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DTC P0509: IAC Motor Sense Circuit High: Testing

NOTE: If the engine will not idle, maintain an engine speed 800-1500 RPM.
  1. Start the engine. Allow the engine to idle. With the DRBIII(R), read the IAC current. Is the IAC current more than 999 milliamps? If yes, go to next step. If no, go to step  7 .
  2. Turn the ignition off. Disconnect the IAC motor harness connector. With the DRBIII(R), monitor the IAC current. Turn the ignition on. Does the DRBIII(R) display IAC current at zero milliamps? If yes, replace the IAC motor. If no, go to next step.
  3. Turn the ignition off. Measure the resistance across the IAC motor harness connector. Is the resistance less than 5.0 ohms? If yes, repair the IAC motor sense circuit shorted to the IAC motor driver circuit. If no, go to next step.
  4. Turn the ignition on. With the DRBIII(R), actuate the Auto Shutdown (ASD) relay. Measure the voltage on the IAC motor sense circuit in the IAC motor harness connector. Is the voltage more than 0.5 volt? If yes, stop all actuations and repair the IAC motor sense circuit for a short to voltage. If no, stop all actuations and go to next step.
  5. With the DRBIII(R), actuate the ASD relay. Measure the voltage on the IAC motor driver circuit in the IAC motor harness connector. Is the voltage more than 0.5 volt? If yes, stop all actuations and repair the IAC motor driver circuit for a short to voltage. If no, stop all actuations and go to next step.
  6. There are no possible causes remaining, replace PCM.
    7. WARNING: When the engine is operating, DO NOT stand in a direct line with the fan. DO NOT put your hands near the pulleys, belts or fan. DO NOT wear loose clothing.
  7. Conditions that set DTC are not present at this time. The following list may help in identifying the intermittent condition:
    • With the engine running at normal operating temperature, monitor the DRBIII(R) parameters related to the DTC while wiggling the wiring harness. Look for parameter values to change and/or a DTC to set.
    • Review the DRBIII(R) Freeze Frame information to identify under what conditions the DTC set.
    • Refer to any Technical Service Bulletin (TSB) that may apply.
    • Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.
    • Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.

      Were any of the above conditions present? If yes, repair as necessary. If no, test is complete.

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