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DTC P0509: IAC Motor Sense Circuit High: Testing

  1. Start engine and let it idle. If engine will not idle, hold engine speed between 800 and 1500 RPM. Using scan tool, read IAC CURRENT. If IAC CURRENT is more than 999 milliamps, go to next step. If IAC CURRENT is 999 milliamps or less, go to step  7 .
  2. Turn ignition off. Disconnect IAC motor harness connector located on top of throttle body. Turn ignition on. If IAC CURRENT is more than zero milliamps, go to next step. If IAC CURRENT is zero milliamps, replace IAC motor.
  3. Turn ignition off. Measure resistance between IAC motor harness connector terminals. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short between IAC motor sense circuit and IAC motor driver circuit.
  4. Turn ignition on. Using scan tool, actuate Automatic Shutdown (ASD) relay. Measure voltage between ground and IAC motor sense circuit (Brown/White wire) at IAC motor harness connector. If voltage is .5 volt or less, go to next step. If voltage is more than .5 volt, repair short to voltage in IAC motor sense circuit.
  5. With ASD relay actuated, measure voltage between ground and IAC motor driver circuit (Yellow/Black wire) at IAC motor harness connector. If voltage is .5 volt or less, go to next step. If voltage is more than .5 volt, repair short to voltage in IAC motor driver circuit.
  6. If no other possible causes are remaining, replace PCM.
  7. Conditions that set DTC are not present at this time. Perform the following to help identify intermittent condition:
    • With engine running at normal operating temperature, wiggle related wiring harness while monitoring related parameters on scan tool. If voltage changes or DTC sets while wiggling wiring harness, repair connectors or wiring harness where wiggling caused voltage to change or DTC to set.
    • Review freeze frame information on scan tool. Duplicate conditions present when DTC was set.
    • Refer to any Technical Service Bulletins (TSBs) that may apply.
    • Visually inspect related wiring harness. Check for chafed, pierced, pinched or partially broken wires.
    • Visually inspect related wiring harness connectors. Check for broken, bent, pushed out or corroded terminals.

    If a problem is found, repair as necessary. If no problems are found, test is complete.

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