DIAGNOSTIC TROUBLE CODES (DTCs)

The Engine Control Module (PCM) monitors several different engine control circuits. If a malfunction occurs, PCM will record a Diagnostic Trouble Code (DTC). The next time engine is started and the same malfunction is detected PCM will turn on MIL, signaling a DTC is in PCM memory.

After 3 consecutive drive cycles without a malfunction, PCM will turn off MIL, however DTC will be stored in PCM memory. If PCM does not detect that fault for 40 drive cycles, DTC will be cleared from PCM memory. PCM will clear a DTC for a misfire or fuel trim malfunction when fault is not detected for 80 drive cycles with engine speed, coolant temperature, etc. similar to when malfunction first occurred.

Hard faults cause MIL to illuminate and remain on until the malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined. If a sensor fails, PCM will use a substitute value in its calculations to continue engine operation. See FAIL-SAFE MODE  under SELF-DIAGNOSTICS SYSTEM. In this condition, vehicle is functional, but driveability will be affected.