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DTC P1504: IAC Valve Circuit Malfunction: Testing

NOTE: Record freeze frame data. Check for service bulletins and on-line information.
  1. Using scan tool, clear DTC. Start engine. Warm engine to operating temperature. If DTC P1504 is present, go to next step. If DTC P1504 is not present, problem is intermittent. See TROUBLE SHOOTING - NO CODES article.
  2. Turn ignition off. Disconnect IAC valve connector. Check IAC valve connector terminals and IAC valve harness connector terminals. If problem is not present, go to next step. If any problem is present, repair as necessary. Go to step  12 .
  3. Measure resistance between IAC valve connector terminals. If resistance is 8.69-10.56 ohms, go to next step. If resistance is not 8.69-10.56 ohms, replace IAC valve. See WIRING DIAGRAMS article. Go to step  12 .
  4. Turn ignition on. Check voltage between IAC valve harness connector terminal No. 1 (Green/Yellow wire) and ground. If battery voltage is not present, problem is in power circuit. Go to next step. If battery voltage is present, problem is in control circuit. Go to step  8 .
  5. Turn ignition off. Disconnect PCM harness connector. PCM is mounted to passenger floor, behind glove box. Check PCM connector terminals and PCM harness connector terminals. If problem is not present, go to next step. If any problem is present, repair as necessary. Go to step  12 .
  6. Turn ignition off. Check for continuity between IAC harness connector terminal No. 1 (Green/Yellow wire) and ground. If continuity is not present, go to next step. If continuity is present, repair short to ground in wiring between IAC harness connector terminal No. 1 (Green/Yellow wire) and PCM harness connector terminal No. 54 (Gray/Blue wire). See Figure . See WIRING DIAGRAMS article. Go to step  12 .
  7. Turn ignition off. Disconnect PCM harness connector. Connect breakout box to PCM harness connector. Leave PCM disconnected. Check continuity between IAC harness connector terminal No. 1 and breakout box terminal No. 54. If continuity is present, go to step  12 . If continuity is not present, repair open in wiring between IAC harness connector terminal No. 1 (Green/Yellow wire) and PCM harness connector terminal No. 54 (Gray/Blue wire). Go to step  12 .
  8. Turn ignition off. Disconnect PCM connector. Check PCM and PCM harness connector terminals. If problem is not present, go to next step. If any problem is present, repair as necessary. Go to step  12 .
  9. Turn ignition on. Check voltage between IAC valve harness connector terminal No. 2 (Black/Yellow wire) and ground. If battery voltage is not present, go to next step. If battery voltage is present, repair short to power in wiring between IAC valve harness connector terminal No. 2 (Black/Yellow wire) and PCM harness connector terminal No. 83 (Gray/Blue wire). See Figure . Go to step  12 .
  10. Turn ignition off. Check continuity between IAC valve harness connector terminal No. 2 (Black/Yellow wire) and ground. See WIRING DIAGRAMS article. If continuity is not present, go to next step. If continuity is present, repair short to ground in wiring between IAC valve harness connector terminal No. 2 (Black/Yellow wire) and PCM harness connector terminal No. 83 (Gray/Blue wire). Go to step  12 .
  11. Disconnect PCM harness connector. Connect breakout box to PCM connector. Leave PCM disconnected. Check continuity between IAC harness connector terminal No. 2 (Black/Yellow wire) and breakout box terminal No. 83. If continuity is present, go to next step. If continuity is not present, repair open in wiring between IAC valve harness connector terminal No. 2 (Black/Yellow wire) and PCM harness connector terminal No. 83 (Gray/Blue wire). See Figure . Go to next step.
  12. Reconnect all components. Using scan tool, clear all DTCs. Start engine. Warm engine to operating temperature. Recheck DTCs. If same DTC is present, replace PCM and go to next step. If same DTC is not present, go to next step.
  13. Perform after repair procedure. See AFTER REPAIR PROCEDURE  . If DTC is not present, testing is complete. If any DTC is present, go to appropriate test for diagnosis and repair.
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