signals from the probe before the catalyst have changed due to the use of broadbandlambda probes. Hence, the description of this diagnosis routine with the current signals from probebefore the catalyst.Modulation of the fuel/air mixture by the enginecontrol unit is prerequisite for reaction timediagnosis. This modulation takes the form ofslight fluctuation between lean and rich mixture.It is induced artificially by the engine control unit,because the lambda value can be controlled byusing the broadband lambda probe to such ashigh degree of accuracy that it is possible tomaintain a constant value of λ=1. For optimaloperation, however, the catalyst requires themixture composition to fluctuate slightly.Therefore, the engine control unit modulates thismixture when a broadband lambda probe isbeing used.Mixture modulation of the engine control unitUrich mixtureλ=1lean mixturetU = voltage, t = time 231_048The signal from the broadband lambda probe is specified here as voltage U, because theVehicle Diagnostic, Testing and Information System VAS 5051 converts the actual output signal(current intensity Ι) into a voltage and displays this value.20

● The signal from the probe before the catalystfollows modulation of the fuel/air mixture bythe engine control unit.● The signal from the probe before the catalystcan no longer follow modulation of thefuel/air mixture.Probe beforecatalyst OKProbe beforecatalyst not OK1231_044 231_045UUUUtttt23U = voltage, t = time1 Engine control unit2 Probe before catalyst3 Probe after catalyst21

Diagnostic routinesControl limit diagnosis of probe after catalystWhen the fuel/air mixture is of optimal composition, the voltage of the probe after the catalyst will be inthe region of λ=1. If the probe after the catalyst produces a higher or lower average voltage, thisindicates that the fuel/air mixture is too rich or too lean. The engine control unit therefore changes itslambda control value (this affects the fuel/air-mixture composition) until the probe after the catalystagain signals λ=1. This lambda control value has defined control limits. If these control limits areexceeded, EOBD assumes that there is a fault in the probe after the catalyst or in the exhaust system(secondary air).● Lean fuel/air mixture and correct controlThe probe after the catalyst signals a rise in oxygenconcentration in the exhaust gas to the enginecontrol unit through a voltage reduction. The enginecontrol unit then increases the lambda control value,and the fuel/air mixture is enriched. The voltage ofthe probe after the catalyst rises and the enginecontrol unit is again able to reduce the lambdacontrol value. This control loop extends over alengthy vehicle operating period.m1tControl loop aftercatalyst OK231_015Uλ=1t2m = lambda control value, U = voltage, t = time● Lean fuel/air mixture and reaching of control limitvalueControl loop aftercatalyst not OKIn this case, too, the probe after the catalyst signalsa rise in oxygen concentration in the exhaust gas tothe engine control unit through a voltage reduction.The engine control unit then increases the lambdacontrol value, and the fuel/air mixture is enriched.Despite this enrichment of the fuel/air mixture, theprobe voltage remains low (due to the fault) and theengine control unit continues to increase the lambdacontrol value until the control limit is reached andthe fault is detected.mt231_014Uλ=1t1 Engine control unit2 Probe after catalyst22

Motion diagnosis of probe after catalystThe operating performance of the probe after the catalyst is monitored also. To this end, the enginecontrol unit checks the signals from the probe in acceleration and overrun modes.When the vehicle is accelerating, the fuel/air mixture is rich, the oxygen concentration in the exhaust gasdecreases and the probe voltage must rise. In overrun mode, the exact opposite applies: fuel feed is off,the oxygen concentration in the exhaust gas increases and the probe voltage must drop. If the probeafter the catalyst does not react as expected, the engine control unit assumes that the probe after thecatalyst is defective.● Example: vehicle accelerationProbe after catalystOKProbe after catalystnot OK1231_016 231_017vUvUtttt2v = vehicle road speed, U = voltage,t = time1 Engine control unit2 Probe after catalystCatalystCatalytic conversion diagnosisThe engine control unit compares the voltages of the probes before and after thecatalyst. In this way, the degree of efficiency - and hence the performance - of thecatalyst can be determined.SSP 17523

Diagnostic routinesFuel tank purging systemFlow rate diagnosisWhen the fuel tank purging system is activated, the fuel/air mixture changes.If the activated charcoal canister is full, the mixture will be rich. If the activatedcharcoal canister is empty, the mixture will be lean. This change of mixturecomposition is registered by the probe before the catalyst and serves asconfirmation that the fuel tank purging system is functioning properly.SSP 175Modulation diagnosisThis diagnosis routine carries out checks cyclically. The engine control unit opens and closes activatedcharcoal filter system solenoid valve 1 slightly at defined intervals. The intake manifold pressure senderrecords the intake manifold pressure "modulated" in this way and sends this pressure value to the enginecontrol unit where it is correlated and evaluated.Fuel tank purgingsystem OKFuel tank purgingsystem not OK1231_009 231_010aPaPtttt3452a = opening stroke of solenoid valvet = time, P = pressure1 Engine control unit2 Tank3 Activated charcoal canister4 Activated charcoal filter system solenoidvalve N805 Intake manifold pressure sender G7124

Cylinder-selective misfiring detection systemIrregular running methodThe engine speed sender can recognise irregularities in engine speed caused bymisfiring with the aid of the crank disk.In combination with the signal from the Hall sender (camshaft position), theengine control unit can locate the cylinder in question, save the fault to faultmemory and activate self diagnosis fault warning lamp K83.SSP 175Moment analysis methodAs with the irregular running method, the moment analysis method recognises cylinder-selective misfiringfrom the signal supplied by the engine speed sender and the Hall sender. The difference between thesetwo methods lies in the way the engine speed signal is evaluated. The moment analysis methodcorrelates the irregular engine speed caused by ignition and compression with fixed calculations in theengine control unit. The basis for these calculations is the engine load and engine speed dependenttorque, the centrifugal mass and the resulting engine speed characteristic.The fluctuation in engine moment calculated in this way is equally as conclusive as the results of theirregular running method, but the engine speed characteristic is required to be analysed for each engineand stored in the engine control unit.● Irregular engine speedCompression ratio in cylinder 1nFor the sake of simplicity, only the 1st cylinderwill be examined in this example.During the compression cycle, the kineticenergy of the engine is used to compress thefuel/air mixture. Engine speed decreases.tn = engine speed, t = time231_01825

Diagnostic routineThe compression cycle is followed by the ignitioncycle, and engine speed is increased. In this way,engine speed is made to fluctuate bycompression and ignition during eachcombustion cycle.Ignition in 1st cylindernWhen all four cylinders are examined, theindividual engine speed fluctuations aresuperposed to produce a resulting curve.This curve is measured by the engine speedsender and checked by the engine control unitagainst a calculation made with characteristicengine data.t231_019● Misfiring detection using the engine speed signalnomisfiringmisfiring1nntt2231_020 231_021n = engine speed, t = time1 Engine control unit2 Engine speed sender G28If the EOBD exhaust emission limits are exceeded due to misfiring, then the self diagnosis faultwarning lamp will be lit continuously.If, however, there is a risk of misfiring causing damage to the catalyst and the engine is runningwithin the critical load RPM range, the self diagnosis fault warning lamp initially flashes and ashort time later the fuel feed to the corresponding cylinders is shut off.26

Electrical exhaust gas recirculationPressure diagnosisWhile exhaust gas is admitted into the intake manifold, the intake manifold pressure sender must registera rise in pressure (less partial pressure). The engine control unit compares the pressure rise in the intakemanifold with the supplied exhaust gas quantity and can thus determine whether the exhaust gasrecirculation (EGR) system is functioning properly. This diagnosis is only carried out in overrun mode,because injection is deactivated as a disturbing influence for measurement and the intake capacity ofthe engine is very high.1P+EGROKP+EGRnot OK1 Engine control unit2 EGR valve N183 Intake manifoldpressure sender G71ttP-P-23231_022 231_023P+ = excess pressure, P- = vacuum, t = timeElectric throttle driveThe EOBD uses the electrical throttle control diagnosticfunctions which indicate a fault via the electric throttle controlfault lamp.If these faults still exist during the next one or two drivingcycles, the EOBD also activates the exhaust gaswarning lamp.For more detailed informationrelating to the diagnosticfunctions of the electricalthrottle control, please refer toSelf-Study Programme 210.The electric throttle drive checks:- the function processor in the engine control unit- the accelerator position sender- the angle senders for throttle valve drive- the brake light switch- the brake and clutch pedal switch- the vehicle road speed signal27

Diagnostic routinesCAN databusData diagnosisEach engine control unit knows the electroniccomponents which exchange information via theCAN databus in the vehicle. If the minimumnumber of messages is not received from acomponent, a fault is detected and saved.Further components which the CAN databususes include:- Control unit with display unit in thedash panel insert- ABS control unit/ESP- Automatic gearbox control unit● CAN databus in proper service conditionAll connected components(in this case: control units) regularly transmitmessages to the engine control unit.The engine control unit recognises that nomessages are missing and data is beingexchanged properly.● CAN databus interruptedA component cannot transmit information tothe engine control unit. The engine controlunit notices the missing information, identifiesthe component affected and saves acorresponding fault message to fault memory.CAN databusOKCAN databusnot OK1231_024 231_0252ABCA B C1 Engine control unit2 CAN databusA-CVarious control units on board the vehicle28

Secondary air systemThe performance of the secondary air system was previously tested via the lambda control value.This means that the voltage present at the probe before the catalyst must indicate a lean mixture duringsecondary air discharge (λ>1) although the engine control unit is running the engine on a rich mixture.Flow rate diagnosisSince the introduction of the broadband lambda probe, the signal from the probe before the catalyst isused for diagnosis purposes, because the broadband lambda probe supplies more detailedmeasurement results than the step type lambda probe for example. The actual air mass flow is calculatedand checked on the basis of the lambda differential (lambda value before and during secondaryair discharge).Secondary airsystem OKSecondary airsystem not OK1231_026 231_0272λλ435tt6λ = lambda, t = time1 Engine control unit2 Secondary air pump relay J2993 Secondary air inlet valve N1124 Secondary air pump V1015 Combi valve6 Probe before catalyst29

Diagnostic routineCharge pressure controlCharge pressure limits diagnosisIn turbocharged engines, charge pressure is checked for exceeding the maximum permissible valuewithin the framework of the EOBD. The check also serves to protect the engine, which must not beoverloaded by excessively high charge pressure.● The charge pressure limit is exceededThe maximum permissible charge pressure isexceeded due to a fault in the chargepressure control. The intake manifold pressuresender signals the presence of chargepressure to the engine control unit, and theengine control unit detects the fault.● The protective function is initiatedIn this case, it is not enough to indicate andsave the fault. The exhaust gas turbochargerhas to be deactivated in order to avoiddamaging the engine. For this purpose, the"waste gate" of the turbocharger is openedand the driving exhaust gases are divertedthrough it.Charge pressurecontrol not OKCharge pressurecontrol not OK1231_028 231_029PP2tt53Exhaust gas4P = pressuret = time1 Engine control unit2 Solenoid valve for charge pressure control N753 Exhaust gas turbocharger with charge pressurecontrol valve4 Waste gate5 Intake manifold pressure sender G7130

Notes31

Self diagnosisReadiness codeAll electrical components are continuouslychecked for proper functioning within theframework of the EOBD. In addition, integratedsystems (e.g. exhaust gas recirculation system)are checked by non-continuous diagnosticroutines.The readiness code is set to checkwhether these diagnoses were performed or not.The readiness code consists of an 8-characternumber code; a 0 (diagnosis performed) or a 1(diagnosis not performed) can be assigned toeach digit position.The readiness code does not check for faultsoccurred; it indicates only whether diagnoseswere performed.If the diagnoses produce no erroneous entries,the systems are in proper service condition.The engine control unit sets the readiness codewhen:- the readiness code is cancelled- the engine control unit is put into operationfor the first time.Vehicle self diagnosisSelect diagnosticfunction02 - Interrogate fault memory03 - Actuator diagnosis04- Basic setting05 - Clear fault memory06- End of output07 - Code control unit08- Read data block09- Read individual measured value10 - Adaptation11 - Login procedure15 - Readiness code01 - Engine electronics036906034BBMarelli 4LV 3253Code 31Dealership number 5Vehicle self diagnosis15 - Readiness code10100001 Test not completeCare should be taken to ensure that thefault memory is not erasedunnecessarily, because this also causesthe readiness code to be reset orerased.01 - Engine electronics036906034BBMarelli 4LV 3253Code 31Dealership number 5TestInstrumentsGo toPrint231_058TestInstrumentsGo to Print HelpThe readiness code marked above represents theperformance status of the following systems in thegiven order:1. Catalyst2. Catalyst heating3. Fuel tank purging system4. Secondary air system5. Air conditioning system6. Lambda probe7. Lamdba probe heater8. Exhaust gas recirculation32

Unused digit positions of the readiness code are generally set to "0", because not all diagnosesare available in all vehicles.Read out readiness codeThere are two possible ways to read out the readiness code.- Using any Generic Scan Tool (OBD visual display unit) or- Using the Vehicle Diagnostic, Testing and Information System VAS 5051.The procedures are explained on the following pages.Generate readiness codeThe readiness code can only be generated by running the diagnoses.There are three possible ways to do this:- Perform an NEFZ ("Neuer Europäischer Fahrzyklus" = new European driving cycle).However, the standard workshop will be unable to perform the NEFZ on a roller dynamometer uponcompletion of repair work.- Run the vehicle in average operating mode for long enough(this may necessitate several trips).- Using the VAS 5051 diagnostic system, perform a defined test routine (short trip) for each relevantvehicle system.The procedure is also explained in "Vehicle Diagnostic, Testing and Information SystemVAS 5051".Generic Scan Tool (OBD visual display unit)It must be possible to read out emission-related faults and data acquired by the engine control unitwithin the framework of the EOBD using any OBD visual display unit. Therefore, the detected faults aresaved using an SAE code. This SAE code is used by all OBD systems.SAE code:- P0xxx: Codes with set fault texts defined by the SAE (Society of Automotive Engineers)(same for all automobile manufacturers)- P1xxx: Codes defined by automobile manufacturers which are required to be reported to thegovernment (these codes are defined differently for different automobile manufacturers)33

Self diagnosisAn OBD visual display unit can be put intooperation simply by connecting it to thediagnosis interface in the passenger cabin.Communications between the engine control unitand OBD visual display unit will be establishedautomatically.For fault tables for the SAE codes, referto the Workshop Manual of the relevantengine control unit.re. Mode 3 and 7:For fault acknowledgement, severaldiagnosis routines require one or moretrips until the self diagnosis faultwarning lamp is activated.An OBD visual display unit facilitates thefollowing functions:- Mode 1:Read out current engine operating data(actual data, readiness code).- Mode 2:Read out operating conditions which existedwhile saving a fault(only used if a fault has occurred).- Mode 3:Read out emission-related faults which havecaused the self diagnosis fault warning lampto be activated.- Mode 4:Erase fault code, readiness code andoperating conditions (Mode 2).- Mode 5:Display lambda probe signals.- Mode 6:Display measured values of non-permanentlymonitored systems (e.g. secondary air system,fuel tank purging system, exhaust gasrecirculation).- Mode 7:Read out faults which have still not activatedtheself diagnosis fault warning lamp.- Mode 8:This mode is not used in Europe.- Mode 9:Display vehicle information(e.g. ID No., engine code, engine control unittype, software identification, softwarechecksum).34

Vehicle Diagnostic, Testing and Information System VAS 5051Using VAS 5051, you can read out the readiness code and perform the individual short trips for thevehicle systems required to generate the readiness code.Over and above the functions of the OBD visual display unit, VAS 5051 provides additional adjustment,diagnosis and fault finding functions. The fault-finding procedure can be optimised by accessing all keyengine data.Read out readiness code1st possibility:- Turn on the ignition.- Activate "Vehicle self diagnosis" mode.- Select the engine control unit with addressword "01".- Select function "15 - Readiness code".2nd possibility (Generic Scan Tool-Mode)- Turn on the ignition.- Activate "Vehicle self diagnosis" mode .- Select Generic Scan Tool Mode with addressword "33".- Select Mode 1 "Read out actual engineoperating data".Perform short tripsUse function "04 – Initiate basic setting to invokethe individual short trips.Different procedures apply to the various enginecontrol unit variants.For details of the steps and preconditions forperforming the short trips of the variousindividual engine control unit variants, refer tothe relevant Workshop Manuals.231_04135

Function diagramExample 1: 1.4-ltr. 4V petrol engine 55 kW/Bosch Motronic ME 7.5.10J17+12V+12V+12V+12VSS S SSG61G188 G187 G186 J338N30N31N32N33+5VJ220+12VN152N80G39G130+12V231_053aComponentsG28 Engine speed senderG39 Lambda probe (before catalyst)G40 Hall senderG42 Intake air temperature senderG61 Knock sensor IG62 Coolant temperature senderG71 Intake manifold pressure senderG79 Accelerator position senderG130 Lambda probe after catalystG185 Accelerator pedal position sender -2-G186 Throttle valve driveG187 Throttle valve drive angle sender -1-G188 Throttle valve drive angle sender -2-G212 Exhaust gas recirculation potentiometerJ17 Fuel pump relayJ220 Motronic control unitJ338 Throttle valve control unit36

+12VSG79G185A B C+5V +5VJ220Input signalOutput signalPositiveEarthData line+5VG62 G28G40 N18 G212 G42 G71+12V231_053bN18 EGR valveN30 Injector, cylinder 1N31 Injector, cylinder 2N32 Injector, cylinder 3N33 Injector, cylinder 4N80 Activated charcoal filter system solenoid valve 1N152 Ignition transformerABCSignal to self diagnosis fault warning lamp K83(in models dating from 2000, this signal istransferred via the CAN bus)Road speed signal from control unitwith display unit in dash panel insert J285CAN busSFuse37

Function diagramExample 2: 1.4-ltr. 4V petrol engine 55 kW/Magneti Marelli 4LV+12VJ338G88 G69 V60N30 N31 N32 N33+12VJ17+12V+5VJ537N152+12VSN80G39G130+12V231_054aComponentsG28Engine speed senderG39Lambda probe (before catalyst)G40Hall senderG42Intake air temperature senderG61Knock sensor IG62Coolant temperature senderG69Throttle valve potentiometerG71Intake manifold pressure senderG79Accelerator position senderG88G130G212J17J537J338Throttle valve positioner potentiometerLambda probe after catalystExhaust gas recirculation potentiometerFuel pump relayControl unit for 4LVThrottle valve control unit38

G61G79A B C+5V +5V+5VJ537Input signalOutput signalPositiveEarthData lineG62 G40G28 G42 G71N18+12VG212231_054bN18 EGR valveN30 Injector, cylinder 1N31 Injector, cylinder 2N32 Injector, cylinder 3N33 Injector, cylinder 4N80 Activated charcoal filter system solenoid valve 1N152 Ignition transformerABCSignal to self diagnosis fault warning lamp K83(in models dating from 2000, this signal istransferred via the CAN bus)Road speed signal from control unitwith display unit in dash panel insert J285CAN busSFuseV60Throttle valve positioner39

Function diagramExample 3: 1.6-ltr. petrol engine 74 kW/Siemens Simos 3J17+12V+12VSS S SSG188 G187 G186J338N156N30N31N32N33+12V+5VJ361+12V+12VN152J299V101G61N80G39+12V231_055aComponentsG28 Engine speed senderG39 Lambda probe (before catalyst)G40 Hall senderG61 Knock sensor IG62 Coolant temperature senderG70 Air-mass flow meterG79 Accelerator position senderG130 Lambda probe after catalystG185 Accelerator pedal position sender -2-G186 Throttle valve driveG187 Throttle valve drive angle sender -1-G188 Throttle valve drive angle sender -2-G212 Exhaust gas recirculation potentiometerJ17 Fuel pump relayJ299 Secondary air pump relayJ361 Simos control unitJ338 Throttle valve control unit40

+12VN18G212G79G185A B CIn future, lambdaprobes by NTK will alsobe fitted in combinationwith Simos enginecontrol units.+5V +5V +5VJ361Input signalOutput signalPositiveEarthData line+5VN112G130G70G62G28G40+12V231_055bN18 EGR valveN30 Injector, cylinder 1N31 Injector, cylinder 2N32 Injector, cylinder 3N33 Injector, cylinder 4N80 Activated charcoal filter system solenoid valve 1N112 Secondary air inlet valveN152 Ignition transformerN156 Intake manifold change-over valveV101ABCSecondary air pumpSignal to self diagnosis fault warning lamp K83(in models dating from 2000, this signal istransferred via the CAN bus)Road speed signal from control unitwith display unit in dash panel insert J285CAN busSFuse41

GlossaryAdaptionAdapt to changed conditions.D2, D3, D4Exhaust emission standards of the FederalRepublic of Germany(refer to Self-Study Programme 230)NEFZ (Neuer Europäischer Fahrzyklus)New European driving cycle for determining theexhaust emissions of motor vehicles120kph600195 390 585 780 1180ElectrodeInterface between an electrical circuit and aliquid or gaseous environment(e.g. exhaust gas, ambient air)EOBDEuro On-Board DiagnosticsEU II, EU III, EU IVExhaust emission standard of the EuropeanUnion(refer to Self-Study Programme 230)sec.IWDS (Integrierter Wellendichtring-Sensor)Integrated shaft sealing ring sensorLambda(fuel-air ratio, λ)Factor which describes the air concentration inthe fuel/air mixture.λ1.0=lean mixtureλ=1.0=theoretical optimalmixing ratioTheoretically, λ is the air inflow rate to(theoretical) air demand ratio:Air inflow rate / air demand = lambda λLambda control valueThe engine control unit calculates the lambdacontrol value from the lambda probe signals andengine operating state (e.g. engine speed,engine load). Based on this value, the fuel/airmixture is altered until the optimum ratio for theoperating state is achieved.LSFLambda probe flat (step type lambda probe)LSHLambda probe heating (finger probe)LSULambda probe universal (broadband lambdaprobe)Generic Scan Tool(OBD visual display unit)It must be possible to read out all emissionrelatedfaults which the EOBD has detected viathe diagnosis interface with any OBD visualdisplay unit.The use of OBD visual display units for spotchecks is also planned.42

ModulationTo change or adapt the oscillation frequencyof a signal.Moment of forceThe moment of force (better known as"torque")is the product of an applied force and theassociated leverage.Moment of force = force x leverageForcePump cellThe pump cell comprises two electrodesseparated by a ceramic material permeable tooxygen. The oxygen ions O 2 (negativelycharged) are conducted through the ceramicfrom the negatively charged electrode (cathode)to the positively charged electrode (anode). Theresult is the so-called "pump effect".Readiness code8-character number code which indicateswhether the OBD diagnoses of the vehiclesystems were performed."0" - performed"1" - not performedSAE codeFault code defined by the Society of AutomotiveEngineers and binding for all OBD systems.LeverageExample with piston, connecting rod and crankshaftWaste gate(also known as "bypass")The waste gate passes excess exhaust gases bythe turbocharger drive. This allows theturbocharger to be deactivated or turbochargerpower output to be reduced.Nernst cell(part the of lambda probe)The Nernst cell measures the differentialbetween the oxygen concentrations in theambient air and the exhaust gases andgenerates a corresponding voltage U. TheNernst cell comprises two electrodes, one onthe ambient air side and and the other on theexhaust side.OBDOn-Board Diagnostics43

Test your knowledge1. Until when can buyers register new cars without EOBD if the new cars meet exhaust emissionstandard D3?a) 31.12.1999b) 01.01.2000c) 31.12.20002. When does self diagnosis fault warning lamp K83 begin to flash?3. What are the important points to note when replacing a broadband lambda probe (LSU)?a) The broadband lambda probe and the engine control unit are a system. Therefore, it is alsonecessary to replace the engine control unit.b) If the vehicle has two lambda probes, both probes must be replaced.c) The broadband lambda probe and the engine control unit are a system and must matchone another.d) The broadband lambda probe may only be replaced complete with cable and connectors.4. What is a Generic Scan Tool (OBD visual display unit) used for?a) The readiness code can be processed with it.b) Emission-related data, readiness codes, faults, fault conditions and vehicle data canbe read out with it. In addition, fault and readiness codes can be cancelled.c) Emission-related data, readiness codes, faults, fault conditions and vehicle data canbe read out with it. In addition, fault and readiness codes can be canceled and short tripscan be performed.44

Notes45

NotesSolutions:1. c2. If the catalyst can bedamaged due to misfiring.3. c, d4. b46

231For internal use only © VOLKSWAGEN AG, WolfsburgAll rights reserved. Technical specifications subject to change without notice.040.2810.50.20 Technical status: 05/00❀ This paper is produced fromnon-chlorine-bleached pulp.