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Home >> Acura >> 1999 >> 3.5RL >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1508: Idle Air Control (IAC) Valve Circuit

DTC P1508: Idle Air Control (IAC) Valve Circuit

  1. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine. If DTC P1508 resets, go to next step. If DTC P1508 does not reset, problem is intermittent. System is okay at this time. Check for poor connections or loose wires between IAC and PCM. Repair as necessary.
  2. Turn ignition off. Disconnect IAC valve 2-pin connector. Turn ignition on. Measure voltage between ground and IAC valve harness connector terminal No. 2 (Yellow/Black wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open in Yellow/Black wire between IAC valve and PGM-FI main relay.
  3. Turn ignition off. Reconnect IAC valve 2-pin connector. Disconnect 26-pin PCM connector. See Figure . Turn ignition on. Measure voltage between ground and PCM 26-pin connector terminal No. 5 (Black/Blue wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open or short in Black/Blue wire between IAC valve and PCM.
  4. Turn ignition on. Using a jumper wire, momentarily connect PCM 26-pin connector terminals No. 5 (Black/Blue wire) and No. 12 (Black wire). If IAC valve clicks, substitute a known-good PCM, then recheck. If symptom or indication goes away, replace original PCM. If IAC valve does not click, replace IAC valve.
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