Diagnostic Trouble Codes

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

After 3 consecutive drive cycles without a malfunction, ECM will turn off MIL, however DTC will be stored in ECM memory. If ECM does not detect that fault for 40 drive cycles, DTC will be cleared from ECM memory . ECM will clear a DTC for a misfire or fuel trim malfunction when fault is not detected for 80 drive cycles.

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, ECM will use a substitute value in its calculations to continue engine operation. See FAIL-SAFE MODE  under SELF-DIAGNOSTIC SYSTEM. In this condition, vehicle is functional, but driveability will be affected.