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SURFACEVEHICLERECOMMENDEDPRACTICE

J1939-73

REV.MAR2004

Issued 1996-02

Revised 2004-03

SupersedingJ1939-731996-02

ApplicationLayer-Diagnostics

Foreword—TheJ1939seriesofSAERecommendedPracticeshasbeendevelopedbytheTruckandBusControlandCommunicationsNetworkSubcommitteeoftheTruckandBusElectricalandElectronicsCommittee.Theobjectivesofthesubcommitteearetodevelopinformationreports,recommendedpractices,andstandardsconcernedwiththerequirements,design,andusageofdeviceswhichtransmitelectronicsignalsandcontrolinformationamongvehiclecomponents.

TheseSAERecommendedPracticesareintendedasaguidetowardstandardpracticeandaresubjecttochangesoastokeeppacewithexperienceandtechnicaladvances.

TABLEOFCONTENTS

Foreword 1

Scope 4

References 4

ApplicablePublications 4

SAEPublications 4

CaliforniaAirResourcesBoard(CARB)Publication 4

Definitions 4

Active 4

Broadcast 5

Calibration 5

ContinuouslyMonitoredSystems 5

DiagnosticTroubleCode 5

FreezeFrame 5

Key 5

MalfunctionIndicatorLamp 5

MemoryAccess 5

Non-continuouslyMonitoredSystems 5

Object 5

Password 5

Pointer 5

Port 5

PreviouslyActive 5

Rationality 5

ReadinessCode 6

Seed 6

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Space 6

User_Level 6

Abbreviations 6

TechnicalRequirements 8

General 8

OverviewofDiagnosticRequirements 8

DiagnosticCapabilitiesEnvisioned 8

SuggestedDiagnosticSupport 8

EmissionRelatedComponents 8

Non-emissionRelatedComponents 9

GeneralConditionsforDiagnosticProcedures 9

Security 10

DiagnosticConnector 10

ParameterMonitoringRequirements 10

DiagnosticTroubleCodeDefinition 11

DiagnosticParameterGroupDefinitions 12

ActiveDiagnosticTroubleCodes(DM1) 14

MalfunctionIndicatorLamp 18

RedStopLamp 18

AmberWarningLamp 18

ProtectLamp 18

SuspectParameterNumber 18

FailureModeIdentifier 19

SPNConversionMethod 19

OccurrenceCount 21

PreviouslyActiveDiagnosticTroubleCodes(DM2) 21

DiagnosticDataClear/ResetofPreviouslyActiveDTCs(DM3) 22

FreezeFrameParameters(DM4) 23

FreezeFrameLength 24

FreezeFrameParameters 25

DiagnosticReadiness1(DM5) 25

ActiveTroubleCodes 25

PreviouslyActiveDiagnosticTroubleCodes 25

OBDCompliance 25

ContinuouslyMonitoredSystemsSupport/Status 26

Non-continuouslyMonitoredSystemsSupport 26

Non-continuouslyMonitoredSystemsStatus 27

ContinuouslyMonitoredSystemsTestResults(DM6) 28

CommandNon-continuouslyMonitoredTest(DM7) 29

TestIdentifier 30

TestResultsforNon-continuouslyMonitoredSystems(DM8) 30

TestType/ComponentIdentifier 31

TestValue 31

TestLimitMaximum 31

TestLimitMinimum 31

OxygenSensorTestResults(DM9) 32

Non-continuouslyMonitoredSystemsTestIdentifiersSupport(DM10) 32

TestIdentifiersSupported 32

DiagnosticDataClear/ResetforActiveDTCs(DM11) 33

Emissions-RelatedActiveDiagnosticTroubleCodes(DM12) 33

(R)5.7.13 StopStartBroadcast(DM13) 35

CurrentDataLink 40

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J1587 40

J1922 40

J1939Network#1,PrimaryVehicleNetwork 40

J1939Network#2 41

ISO9141 41

J1850 41

Other,ManufactureSpecifiedPort 41

J1939Network#3 42

HoldSignal 42

SuspendSignal 42

SuspendDuration 43

MemoryAccessRequest(DM14) 43

PointerType 44

PointerExtension 44

Pointer 45

Key/User_Level 46

Length/NumberRequested 48

Command 48

MemoryAccessResponse(DM15) 50

Status 51

EDCPExtension 52

ErrorIndicator/EDCParameter 53

Seed 58

Length/NumberAllowed 60

BinaryDataTransfer(DM16) 60

NumberofOccurrencesofRawBinaryData 60

RawBinaryData 61

BootLoadData(DM17) 62

BootLoadData 63

DataSecurity(DM18) 63

SecurityEntityType 63

SecurityEntityLength 64

DataSecurityParameter 64

CalibrationInformation(DM19) 65

CalibrationVerificationNumber 65

CalibrationIdentification 66

(R)5.7.20 MonitorPerformanceRatio(DM20) 68

IgnitionCycleCounter 69

OBDMonitoringConditionsEncountered 69

SPNofApplicableSystemMonitor 70

ApplicableSystemMonitorNumerator 70

ApplicableSystemMonitorDenominator 70

(R)5.7.21 DiagnosticReadiness2(DM21) 71

DistanceTravelledWhileMILisActivated 71

(R)AppendixA (R):FAILUREMODEIDENTIFIERCODES 72

AppendixB :AssumptionsUsedToDesignMemoryAccess 77

AppendixC :ApplicationRulesRegardingMemoryAccessPGNs 79

AppendixD :ApplicationRulesRegardingDataSecurityMessage(DM18) 88

AppendixE :MemoryAccessInformation 89

AppendixF :RestrictionsAssociatedwithproprietaryspns 99

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Scope

TheSAEJ1939seriesofrecommendedpracticesareintendedforlight-andheavy-dutyvehicleuseson-oroff-roadaswellasappropriatestationaryapplicationswhichusevehicle-derivedcomponents(e.g.generatorsets).Vehiclesofinterestinclude,butarenotlimitedto:on-andoff-highwaytrucksandtheirtrailers,constructionequipment,andagricultureequipmentandimplements.

Thepurposeofthesedocumentsistoprovideanopeninterconnectsystemforon-boardelectronicsystems.Itistheintentionofthesedocumentstoallowelectronicdevicestocommunicatewitheachotherbyprovidingastandardarchitecture.

J1939-73identifiesthediagnosticconnectortobeusedforthevehicleservicetoolinterfaceanddefinesmessagestoaccomplishdiagnosticservices.California-regulatedOBDIIrequirementsaresatisfiedwithasubsetofthespecifiedconnectorandthedefinedmessages.Diagnosticmessages(DMs)providetheutilityneededwhenthevehicleisbeingrepaired.Diagnosticmessagesarealsousedduringvehicleoperationbythenetworkedelectroniccontrolmodulestoallowthemtoreportdiagnosticinformationandself-compensateasappropriate,basedoninformationreceived.Diagnosticmessagesincludeservicessuchasperiodicallybroadcastingactivediagnostictroublecodes,identifyingoperatordiagnosticlampstatus,readingorclearingdiagnostictroublecodes,readingorwritingcontrolmodulememory,providingasecurityfunction,stopping/startingmessagebroadcasts,reportingdiagnosticreadiness,monitoringengineparametricdata,etc.

References

ApplicablePublications—GeneralinformationregardingthisseriesofrecommendedpracticesisfoundinSAEJ1939.ThelatestissueoftheSAEJ1939publicationsshallapply.

SAEPUBLICATIONS—AvailablefromSAE,400CommonwealthDrive,Warrendale,PA15096-0001.Unlessotherwisespecified,thelatestpublicationshallapply.

SAEJ1587—JointSAE/TMCElectronicDataInterchangeBetweenMicrocomputerSystemsinHeavy-DutyVehicleApplications

SAEJ1939—SerialControlandCommunicationsVehicleNetworkSAEJ1939-13—Off-BoardDiagnosticConnector

SAEJ1939-21—DataLinkLayer

SAEJ1939-71—VehicleApplicationLayerSAEJ1979—E/EDiagnosticTestModes

CALIFORNIAAIRRESOURCESBOARD(CARB)PUBLICATION—AvailablefromAirResourcesBoard,Haagen-SmitLaboratory,9528TelstarAvenue,ElMonte,CA91731-2990.Telephone(818)575-6800.

FINALREGULATIONORDER,Title13,CaliforniaCodeRegulations,Section1968.2,MalfunctionandDiagnosticSystemRequirementsfor2004andSubsequentModel-YearPassengerCars,Light-DutyTrucks,andMedium-DutyVehiclesandEngines(OBDII)

Definitions

Active—Thestateusedtoindicatethatafaultiscurrentlyoccurring.ActivedominatesPreviouslyActive.Afaultcannotbeboth“Active”and“PreviouslyActive”simultaneously.

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Broadcast—Messagesthataresentonaperiodicbasiswithouthavingtobesolicited.InsomecasesBroadcastsmaybenormallyoffandsolicitedtocomeonandthenstayonuntiltheyaresolicitedtoturnoff(seeDM13,sect.(R)5.7.13).

Calibration—Thesoftwareinstalledinacontrolmodule.Thisincludesexecutablecodeandcalibrationdata.

ContinuouslyMonitoredSystems—ContinuouslyMonitoredSystemsarethosewhicharemonitoredapproximatelytwotimespersecond.Notethatsomecontinuousmonitorsmayrequiremanyconditionstobetruebeforemonitoringcanbeperformed.

DiagnosticTroubleCode—A4-bytevaluethatidentifiesthekindoftrouble,theassociatedfailuremodeanditsoccurrencecount.

FreezeFrame—Asamplingofagroupofparametersbasedontheoccurrenceofadiagnostictroublecode.

Key—TheresultofasetofmathematicaloperationsperformeduponaSeedtoprovideadevicewithameansofauthenticatingaTool’srequest.

MalfunctionIndicatorLamp—TheMILisusedtoreporttroublecodesthatareemissionsrelated.TroublecodesthatarenotemissionsrelateddonotilluminatetheMIL.

MemoryAccess—Thisdefinesasetofmessages(DM14throughDM18)andoutlinestheoperationalproceduresforaTool(ordevice)wishingtoreadorwritethememory,orstoragespace,ofadevicewithorwithoutdatasecurity.

Non-continuouslyMonitoredSystems—Systemmonitorsthatrunonceatrip.Trip,inthiscontext,isasdefinedbyOBDII.Itshouldbenotedthattherewillbemonitorsthatwon’truneverytrip,i.e.cold-startaidmonitorsmayonlyrunwhentheambienttemperatureisbelow10°C(50°F).

Object—Someentitywithinamemoryand/oraSPACE.

Password—ThenumbersentwhenusingasimpleauthenticationtechniquewhereinboththedeviceandToolhaveapriorknowledgeofthespecificnumberandusuallyuseequalityastheverification.

Pointer—Atermusedtolabeladevicethatidentifiesthememorylocationwhichshouldbereadorwritten.Typesofpointersinclude:directmemoryaddressanddirectedspatialaddressing(SuspectParameterNumber(SPN)Space,OEMProprietarySpace,andReservedtobeassigned).

Port—Physicalconnectionpoint(s)fromacontrolmoduletoaspecificcommunicationslink(seeDM13).

PreviouslyActive—Thestateusedtoindicatethatafaulthasoccurredbutisnotpresentlyoccurring.Afaultcannotbeboth“Active”and“PreviouslyActive”simultaneously.

Rationality—Rationalityfaultdiagnosticforaninputcomponentmeansverificationoftheaccuracyoftheinputsignalwhileintherangeofwhatisphysicallypossible(seeAppendixA,regionbversusregionfandg)whencomparedtoallotheravailableinformation.ThisisatermthattheCaliforniaAirResourcesBoardhasdefinedintheirOBDIIrules.

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ReadinessCode—Thisisacodewhichissetoncealloftheemissions-relateddiagnosticshavebeenperformed.ThereadinesscodeshallbesetbeforethecompletionofthecoldportionoftheFederalTestProcedureforEmissionsCertification.Servicetoolscaninterrogateacontrollertodeterminethestateofthereadinesscode.Ifitisset,thenthecontrollerhashadtheopportunitytotestallemissions-relateddiagnostics(seeDM5,sect.5.7.5).

Forexample,onenginestartup,itislikelythatanin-rangetypeofdiagnosticontheintakemanifoldpressuremightrequireoperationatspeedandtorquepointsbeyondtheidlecondition.Therefore,ifthesystemhaditstroublecodeserasedandthentheenginewasrestarted,thereadinesscodewouldnotbesetuntiltheconditionforthein-rangeintakemanifoldpressuretestshadbeenexecuted.Itisalsoexpectedthatothertests,notjusttheintakemanifoldpressure,wouldneedtobeperformedbeforethereadinesscodecouldbeset.Thereadinesscodeshallgotothenotreadyconditioneachtimethevehicleispowereddown.

Seed—AnumbersentbyadevicetoaTooltoobtainauthenticationoftheTool’srighttoaccessthedevice.

Space—AmemoryregioncontainingacollectionofOBJECTS.

User_Level—AnumbersentbyaTooltoadevicealongwithaninitialrequesttoinformthedeviceofsomespecificlevelofaccessthattheToolwishestogain.

Abbreviations

CARB CaliforniaAirResourcesBoardCM SPNConversionMethod

CALID CalibrationIdentificationNumberCVN CalibrationVerificationNumber

DM1 DiagnosticMessage1,ActiveDiagnosticTroubleCodes

DM2 DiagnosticMessage2,PreviouslyActiveDiagnosticTroubleCodes

DM3 DiagnosticMessage3,DiagnosticDataClear/ResetforPreviouslyActiveDTCsDM4 DiagnosticMessage4,FreezeFrameParameters

DM5 DiagnosticMessage5,DiagnosticReadiness

DM6 DiagnosticMessage6,ContinuouslyMonitoredSystemsTestResultsDM7 DiagnosticMessage7,CommandNon-continuouslyMonitoredTest

DM8 DiagnosticMessage8,TestResultsforNon-continuouslyMonitoredSystemsDM9 DiagnosticMessage9,OxygenSensorTestResults

DM10 DiagnosticMessage10,Non-continuouslyMonitoredSystemsTestIdentifiersSupportDM11 DiagnosticMessage11,DiagnosticDataClear/ResetforActiveDTCs

DM12 DiagnosticMessage12,EmissionsRelatedActiveDTCs

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DM13

DiagnosticMessage13,StopStartBroadcast

DM14

DiagnosticMessage14,MemoryAccessRequest

DM15

DiagnosticMessage15,MemoryAccessResponse

DM16

DiagnosticMessage16,BinaryDataTransfer

DM17

DiagnosticMessage17,BootLoadData

DM18

DiagnosticMessage18,DataSecurity

DM19

DiagnosticMessage19,CalibrationInformation

DM20

DiagnosticMessage20,MonitorPerformanceRatio

DM21

DiagnosticMessage21,DistanceTravelledWhileMILisActivated

DTC

DiagnosticTroubleCode

EDC

ErrorDetectionand/orCorrection

EDCP

ErrorDetectionand/orCorrectionParameter

FMI

FailureModeIndicator

FTP

FederalTestProcedure

MA

MemoryAccess

MIL

MalfunctionIndicatorLamp

NA

Notapplicable

PG

ParameterGroup

PID

ParameterIdentifier(SAEJ1587orSAEJ1979)

OBDII

On-boardDiagnosticsII

OC

OccurrenceCount

SPN

SuspectParameterNumber

SeeSAEJ1939foranytermsandordefinitionsnotfoundinthisdocument.

SAE

TechnicalRequirements

General—ThediagnosticdefinitionsprovidedhereinareintendedtosatisfytheneedsofallpotentialusersoftheSAEJ1939network.ThesedefinitionsareintendedtobesuitableforapplicationsinanyoftheindustrygroupsdefinedwithinSAEJ1939.Abroadrangeofcapabilitiesareprovidedwithprovisionmadeforfuturegrowth.Additionalfeatures,ParameterGroupsandParameterdefinitionswillbedefinedovertime;itisanticipatedthatthisdocumentwillcontinuouslyevolveaslongastheSAEJ1939networkisanactiveRecommendedPractice.Suchgrowthwillbeimplementedinsuchawayastoensurebackwardcompatibilitywithearlierversions.Atthetimeofinitialpublication,manyofthesegrowthareasareidentifiedbutareyettobedefined.Suchidentificationisprovidedsothatthereaderwillbeawareofthoseadditionsthatarealreadyplannedforthedocument.

OverviewofDiagnosticRequirements—Thediagnosticrequirementsnecessarytoprovidethetypeofcapabilityourcustomers,ourindustry,andtheregulatorybodiesaredemandingisoutlinedinSection5.2.1.AdescriptionoftheminimumrequirementsneededtosatisfyregulatoryrequirementsiscontainedinSection

5.2.2.AdiscussionofthegeneraloperatingconditionsfordiagnosticproceduresisdefinedinSection5.2.3.

DIAGNOSTICCAPABILITIESENVISIONED—Thefollowingcapabilitieswillbedefinedinthisandfuturepublicationsofthisdocument:

Security—Defineasecurityschemetobeusedontheserialdatalinkthatallowstheindustrystandardservicetoolstobeabletoperformtasksthatarenecessaryduringserviceprocedures.Thiswillincludeaccessingdiagnosticinformation,accessingvehicleconfigurationinformationandrecalibratingcontrolmodules.

Connectors—DefinetheconnectortobeusedforconnectiontothevehicleSAEJ1939networkforservicetools.ThediagnosticconnectorisdefinedinSAEJ1939-13.

DiagnosticStatusMessageSupport—Provideasetofmessagesthatallowsthereadingoffaultinformation,clearingoffaultinformation,monitoringofvehicleparameters,accesstovehicleandcomponentconfiguration,andotherrelatedinformation.

DiagnosticTestSupport—ProvideacapabilitythatallowstheserviceTooltoputthevariouscontrollersintospecifictestmodesinordertodeterminepropersubsystemoperation.

SuggestedDiagnosticSupport

EmissionRelatedComponents—Asaminimumcapability,allcontrollersusingSAEJ1939thatimpactemissionsandmustcomplywithOBDIIorOBDshallsupportthefunctionsshowinthefollowingtable.

Table1:EmissionRelatedComponents

Row#

Function

PGN

Acronym

SPN#

Description

1

ReadDTCs

65236

DM1DM12

AllActiveDTCsEmissionsrelatedactiveDTCs

2

ClearDTCs

6523562228

DM11DM3

CleardiagnosticinformationforactiveDTCs

3

ReadFreezeFrameData

65229

DM4

Freezeframedefinition&support

4

Accessreal-timeinfo

SeeRows9-19

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Table1:EmissionRelatedComponents

Row#

Function

PGN

Acronym

SPN#

Description

5

Accesslasttriptestresults

65231

DM6

TestresultsforprematureDTCs

6

Accesssystemreadinesscode

65230

DM5

OBDcompliance,previouslyactive&activeDTCcount,monitorssupportedandtheirstatus.

Diagnosticreadiness.

7

ReportVIN

65260

VI

VehicleIdentification

8

ReportCVN

54016

DM19

Calibrationinformation

9

MonitorPerformanceRatio

49664

DM20

Indicateshowoftenmanufacturermonitorscomponentscomparedtototalnumberofopportunitiestomonitorcomponentperformance.

10

Temperature

65262

ET1

110

EngineCoolantTemperature

11

Speed

65265

CCVS

86

Wheel-basedVehicleSpeed

12

Pressure

65270

IC1

102

105

BoostPressure

IntakeManifoldTemperature

13

Positionsetting

61443

EEC2

91

92

AcceleratorPedalPositionPercentLoadatCurrentSpeed

14

Torque

61444

EEC1

513

190

ActualEnginePercentTorqueEngineSpeed

15

Angle

65159

IT6

1436

ActualIgnitionTiming

16

Group

60416

TP.CM.xx

2556

ConnectionManagement

17

Group

59392

ACKM

2541

AcknowledgementMessage

18

PGN

59904

RQST

2540

RequestPGN

19

Count

60160

TP.DT

2572

DataTransfer

Non-emissionRelatedComponents—Tobedeterminedinlaterrevisionsofthisdocument.

GENERALCONDITIONSFORDIAGNOSTICPROCEDURES—Theseguidelinesarenecessarytoensureproperoperationofboththetestequipmentandthevehicleduringdiagnosticprocedures.Testequipment,whenusingmessagesdefinedinthisdocument,shouldnotaffectnormaloperationofthevehicleexceptwhenthatistheexpresspurposeofthemessage.

Theoff-boardtestequipmentmayrequestdatawithoutknowledgeofwhichmoduleonthevehiclewillrespond.Theserequestsmayalsobedirectedtoaspecificdevice.Thepropermethodshouldbeusedinordertoreducenetworktraffic.Insomevehicles,multiplecontrollersmayrespondwiththeinformationrequested.Inaddition,asinglemodulemaysendmultipleresponsestoasinglerequest.Anytestdevicerequestinginformationmust,therefore,haveprovisionsforreceivingmultipleresponses.

Theon-boardsystemsshouldrespondtoarequestasdefinedinSAEJ1939-21.Withmultipleresponsespossiblefromasinglerequest,thisallowsasmuchtimeasisnecessaryforallmodulestoaccessthedatalinkandtransmittheirresponse(s).Ifthereisnoresponsewithinthistimeperiod(i.e.0.25seconds),theToolcaneitherassumenoresponsewillbereceived,orifaresponsehasalreadybeenreceived,thatnomoreresponseswillbereceived.

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AToolshouldalwayswaitforaresponsefromthepreviousrequest,or“noresponse”time-outbeforesendinganotherrequest.InnocaseshouldarequestbesentinlessthanthetimesspecifiedinSAEJ1939-21afterthepreviousrequest.

Destinationspecificrequestsrequirearesponse.Ifarequestforaparametergroupisnotsupportedbythemoduleandadestinationspecificrequestwasused,aNACKisrequired(seeSAEJ1939-21PGN59392).Iftherequestforaparametergroupwassenttoaglobaldestinationaddressanditisnotsupportedbyagivendevice,thenthatdevicemustnotNACKtherequest.

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Unlessotherwisespecified,parametervaluesshouldbeformattedinaccordancewiththeparameterrangesasdefinedbySAEJ1939-71section5.1.3.

Security—OneofthepurposesofthisRecommendedPracticeistoprovideastandardprotocol(asetofcapabilitiesordiagnosticservices)toallowuserstoaccessandmodifymemoryareasinsideacontrolleronthenetwork.ForthesetoolstobesupportedbythemanufacturersoftheECUsthatwillbedesignedtoconnecttotheJ1939network,sufficientprotectionagainst“unauthorized”modificationsmustbeincluded.Themessagesdescribedinsections5.7.14(DM14)though5.7.18(DM18)andtheirsubsectionsaretobeusedforthispurpose.

Thissecurityshallnotbeusedtolimitaccesstothecapabilitiesdefinedinsection5.7.1(DM1)throughsection

(R)5.7.13(DM13)andsection5.7.19(DM19),butisintendedtoallowmanufacturerstolimitthedatathatcanbeaccessedbytheuser.ThesecuritysystemsoutlinedhererepresentarecommendationforECUmanufacturersandprovideflexibilityforthemtotailorindividualsystemstotheirspecificsecurityneeds.Thevehiclemodulesaddressedarethosethatarecapableofhavingsolid-statememorycontentsalteredbyanexternalcommandsentthroughthisvehiclecommunicationlink.Impropermemorycontentalterationcouldpotentiallydamagetheelectronics,reducethevehicle’scompliancetolegislatedrequirements,orbreachthevehiclemanufacturer’ssecurityinterests.

Proper“Unlocking”ofthecontrollershallbeaprerequisitetoaccesscertaincriticalon-boardcontrollerfunctions.Accesstotheon-boardcontrollerwhileina“Locked”modeispermittedonlyasdeterminedbythecontroller’smanufacturer.Thismayrequirethattheuserobtainspecificcodesorpasswordsdirectlyfromthemanufacturer’srepresentativeandmayonlybepossiblewhenusingproduct-specificsoftware.Thispermitsthecontrollertoprotectitselffromunauthorizedintrusion.

Themessagesinsections5.7.14(DM14)though5.7.18(DM18)donotattempttodefinecapabilityasarequirementforanycontrollerortospecifywhatinformationshouldbesubjecttoanyspecificsecuritymeasures;thesedecisionsarelefttothecontrollermanufacturer.ImplementationofthesecuritysystemshallnotpreventbasicdiagnosticcommunicationsbetweenanexternalToolandtheon-boardcontroller.

AppendixC,AppendixDandAppendixEcontainadditionalinformationthatmayhelpimplementersunder-standtheintendeduseofthesesecurityprocessesforgainingaccesstocontrollermemoryandtheseveraldif-ferentmodesavailableforlimitingaccessareasofthatmemory.

DiagnosticConnector—ThediagnosticconnectorisdefinedinSAEJ1939-13.

ParameterMonitoringRequirements—TheparameterdefinitionsshallbethoseofthereferencedSAEJ1939ApplicationLayerdocument.AnyparameterthathasbeendefinedinanapplicationslayerdocumentandisincludedinaParameterGroup(PG)shallbeusedfordiagnostics.Therefore,ifaparameterhasalreadybeendefined,itwillnotberedefinedfordiagnosticpurposes.Insomecasesitwillbenecessarytoidentifyacloselyrelatedparameter,suchasthevalueoftheacceleratorpedalsensorreadingwhenthefailureoccurredratherthanthecurrentreadingoftheacceleratorpedalsensor.

SAE

DiagnosticTroubleCodeDefinition—ADiagnosticTroubleCode(DTC)ismadeupoffour(4)independentfields,asfollows:

a. SuspectParameterNumber

(SPN)

19

bits

b. FailureModeIdentifier

(FMI)

5

bits

c. OccurrenceCount

(OC)

7

bits

d. SPNConversionMethod

(CM)

1

bit

Theseindependentparametersarenotusedtogethertoformanumber.Theyaremerelyasetofinformationthathelpsinunderstandingthefailurethatisbeingreported.

AdiagnosticToolmayalsowanttousethecontrollersourceaddressandtheNametodeterminewhichcontrollerisreportingthediagnosticinformation.ThisinformationisnotneededtointerprettheSPNbutmaybebeneficialtohaveduringthediagnosticprocess.ReferenceSAEJ1939fortheSourceAddressandNamedefinitions.

Diagnostictroublecodesaretransmittedas4bytespertroublecode.Those4bytesareinterpretedasdefinedinsection5.7.1.InanefforttoprovidecontinuitybetweenthediagnosticsdefinedinSAEJ1587tothatofSAEJ1939-73,thefaultencodingformatremainsverysimilar.WhenpossibleSAEJ1587PIDnumbershavebeenmappedoneforoneasSPNs.

Examplesofdiagnostictroublecodes(seeTable2:):

EXAMPLE1—ThisisaSAEJ1587parameter.

SPN=91 SuspectparameterisacceleratorpedalpositionFMI=3 Failuremodeisidentifiedasvoltageabovenormal

OC=5 Occurrencecountindicatestroublehasoccurred5timesCM=02 (1bit)

EXAMPLE2—ThisisnotaparametercommunicatedasanSAEJ1587PID.Therefore,itisassignedanumberabove511.

SPN=656 Suspectparameterisengineinjectornumber6FMI=3 Failuremodeisidentifiedasvoltageabovenormal

OC=2 Occurrencecountindicatestroublehasoccurred2timesCM=02 (1bit)

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EXAMPLE3—DiagnosticTroubleCodeastransmittedindiagnosticmessages(e.g.DM1)Given:

Parameter“Pre-FilterOilPressure,”SuspectParameterNumber1208FailureModeIdentifierof3

OccurrenceCountof10

SPNConversion