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DTC P0505: Idle Air Control Motor Circuits: Testing

  1. Turn ignition on. Using scan tool, read DTCs. If GLOBAL GOOD TRIP counter is displayed and displayed count is "0", go to next step. If GLOBAL GOOD TRIP counter is not displayed or displayed count is not "0", go to step  22.
  2. Start engine and allow it to idle. Disconnect IAC motor connector. Measure voltage between ground and terminal No. 1 (Gray/Red wire) at IAC motor harness connector. See Fig 1. If voltage changes to more than 5 volts at any time, go to next step. If voltage does not change to more than 5 volts at any time, go to step  19.
    Fig 1: Identifying Idle Air Control Motor Harness Connector Terminals
    G99C02260Courtesy of DAIMLERCHRYSLER CORPORATION
  3. With engine still idling, measure voltage between ground and terminal No. 2 (Yellow/Black wire) at IAC motor harness connector. If voltage changes to more than 5 volts at any time, go to next step. If voltage does not change to more than 5 volts at any time, go to step  16.
  4. With engine still idling, measure voltage between ground and terminal No. 3 (Brown/White wire) at IAC motor harness connector. If voltage changes to more than 5 volts at any time, go to next step. If voltage does not change to more than 5 volts at any time, go to step  13.
  5. With engine still idling, measure voltage between ground and terminal No. 4 (Violet/Black wire) at IAC motor harness connector. If voltage changes to more than 5 volts at any time, go to next step. If voltage does not change to more than 5 volts at any time, go to step  10.
  6. Turn ignition off. Ensure IAC motor is disconnected. Disconnect PCM connectors. PCM is located on left side of engine compartment, between Power Distribution Center (PDC) and Transmission Control Module (TCM). See Figure. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance between terminal No. 1 (Gray/Red wire) and terminals No. 2 (Yellow/Black), No. 3 (Brown/White wire) and No. 4 (Violet/Black wire) at IAC motor harness connector. See Fig 1. If all resistance readings are 5 ohms or more, go to next step. If any resistance reading is less than 5 ohms, Gray/Red wire is shorted to wire with resistance less than 5 ohms. Repair wiring as necessary.
  7. Measure resistance between terminal No. 2 (Yellow/Black wire) and terminals No. 3 (Brown/White wire) and No. 4 (Violet/Black wire) at IAC motor harness connector. If any resistance reading is less than 5 ohms, Yellow/Black wire is shorted to wire with resistance less than 5 ohms. Repair wiring as necessary. If all resistance readings are 5 ohms or more, go to next step.
  8. Measure resistance between terminals No. 3 (Brown/White wire) and No. 4 (Violet/Black wire) at IAC motor harness connector. If resistance is less than 5 ohms, Brown/White and Violet/Black wires are shorted together. Repair wiring as necessary. If all resistance is 5 ohms or more, go to next step.
  9. At this time, IAC motor is assumed to be defective. Replace IAC motor.
  10. Turn ignition off. Ensure IAC motor is disconnected. Turn ignition off. Ensure IAC motor is disconnected. Disconnect PCM connectors. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance of Violet/Black wire between terminals No. 4 at IAC motor harness connector and No. 58 at PCM C2 harness connector. See Figure and Fig 1 . If resistance is 5 ohms or more, repair open in Violet/Black wire. If resistance is less than 5 ohms, go to next step.
  11. Measure resistance between ground and terminal No. 4 (Violet/Black wire) at IAC motor harness connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in Violet/Black wire between IAC motor and PCM.
  12. At this time, PCM is assumed to be defective. Replace PCM.
  13. Turn ignition off. Ensure IAC motor is disconnected. Disconnect PCM connectors. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance of Brown/White wire between terminals No. 3 at IAC motor harness connector and terminal No. 48 at PCM C2 harness connector. See Figure and Fig 1 . If resistance is 5 ohms or more, repair open in Brown/White wire. If resistance is less than 5 ohms, go to next step.
  14. Measure resistance between ground and terminal No. 3 (Brown/White wire) at IAC motor harness connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in Brown/White wire between IAC motor and PCM.
  15. At this time, PCM is assumed to be defective. Replace PCM.
  16. Turn ignition off. Ensure IAC motor is disconnected. Disconnect PCM connectors. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance of Yellow/Black wire between terminals No. 2 at IAC motor harness connector and No. 49 at PCM C2 harness connector. See Figure and Fig 1 . If resistance is 5 ohms or more, repair open in Yellow/Black wire. If resistance is less than 5 ohms, go to next step.
  17. Measure resistance between ground and terminal No. 2 (Yellow/Black wire) at IAC motor connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in Yellow/Black wire between IAC motor and PCM.
  18. At this time, PCM is assumed to be defective. Replace PCM.
  19. Turn ignition off. Ensure IAC motor is disconnected. Disconnect PCM connectors. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance of Gray/Red wire between terminals No. 1 at IAC motor harness connector and No. 57 at PCM C2 harness connector. See Figure and Fig 1 . If resistance is 5 ohms or more, repair open in Gray/Red wire. If resistance is less than 5 ohms, replace PCM.
  20. Measure resistance between ground and terminal No. 1 (Gray/Red wire) at IAC motor harness connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in Gray/Red wire between IAC motor and PCM.
  21. At this time, PCM is assumed to be defective. Replace PCM.
  22. Visually inspect wiring harness and connectors between IAC motor and PCM. Repair connectors and wiring harness as necessary. If connectors and wiring harness are okay, reconnect all connectors and go to next step.
  23. Start engine and allow it to idle. Using scan tool, go to SYSTEM TESTS and select IAC WIGGLE TEST. While monitoring IAC motor operation, wiggle wiring harness from IAC motor to PCM. If IAC motor stops operating at any time while wiggling wiring harness, repair wiring harness where wiggling caused IAC motor to stop operating. If IAC motor does not stop operating at any time while wiggling wiring harness, no problem is indicated at this time. Test is complete.
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