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elec14 Six-Step Troubleshooting Plan.pdf

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ELEC14 SIX STEP TROUBLESHOOTING PLAN
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Body Electrical Diagnosis - Course L652 1 1. Introducethesix-steptroubleshootingprocess. 2. Explainwhatneedstobedonewhenverifyingaproblem. 3. Explainallthecomponentsofarelatedsymptomscheck. 4. Usingthecircuittracingtechnique,showhowtoanalyzethe symptomsanddefinetheproblemyouneedtodiagnose. 5. ShowhowtousetheEWDwhenisolatingaproblem. 6. Explainrepairtechniquesforwires,terminals,andconnectors. 7. PerformapracticecasestudyontheLexusBodyElectrical Simulatorusingthesix-stepapproach. Section 4 Six-Step Troubleshooting Plan Learning Objectives:Section 4 2 LEXUS Technical TrainingSix-Step Troubleshooting Plan Body Electrical Diagnosis - Course L652 3 Youhavenowcoveredallofthetools“usedwhendiagnosingelectrical problems: w Basicelectricalconcepts w UseoftheEWD w Tracingcurrentflowthroughasystemcircuitdiagram w UseoftheDVOM&jumperwires Nowit’stimetoputallofthesecomponentstogethertodiagnose electricalproblems. Itwouldbegreatifwecouldjustwalkuptoavehicleandinstinctively knowwhereanelectricalproblemwas,andwhatexactlyhadtobe donetorepairit.Thishappensoccasionallywhenfixingaproblemthat youhaveseenanumberoftimesonaparticularmodel.Your experiencefromrepeatedlyfixingthisproblemallowsyoutomakethe repairsquickly,withnowastedeffort. Butwhataboutproblemsthatyouseeononlyanoccasionalbasis, wherethereisnotrend“ofpastfailurestohelpyou?Todiagnosethese typesofproblems intheleastamountoftime ,youneedtomakeyour diagnosisfollowinga six-steptroubleshootingplan . InL623,theSix-StepTroubleshootingPlanwasintroduced.These stepsare: 1. Verifythecomplaint 2. Determinetherelatedsymptoms 3. Analyzethesymptoms 4. Isolatethetrouble 5. Correctthetrouble 6. Checkforproperoperation Byusingthistroubleshootingplan,youcanminimizetheamountoftime spentdiagnosingthecircuitbyperformingonlythechecksthatyou need tomake ,withanemphasisonchecksthatarethe easiesttomake . Quicklyfindingandfixinganelectricalproblemdoesn’tdependon luck,butonyour skills:applyingwhatyouknowaboutcircuits,using theEWD,anddevisingastrategytoisolatethelocationoftheproblem. Thesix-stepapproachisawaytoorganizeyourefforts,keepingyou on-trackwhileyouaretroubleshootingtheproblem. Introduction The Diagnostic Process Six-Step Troubleshooting PlanSection 4 4 LEXUS Technical Training Six-Step Troubleshooting PlanSix-Step Troubleshooting Plan Body Electrical Diagnosis - Course L652 5 Thisisthefirststepinanydiagnosticprocess.Whenyouarehandeda repairorderwithacustomer’scomplaintonit,therearethreethings thatyoumustdo: 1. Youmustbeableto identifytheproblemthecustomernoted 2. Youmust determineifitisaproblemornot 3. Ifthereisaproblem,determineifitis intermittentorcontinuous Theaveragecustomerisnotatechnicallyoriented“person.Whenthey describeaproblem,it’snotalwaysgoingtobeeasytounderstand them,especiallyifyouweren’tthepersonwhowroteitontheRO. Yourknowledgeabouthoweachsystemworksisveryimportantin recognizingwhatthecustomeristalkingabout.Ifyoudon’tknowhow asystemissupposedtooperatewhenit’sOK,you won’tknowwhenit isbroken.Becauseofthenumberofsystems/circuitsonthevehicleand theincreaseduseofECU-typecontrolsinthem,itisbecomingmore difficulttokeepupwiththedetailsonhowallthesystems,modelto model,operate. Thebestplacestolookforinformationonhowasystemshouldoperate arethe SystemOutline intheEWDandthe Owner’sManual . Verify the Complaint Step #1: Verify the Complaint Identify the ProblemSection 4 6 LEXUS Technical Training Sometimeswhatseemslikeaproblemtoacustomerisactuallya normalfunctionofthecircuit.Forexample,thecustomercomplaint couldbeaboutthepowerdoorlocks:Whenthekeyisintheignition, withthedooropen,thepowerdoorlockswon’tlock.“ Aconditionsuchasthisisnotaproblem,butanormalfunctionofthe PowerDoorLockECUanditskeyconfine“featurewhichisdesigned topreventthecustomerfromlockingtheirkeysinthecar.Forthe customer,informationabouttheoperationonalltheelectricalsystems onthevehiclecanbefoundinthe Owner’sManual .Foryou,detailed informationabouttheoperationofdifferentelectricalsystemscanbe foundinthe EWD,aswellasinthe RepairManualBodyElectrical section. Therearealsoinstanceswherethecustomerisnoticing acharacteristic ofthevehicle .Therearenofixes“forthesenon-problems.Thebest waytoidentifythistypeofconditionistocomparethecustomer’s vehicletoaknowngoodvehicle. Use the Owner’s Manual as a Reference Like the EWD system outline, the Owner’s Manual is a good resource for information on how different systems or circuits are supposed to operate. Does a Problem Exist?Six-Step Troubleshooting Plan Body Electrical Diagnosis - Course L652 7 Whenverifyingtheproblem,youmustalsodetermineiftheproblemis continuousor intermittent.Iftheproblemis continuous(ornotinter- mittent),itshouldbefairlyobviouswhenyouoperatethesuspectsystem. Intermittentproblems canbemoredifficulttofind.Iftheproblemis intermittent,you’llneedtoknowasmuchinformationaspossible(from theASMorcustomerdirectly)aboutthe conditions thatwerepresent whentheproblemoccurredforthecustomer. Forexample,electricalproblemscanbetriggeredbyambient temperature,vibrationsfromroadconditions,weather,orthetypeof driving(onlyonturns,hills,etc.)Howthecustomeractually operates thesystemcanalsobeafactor. Iftheconditionsarerepeatedandtheproblemdoesnot re-occur,makeathoroughvisualinspectionoftheharness,connectors, andterminals,withattentiontothe terminalspread .Simulatethe vibrationsthatarecausedduringdrivingbywiggling“harnessesand connectors.Keepinmindthatasyoumovetheharnessesordisconnect connectors,youmaycausetheproblemto temporarily fix“itself.While makingyourinspections,trytominimizethesechanges“tothecircuit, andkeeptrackofwhichharnessesorconnectorsyouhavedisconnected ormoved.Althoughitwillbedifficultinsomecases,besureto identify exactlywhatiscausingtheproblem ,and NEVER considerthe vehicle’sproblemsolvedifithappenstomagicallyfixitself“. Intermittent Problem Simulation Try to simulate the conditions under which the problem occurred. The ES 300 Repair Manual, has a Troubleshooting Section which was introduced to assist in diagnosing problems with ECU controlled systems. Intermittent or Continuous?Section 4 8 LEXUS Technical Training Ingeneral,youcannotmakeanaccuratediagnosisorrepairofa problemyoucannotduplicate.Ifthesituationwarrantsit, call TechnicalAssistance toseeiftherehavebeenanyotherreported casesoftheproblemorforadviceonhowtoproceedwiththevehicle. Nowthatyouhaveverifiedthat thereisaproblem ,youneedto examinetheproblemsymptomsmorethoroughly.Ther elated symptomscheck isbasicallyan operationalcheck ,soyouwon’t needanytoolsexceptfortheEWD.Themajorgoalofthischeckisto determine: 1. Howmuch ofthecircuitisaffected. 2. Findcluestothelocationoftheproblem byoperatingother circuitsrelatedorconnectedtotheproblemarea. Tosaydeterminetherelatedsymptoms“soundscomplex,butthisis oneofthemostimportantand timesaving stepsyoucanmakeinthe diagnosticprocess. Inthisstep,youneedtooperatetheproblemcircuitthoroughly,noting exactlywhatisandwhatisnotworking .Baseduponyour observations,makechecksto therelatedcircuits .Circuitsare related toanothercircuitbecauseofaparallelconnection: w Mostelectricalcircuitsconsistof twoormoreloads thatare connectedinparallel. w Entirelydifferentcircuitsare relatedtoanothercircuitbyaparallel connectionto commonpowersources(fuses)orground points. w Sharedsensororswitchfunctions inwhichasingleswitch operatesanumberofdifferentcircuits(suchastheLHfrontdoor courtesyswitchoperatingboththeinteriorlightingandkey warningbuzzercircuits). Step #2: Determine the Related Symptoms How a Circuit is “Related”Six-Step Troubleshooting Plan Body Electrical Diagnosis - Course L652 9 How Circuits are Related Circuits are related through shared fuse/power connections, and through splices on the +B or ground side of the component.Section 4 10 LEXUS Technical Training Inordertoknowwhatloadsorothercircuitsarerelated,you’llneedto lookintheEWD SystemCircuitDiagram .Thewiringdiagramwilltell youwhatloadsareconnectedinaparticularcircuit,andhowtheyare switched. SectionHPowerSource(CurrentFlowChart) ,aswellasthe powersourcesystemdiagram,willgiveyou+Bside“circuit information.Forgroundpointinformation,S ectionJ diagramsallof thesplicesonthegroundsideofthecircuits. Bycheckingtheoperationofrelatedcircuits,youwillbeeliminating partsofthecircuitorcomponentsasthepossibleproblemcauses.With feweritemsthatneedtobechecked,you’llspendlesstimeisolatingthe locationoftheproblem. Whileoperatingthecircuit,youneedtodetermineiftheproblem affectsallofthecircuitorjustpartofit.Baseduponhowthecircuit operates,youcanmakesomeassumptions: Iftheentirecircuitsystemisdead“,thisindicatesthat: w Thereisapossibleproblemwithapower(fuse)orgroundcircuit. w Theloadorcomponentisbad. Therearealargenumberofproblemsthatcouldcauseacomponent nottowork,fromanopenpowerwireorgroundwire,toasimplebad component.Becauseofthis,youneedaplacetostartyourinspection. Tobegin,theeasiestinspectiontomakewouldbeto checkthepower andgroundofthecomponent byoperatingrelatedcircuits.By usingtheEWD,makingaquickcheckofbothpowerandgroundis simple: w CheckingPower: Lookatthesystemcircuitdiagramand Section H,PowerSourceCurrentFlowChart todetermineothercircuits whichsharethefuseandchecktheiroperation.Evenifthefuseis notsharedbyanothercircuit,simplylocatingandinspectingthe fusecanbedonequickly. w CheckingGround: Operatingashared“circuitalsoprovidesa quickcheckofthegroundcircuit.Byusingthe SectionJ,Ground Pointinformation intheEWD,youcanfindoutifanothercircuit usesthesamegroundpoint.Ifacircuitwhichsharestheground worksOK,you’llknowthatthegroundpointisOK. Neitherofthesechecksisolatestheexactlocationofthecircuit problem.Buttheycanquicklypointtotheareasyouneedtocheckand saveyoufrommakingalotofunnecessaryinspections. How Much of the Circuit is Affected? If Entire Circuit is InoperativeSix-Step Troubleshooting Plan Body Electrical Diagnosis - Course L652 11 Check for Possible Fuse or Ground Problem If the whole circuit is inoperative, operate another circuit which uses the same fuse. Then operate another circuit that uses the same ground point.Section 4 12 LEXUS Technical Training Ifanypartofthecircuitstillworks: w Youknowthatthepowertothecircuitandthemaingroundpoint areprobablyOK. w Youneedtofindoutexactlywhichloadsareworkingandwhichare not.Thiswillletyoulookforcommonwiringorconnections betweenthebad“partsofthecircuit. Ifanypartoftheproblemcircuitworks,itisextremelyimportantto determineexactlywhichpartsareworkingandwhichparts arenot .Thisstepwillsaveyoufrommakingunnecessarychecksto partsofthecircuitthatareOK. Forexample,thecustomercomplaintisthatthestoplightsdonot work.Asyousteponthebrake,younoticethatthehighmountstop lightworks.Knowingthisverifiesthatalargeportionofthecircuitis OK.ByeliminatingpartsofthecircuitthatareOK,thenumberof placesyouneedtocheckisreduced.Thisiswhatcheckingtherelated symptomsisallabout. If Any Part of the Circuit WorksSix-Step Troubleshooting Plan Body Electrical Diagnosis - Course L652 13 Eliminate Parts of the Circuit If one or more of the stop lights work, you know that the fuse , the grounds, and part of the wiring are OK.Section 4 14 LEXUS Technical Training Whenworkingonasystemthathas self-diagnosticcapability ,the NewCarFeatures(NCF)bookandtheRepairManual(RM) are theonlyplacestofindinformationabouthowtoaccessthe Diagnostic TroubleCodes ,andwhateachindividualcodemeans.TheRMalso containsspecificdiagnosticproceduresforeachcircuit,includinga tabletodirectyouindiagnosingproblemsthatdonotsettroublecodes. Becausethemethodforaccessingthecodesvariesfromsystemto system,you’llneedtoturntothespecificRMsectionforeachofthese systems. Inthesecircuits,theEWDisbestused inconjunctionwith theRMand NCF.It’slocationtablesandcolorwiringdiagramsprovideagood supplementtotheRMinformation. Use the Repair Manual for Systems with Self-Diagnostics The RM is the first place to look when working with these systems. The EWD is helpful, especially with the color wiring diagrams, and location information. Circuits with Self-DiagnosticsSix-Step Troubleshooting Plan Body Electrical Diagnosis - Course L652 15 IfthecircuithasanECUwithself-diagnosticability,thegeneral diagnosticstrategyisto: 1. Alwayscheckfor DiagnosticTroubleCodes(DTC) first,and writethemdown.PointanyFreezeFramedataforreference. 2. Clearthecodememoryandoperatethesystem/vehicletoseeifthe problemisintermittentorcontinuous. 3. Ifthetroublecode(s)reappear,followthediagnostictablesinthe RM. 4. Iftherearenocodes,but thereisaproblempresent ,usethe ProblemSymptomsTableintherepairmanualtodirectyoutothe properinspections. 5. Whilediagnosingthecircuit, usetheEWDtohelpyoulocate thecomponents,pins,connectors,orsplices . Thereareothertechniquesthatyoucanusedependingonthesystem youarediagnosing.ThisadditionalinformationonECUsystem diagnosisiscoveredinL672. Diagnostic Trouble Codes (DTCs) DTCs are used in many body electrical systems including Cruise Control, Anti-lock Brakes, Airbag, and Engine Control Systems Diagnosing with DTCsSection 4 16 LEXUS Technical Training Inordertofixtheproblem,youneedtoknow exactlywhatproblem you’redealingwith.Whenverifyingtheproblem,youwereabletogeta betterunderstandingofthecustomer’scomplaint.Aftermakingthe relatedsymptomschecks,youmayhavefoundothercircuitsthatareor arenotaff
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