DTC P1508: Idle Air Control (IAC) Valve

Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DTCS . Start engine and warm to normal operating temperature. Allow engine to idle for at least 30 seconds. If DTC P1508 is indicated, go to next step. If DTC P1508 is not indicated, problem is intermittent, system is okay at this time. Check for poor connections or loose wires between Idle Air Control (IAC) valve connector and PCM connector. See the WIRING DIAGRAMS article.
Turn ignition off. Disconnect IAC valve 2-pin connector. Turn ignition on. Measure voltage between ground and IAC valve connector terminal No. 2 (Yellow/Black wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Yellow/Black wire between IAC valve connector and PGM-FI main relay. See the WIRING DIAGRAMS article.
Turn ignition off and reconnect IAC valve 2-pin connector. Disconnect PCM (32-pin) connector "A". See Figure . Turn ignition on. Measure voltage between ground and PCM connector terminal A12 (Black/Blue wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short in wire between IAC valve connector and PCM connector. See the WIRING DIAGRAMS article.
Using a fused jumper wire, momentarily connect PCM connector terminal A10 (Black wire) and terminal A12 (Black/Blue wire), several times. See Figure . If IAC valve does not click, replace IAC valve. If IAC valve clicks, substitute a known-good PCM and recheck. If symptom or indication goes away, replace original PCM.