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DTC P1508: Idle Air Control Valve

  1. Connect and operate scan tester, following manufacturer's instructions. Clear codes. Start engine. Retrieve codes. If DTC P1508 appears, go to next step. If DTC P1508 does not appear, problem is intermittent. Inspect for poor connections or loose wires associated with IAC and PCM, then repair as necessary.
  2. Turn ignition off. Unplug IAC valve connector. Turn ignition on. Measure voltage between ground and harness connector Yellow/Black wire. If battery voltage exists, go to next step. If battery voltage does not exist, repair open Yellow/Black wire between IAC valve and main relay.
  3. Turn ignition off. Reconnect wiring to IAC valve. Unplug PCM connector "A". See Figure . Turn ignition on. Test for battery voltage between ground and terminals No. 5 (Black/Blue wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short in Black/Blue wire between IAC valve and PCM.
    NOTE: When substituting a known-good PCM, immobilizer code must be rewritten using Honda PGM tester, or engine will not start.
  4. Turn ignition on. Using a jumper wire, momentarily connect terminals No. 5 (Black/Blue wire) and No. 12 (Black wire) at PCM harness connector "A". If IAC valve clicks, temporarily substitute known good PCM, then retest system. If IAC valve does not click, temporarily substitute known good IAC valve, then retest system.
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