2002 MY OBD-II System Operation Summary - MotorCraftService.com

Catalyst Temperature ModelA catalyst temperature model is currently used for entry into the catalyst and oxygen sensor monitors. Thecatalyst temperature model uses various PCM parameters to infer exhaust/catalyst temperature. For the 1998MY, the catalyst temperature model has been enhanced and incorporated into the Type A misfire monitoringlogic. The model has been enhanced to include a misfire-induced exotherm prediction. This allows the model topredict catalyst temperature in the presence of misfire.The catalyst damage misfire logic (Type A) for MIL illumination has been modified to require that both the catalystdamage misfire rate and the catalyst damage temperature is being exceeded prior to MIL illumination. Thischange is intended to prevent the detection of unserviceable, unrepeatable, burst misfire during cold engine startupwhile ensuring that the MIL is properly illuminated for misfires that truly damage the catalyst.Serial Data Link MIL IlluminationThe instrument cluster on some vehicles uses the J1850 serial data link to receive and display various types ofinformation from the PCM. For example, the engine coolant temperature information displayed on the instrumentcluster comes from the same ECT sensor used by the PCM for all its internal calculations.These same vehicles use the J1850 serial data link to illuminate the MIL rather than a circuit, hard-wired to thePCM. The PCM periodically sends the instrument cluster a message that tells it to turn on the MIL, turn off theMIL or blink the MIL. If the instrument cluster fails to receive a message within a 5-second timeout period, theinstrument cluster itself illuminates the MIL. If communication is restored, the instrument cluster turns off the MILafter 5 seconds. Due to its limited capabilities, the instrument cluster does not generate or store DiagnosticTrouble Codes.FORD MOTOR COMPANY REVISION DATE: OCTOBER 02, 2001 PAGE 66 OF 66