HARD FAILURES
Hard failures cause Malfunction Indicator Light (MIL) to illuminate and remain on until problem is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. See CODE CHARTS. If a sensor fails, PCME will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, the vehicle runs but driveability will not be optimum.
INTERMITTENT FAILURES
Intermittent failures may cause Malfunction Indicator Light (MIL) to flicker or illuminate and go out after the intermittent fault goes away. However, the corresponding trouble code will be retained in PCME memory. If related fault does not re-occur within a certain time frame, related trouble code will be erased from PCME memory. Intermittent failures may be caused by a sensor, connector or wiring related problems. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE section.
Memorized vs. Non-Memorized Codes
Some sensor or circuit failures are stored in PCME and are referred to as memorized codes. While other circuit failures, called non-memorized codes, are not stored. Non-memorized codes can be retrieved if ignition is not turned off before accessing codes.
Note. To access non-memorized trouble codes, DO NOT stop engine. Connect jumper wire across data link connector terminals TEN and GND. Observe MIL and note trouble codes.
Scheme 75
AFTER-REPAIR PROCEDURE
After indicated service or replacement is performed, clear codes. See CLEARING CODES. Recheck PCME memory. No codes should be present. If codes are present, see appropriate trouble code chart under CODE CHARTS to repair vehicle.
SUMMARY
If no hard fault codes (or only pass codes) are present, driveability symptoms exist or intermittent codes exist, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.