Low Idle Speed
- Check Idle Air Control (IAC) valve circuit.
- Check A/C signal circuit.
- Check switch condition signal circuit. See CODE 51 in TESTS W/CODES - EXCEPT OBD-II article in the ENGINE PERFORMANCE section.
- Check Park/Neutral Position (PNP) switch circuit.
- Check fuel pump control circuit. See CODE 78 in TESTS W/CODES - EXCEPT OBD-II article in the ENGINE PERFORMANCE section.
- Check fuel injector circuit.
- Check Volume Airflow (VAF) sensor circuit. See CODE 31 in TESTS W/CODES - EXCEPT OBD-II article in the ENGINE PERFORMANCE section.
- Check ECM back-up power circuit (battery).