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AT25 diagnostic procedures.pdf

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AT25 DIAGNOSTIC PROCEDURES
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Automatic Transmission Diagnosis - Course 273 1. Performallpreliminarycheckspriortotestdriving. 2. Relatetheimportancethatverifyingthecustomerconcernplays indiagnosis. 3. Explainthetypesoffluidcontaminants. 4. Explainholdingdevicediagnosisbasedonatimelagtest. 5. Performathoroughtestdrivefortransmissiondiagnosis. 6. PerformamanualshifttestofanECTtransmissionvehicle. 7. AccessdiagnosticcodesusingthediagnostictesterorflashingO/D OFFLightinearliermodels. 8. Checklinepressureatidleandstallspeed. 9. Monitorlinepressureduringautomaticandmanualupshift operation. 10. ExplainRepairManualfeatureswhichassistindiagnosis. Section 5 Diagnostic Procedures Lesson ObjectivesSection 5 TOYOTA Technical TrainingDiagnostic Procedures Automatic Transmission Diagnosis - Course 273 Diagnosisofanautomatictransmissionrequiresalogicalstepbystep procedurethatestablishesthecauseoftheproblem.Theprocedure musteliminateasmanycausesaspossiblebeforethetransmissionis removed.Toaccomplishthis,itisasimportanttodeterminewhatis working,asitistodeterminewhatisnotworking.Timespentin diagnosiswillhelpisolatetheproblemtooneofthefollowing: w enginedriveability w internalmechanicalorfrictiondiscfailure w hydrauliclogiccontrol w electronicsystemfailure Manydiagnosticcluesarenolongeravailableoncethetransmissionis removedandspreadoutonabench.Oncediagnosishasnarrowedthe cause,determinewhethertherepaircanbedonewiththetransmissionin thevehicleorifitneedstoberemoved.Additionally,willitbecosteffective torepairthetransmissionorreplaceitwithare-manufacturedunit? Diagnosisofautomatictransmissioncomplaintsshouldfollowa systematicsequenceofeventswhichresolvesthecustomer’sconcern. 1. VerifytheCustomerComplaint Isthereenoughinformation? 2. FluidChecks. Ensuretheproperlevelandconditionofthefluid. 3. TimeLagTest Verifyclutchengagementforfirstgearandreverse. 4. TestDrive Duplicatetheconditiontoexperiencethecustomer’sconcern. 5. RoadTest Thoroughevaluationofthetransmissionoperation. 6. DiagnosticTroubleCodes TheECMmonitorsthesensorsandsolenoidsandsetsatrouble codeinmemory. 7. PreliminaryChecksandAdjustments Verifiescommunicationbetweentheengineandtransmission. 8. ManualShiftTest Disconnectshiftsolenoidandverifytransmissionmanualoperation. 9. DiagnosticTesterUsage Analyzingthetestdriveresults. Diagnostic Procedures Diagnostic Sequence of EventsSection 5 TOYOTA Technical Training Verifyingthecustomercomplaintisthesinglemostimportantstepin diagnosis.Thetechnicianneedstoexperiencetheconditionandbeable toduplicateittoaccuratelydiagnoseit.Itisimpossibletorepaira complaintthatcannotbeverifiedorrepairaconditionthatisanormal characteristicofthevehicle’stransmission.Torepairaproblemfound duringdiagnosiswithoutensuringthatitfitsthecustomerconcern, runstheriskoffailingtomeetthecustomer’sexpectation. Communicationbetweenthecustomerandthetechnicianisessential toverifyingthecomplaint.Thetechnicianisfrequentlyisolatedfrom thecustomerandreceiveshisinformationthird-handfromtheService Writer.Tobridgethisgap,acustomerinterviewsheetisstrongly recommendedtoensurethetechnicianhasasmuchinformationas possibletobeginhisdiagnosticeffort.Themoredetailsthatare available,themorelikelytheconditioncanbefoundquickly.Asample CustomerInterviewSheetcanbefoundinAppendixE. Ifthecomplaintcannotbeverified,itmaybenecessaryto speakwiththecustomerandhavehim/heraccompanyyouon thetestdrivetoidentifytheirconcern. Thecustomerandvehicledataareforadministrativepurposesfor trackingthecustomerorvehicle.Additionally,it’simportantto determineifthepersonbringingthevehicleforserviceistheprimary operatorwhohasfirst-handknowledgeofthecomplaint. Askthecustomertoidentifythesymptom(s)bycheckingthe appropriateboxaswellasanysubsequentboxesthatclarifythe selection.Next,identifywhethertheconditionoccursconstantlyor intermittently. Threequestionsshouldbeansweredbeforeyoubeginyourdiagnostic proceduretoensureaproperrepairthefirsttime. 1. What isthespecificcomplaintor concern? Detailsofwhatthecustomersees,feels,andhearsasabnormal. 2. Underwhatconditionsdoesthecomplaintoccur? Coldorhotoperation,occursalways,intermittentlyorfirst engagementaftersittingovernight. 3. Whatisthevehicle’srecentservicehistory? Allservicebothmechanicalandbody/paint. Verify the Customer Complaint Customer Interview Sheet Customer and Vehicle Data Automatic Transmission DataDiagnostic Procedures Automatic Transmission Diagnosis - Course 273 Apreliminaryfluidcheckensuresthetransmissionhassufficientfluid andindicatestheconditionofthefluidpriortothetestdrive.Thereis noneedtotopoffthefluidunlessitisextremelylowandcouldcause furtherdamage.Donotattempttomakeanyadjustmentsorrepairs priortothetestdriveasthismaymaskthesymptoms.Besuretomake notesofyourfindingsontheROforfuturereference. Thefluidlevelshouldbeinspectedwhenthefluidhasbeenwarmedup tonormaloperatingtemperature,approximately158 5Fto176 5F.Asa ruleofthumb,ifthegraduatedendofthedipstickistoohottohold, thefluidishotenough.Properfluidlevelisinthehotrangebetween hotmaximumandhotminimum.Checkthefluidlevelyourselfand don’tassumethatsomeoneelsehasdoneitproperly. Thecoolrangefoundonthedipstickshouldbeusedasareferenceonly whenthetransmissioniscold,toensureadequatelubricationwhilethe fluidisbroughtuptotemperature.Thecorrectfluidlevelcanonlybe determinedwhenthefluidishot. Fluid Level Check The fluid is at the proper level if in the hot range between hot maximum and hot minimum. Properfluidlevelsensureproperoperationoftheholdingdevices,the torqueconverterandlubricationoftheautomatictransmission.Alow fluidlevelcausesdelayedengagementinbothdriveandreverseand slippingwhenupshifting.Slippingcausesoverheatingandrapidwear ofclutchesandbands.Additionally,fluidmaymigrateawayfromthe oilpickupunderheavydeceleration,resultinginalackofoilvolume requiredtodisengagethelockupconverterclutch. Preliminary Fluid Checks Fluid Level NOTESection 5 TOYOTA Technical Training Aerationoccurswhenfluidlevelistoolowortoohigh.Withlowfluid leveltheoilpumpdrawsair,causingittomixwiththefluid.Iffluid levelishigh,theplanetarygearsandotherrotatingcomponents agitatethefluid,aeratingitandcausingsimilarsymptoms. Theaeratedfluidcombinedwithoverheatingduetoslippage,causes thefluidtooxidizeandvarnishbuildsuponcomponents.Varnish interfereswithnormalvalve,clutchandaccumulatoroperation. Additionally,aeratedfluidwillriseinthecaseandleakfromthe breatherplugatthetopofthetransmissionhousingorthroughthe dipsticktube. Ifthelevelappearstobecorrect,checkforanairleakonthesuction sideofthepump.Checkthefilterinstallation,payingparticular attentiontothegasketorO-ring. Inadditiontothetransaxlefluidlevel,sometransaxlesrequirea separatecheckofthedifferentialfluidlevel.Thefluidisseparated fromthemainbodyofthetransaxlebyapairofsealsonthedrive pinion.Fluidlevelischeckedbyremovingthefillerplug.Fluidshould belevelwiththefillerplughole.Thischamberisdrainedandfilled separatelyfromthetransaxle.Althoughsometransaxlesareopento thedifferential,besuretocheckthedifferentialforproperlevelwhen refillingthetransaxle. Differential Fluid Level Check Some transaxles require a separate check of the differential fluid level. Differential Fluid LevelDiagnostic Procedures Automatic Transmission Diagnosis - Course 273 Twoindicatorsoffluidconditionhavebeencolorandsmell,butthese cannolongerberelieduponfordefinitivediagnosis.Sincetheremoval ofasbestosfromfrictionmaterialandtheaddedresincontent,the chemicalformulationsofnewfluidsandresinhavecontributedtothe smellandcolorchangesincurrentfluids.Adarkclearbrownordark clearredfluidcolordoesnotbyitselfindicateafailedunitevenifit smellsburned. Togetabetterindicationoffluidcondition,placeasampleofthefluid onawhitepapertowel. Analyzing Fluid Condition Place a sample of the fluid on a white paper towel for closer analysis of fluid condition. Ifanyoftheconditionslistedbelowarefoundinthefluidsample,the transmissionshouldberebuiltorreplacedwithare-manufacturedunit: w residueorflakyparticlesofmetalorfrictionmaterial. w heavilyvarnishedfluidwhichistackyandnolongerclear. w milkyappearingfluidcausedbyenginecoolantenteringthe transmission.Thecoolantmaycausethefrictionfacingtoloosen fromtheclutchplatesandtorqueconverterclutch Fluid ConditionSection 5 TOYOTA Technical Training Ifyou’rejustnotsureaboutthefluidconditionandresidueonthe dipstick,thetransmissionpancanberemovedafterthetestdriveto evaluatetheresiduecontent.Residuecanbeparticlesofsteel,bronze, plasticorfrictionmaterialreflectingdamagetobushings,thrust washers,clutchplatesorotherparts.Someresidueatthebottomofthe panisnotuncommon.Youwillfindtwoormoremagnetspositionedin thepantoattractmetalparticles,trappingthemfromsuspensionin thefluidandbeingtransportedthroughthetransmission.Theyare usuallycoveredwithsomemetalshavings. Remove Pan to Inspect Residue Residue can be particles of steel, bronze, plastic or friction material reflecting damage to bushings, thrust washers, clutch plates or other parts. Whenthefluidiscleanandresidueisminimal,chancesarethe problemwillnotberesolvedbyremovingthetransaxleand overhaulingitorreplacingitwithare-manufacturedunit.The problemislikelytobeoutsidethetransmission.Diagnostic Procedures Automatic Transmission Diagnosis - Course 273 Thetimelagtestisthemeasurementoftimefromthemovementofthe shiftleverfromneutraltodriveorreverse,untiltheengagementshock oftheholdingdevicesisfelt.Thisisusefultodeterminetheintegrityof thehydrauliclinepressure,the overdrivedirectclutch (C0), forward clutch(C1)andthe firstandreversebrake (B3).Lowlinepressureor wornclutchsealscancauseengagementshocktobedelayed. w Thetransmissionfluidshouldbeatnormaloperatingtemperature beforeconductingthetest. w Applytheparkingbrake w Starttheengineandcheckidlespeed w Usingastopwatch,makethreemeasurementsofthelagtimein driveandreverse. w Allowoneminutebetweenteststoallowfluidtoexhaustfromthe holdingdevices. w Usetheaveragetimetocompareagainstthespecifications Thechartbelowlistsseveraltransmissionsandtheholdingdevices appliedindrivefirstgear“andreverse.“Forexample,anA-540E’s properlagtimeis1.2secondsfromneutraltodriveand1.5seconds fromneutraltoreverse.Iftheaveragelagtimetodriveislongerthan 1.2seconds,oneormoreofthefollowingmaybeworn: forwardclutch (C1), No.2one-wayclutch (F2),or overdriveone-wayclutch (F0)and overdrivedirectclutch (C0).Lowlinepressuremaycauselate engagementinbothdriveandreverse. Time Lag Test Holding devices engaged in drive and reverse differ depending on the transmission application. Time Lag TestSection 5 TOYOTA Technical Training Thetestdriveisimportantfortworeasons.Itprovidesanopportunity toexperiencethetransmissionoperationalcharacteristicsfirsthand andultimatelyallowsfortheconfirmationofyourrepairs.Your primarypurposeshouldbetoduplicatethecustomersconcern. Iftheconcerncannotbeverifiedduringyourdiagnosis,moreinformation isneededandthereforeitisnecessarytospeakwiththecustomer. Itmaybenecessaryforthecustomertoaccompanyyouonthe testdrivetoidentifytheconcern. Theengineandtransmissionshouldbeatnormaloperating temperature.Whileinneutralpositionwiththeenginerunning,the vehicleshouldnotmoveeitherforwardorrearward.Ifthevehicledoes moveorcreep,notetheconditionandbesuretocheckthemanual linkageadjustment. Duringyourroadtest,operatethetransmissionthrougheachselector rangeaswellasforcedandmanualdownshifts.Checkforengineflare orclutchslipping,engagementquality,noiseandvibration.Noteyour findingsontheRepairOrder,oracopyoftheRoadTestProcedure Worksheetforeachgearposition. Fromastandstill,movethegearselectorintoD-range.Acceleratethe vehicleat1/4and1/2throttleopeningandnoteeachupshift.All upshiftsshouldoccurregardlessofthethrottleopening.However, upshiftswillvaryatdifferentthrottleopenings.Forexample,onalevel surfacetheupshiftfrom2ndto3rdwilloccuratahigherspeedathalf throttlethanatquarterthrottle. Whilein4thgear,moderatelyapplythethrottletotestthe4-3 downshift.Notetheresultandrepeatthelaststepatfullthrottle.At fullthrottle,dependingonvehiclespeed,thetransmissionmay downshifttothirdorsecondgear. Fromastandstill,movethegearselectorinto2-range.Acceleratethe vehicleat1/4and1/2throttleopening.Thetransmissionshouldshift from1stto2ndandholdin2ndgear.Thismanual2ndpositionshould provideenginebrakingondeceleration WiththegearselectorintheL-range,thetransmissionshouldnot upshiftto2ndandshouldhaveenginebrakingondeceleration. Test Drive Road Test D-Range 2-Range L-RangeDiagnostic Procedures Automatic Transmission Diagnosis - Course 273 Bringthevehicletoacompletestopandplacethegearselectorin R-range.Accelerateatpartthrottleandagainatfullthrottlefora shortdistancetochecktheoperation. Whentestdrivingavehicleunderheavyacceleration,particularlyin reverse,besuretoexerciseextremecaution.Beawareofvehicles, trafficandpedestriansinthearea. PresstheO/DOFFbuttononthegearselectorandcheckfora downshiftto3rdgear.At35mphorless,movethegearselectorfrom theDpositiontothe2positionandcheckforadownshiftto2ndgear. At25mphorless,movethegearselectorfromthe2positiontotheL positionandcheckforadownshifttofirstgear. On-boarddiagnostics(OBD)havebeenavailableonToyotaelectronic controltransmissionssincethemid-eighties.TheECMmonitorsinput andoutputcircuitsandcomparesthem
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