Component Description: Self-Diagnostics
The PCM/TCM constantly monitors all electrical circuits. If the PCM/TCM detects circuit problem(s) or out-of-range sensor(s), a trouble code(s) will be recorded in computer memory. If problem continues for a preset time, the TRANS or SERVICE ENGINE SOON light will glow.
If the TRANS or SERVICE ENGINE SOON light is always on, trouble code(s) is currently being detected. If the TRANS or SERVICE ENGINE SOON light is off, but PCM/TCM has detected a circuit or sensor problem, trouble code(s) will be stored in computer memory.
Stored trouble codes may be retrieved from PCM/TCM memory using "Scan" tool or TRANS or SERVICE ENGINE SOON light. See appropriate RETRIEVING CODES procedure under ELECTRONIC SELF-DIAGNOSTICS .
NOTE:
For complete PCM/TCM testing and diagnosis, see appropriate TESTS W/CODES article in the ENGINE PERFORMANCE section:
- For Diesel Vehicles, see TESTS W/CODES - DIESEL
- For Transmission Codes, see TESTS W/CODES - TRANSMISSION
- For V6 Equipped Vehicles, see TESTS W/CODES - V6
- For V8 Equipped Vehicles, see TESTS W/CODES - V8