DTC P1508: Idle Speed Control (ISC) Circuit
NOTE:
After each repair, clear DTCs. See CLEARING CODES/PCM RESET PROCEDURE
under SELF-DIAGNOSTIC SYSTEM. Turn ignition off and then on. Read DTCs to verify repair is complete. For DLC and PCM connector terminal identification, see CONNECTOR IDENTIFICATION
. For wiring diagrams, see WIRING DIAGRAMS
.
- Using scan tool, read DTCs. If DTC P1508 is present, turn ignition off. Ensure Idle Air Control (IAC) valve harness and connectors are not damaged and connections are okay. Repair as necessary. If harness and connectors are okay, go to next step.
- Disconnect IAC valve harness connector. Check continuity of wires between IAC valve harness connector and PCM harness connector as follows:
- Check Orange/Yellow wire between IAC valve connector terminal No. 1 and PCM Black connector terminal No. 3.
- Check Orange/Black wire between IAC valve connector terminal No. 2 and PCM Black connector terminal No. 16.
- Check Orange/Red wire between IAC valve connector terminal No. 3 and PCM Black connector terminal No. 28.
- Check Orange/Green wire between IAC valve connector terminal No. 4 and PCM Black connector terminal No. 29.
Repair wiring as necessary. If wiring is okay, go to next step.
- Check resistance between IAC valve terminals No. 1 and 2, and terminals No. 3 and 4. Resistance should be 40-60 ohms. If resistance is not as specified, replace IAC valve. If resistance is as specified, go to next step.
- Check for short circuit across evaporative control valve connector terminals. Repair wiring as necessary. If wiring is okay, clear DTCs. Turn ignition off and then on. Read DTCs. If DTC P1508 is not present, repair is complete. If DTC P1508 is present, replace PCM.