Introduction to On Board Diagnostics (II)

OBD II for L & MD VehiclesSTD ManualDiagnostic Test Modes (SAE J 11979):SAE 1979 defines the diagnostic test modes, and request and response messages necessaryto be supported by the vehicle manufacturers and test tools to meet EPA related OBD II requirements.These messages are for use by the service tool capable of performing rming OBD II diagnostics.Diagnostic test modes from mode $01 to Mode $08 are described in the standard. All test Modesexcept mode $ 08 are related to Request for Powertrain’s emission related diagnostic data or test resultsor Diagnostic trouble Codes. Test Mode $ 08 is Request for Control ol of On Board system instead of thedata. All these requests are made by the Scan Tool SAE J 1978.Mode $01 is request current powertrain diagnostic data which are:uAnalog inputs and outputsuDigital inputs and outputsuSystem status informationucalculated valuesMode $ 02 is request powertrain “Freeze Frame” data for the same items listed aboveMode $03 is request emission-relatedPowertrain Diagnostic Trouble Codes (DTCs(DTCs).Mode $04 is Clear/Reset emission related diagnostic information.Mode $05 is request Oxygen sensor monitoring test results.Mode $06 is request on-board monitoring test results for non-continuously monitored systems.Mode $07 is request on-board monitoring test results for continuously monitored systems.Mode $08 is request control of on-board system test, or component.For each test mode this standard specifies:uFunctional description of test mode.uRequest and response message formats.Examples of messages are included in the standard for explaining some complex test modes .The diagnostic message format, response time (100 ms) and various related data items are described indetail in the standard. PID $1D in table for Mode $01 is added as alternate locations for Oxygen Sensor.PID $1E in table for Mode $01 is added for Auxiliary input status. There are 14 figures showing 14 tables describingPIDs, , and messages for different Modes with their explanation including ing the method to determine if the data is valid.