SELF-DIAGNOSTICS
PCM constantly monitors all electrical circuits. If PCM detects circuit problems or sensors out of range, it will record a Diagnostic Trouble Code (DTC). If problem continues for a predetermined time, Malfunction Indicator Light (MIL) will glow.
If MIL is on all the time, DTC(s) are currently being detected. If MIL is off, but PCM had detected a circuit or sensor problem, DTC(s) will be stored in computer memory.
Stored DTCs may be retrieved from PCM memory. Depending on vehicle, several methods may be used. The most basic method (non-scan) uses a jumper wire to activate MIL, which will flash a series of codes.
Other methods include using a factory recommended Tech 1 scan tool, aftermarket scan tool or instrument panel mounted display (DeVille only).
Note. Faulty engine sensors and actuators may cause transaxle related DTCs or driveability problems. Engine faults and related DTCs must be diagnosed and repaired before transaxle codes are repaired. For additional information on diagnosing and repairing engine-related PCM trouble codes, see appropriate article in the ENGINE PERFORMANCE section.