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DTC P0509: IAC Valve Sense Circuit High: Testing

  1. Start the engine. Allow the engine to idle. If the engine will not idle, maintain an engine speed between 800 and 1500 RPM. With the DRBIII®, read the IAC Current. Is the IAC Current above 999 mA? 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®, monitor the IAC Current. Turn the ignition on. Does the DRBIII® display IAC Current at 0 mA? If yes, replace the IAC Motor. If no, go to next step.
  3. With the DRBIII®, actuate the ASD Relay. Measure the voltage of the IAC Motor Sensor circuit in the IAC Motor harness connector. If the voltage above 0.5 volt? If yes, repair the short to voltage in the IAC Motor Sense circuit. If no, go to next step.
  4. With the DRBIII®, actuate the ASD Relay. Measure the voltage of the IAC Motor Driver circuit in the IAC Motor harness connector. If the voltage above 0.5 volt? If yes, repair the short to voltage in the IAC Motor driver circuit. If no, go to next step.
  5. Turn the ignition off. Measure the resistance between the IAC Motor harness connector. Is the resistance below 5.0 ohms? If yes, repair the IAC Motor Sense circuit short to the IAC Motor Driver circuit. If no, go to next step.
    6. NOTE: Before continuing, check the PCM harness connectors for corrosion, damage or terminal push out. Repair as necessary.
  6. There are no possible causes remaining, replace PCM. Program the new PCM. See PROGRAMMING .
    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. The conditions that set the DTC are not present at this time. The following may help in identifying the intermittent condition. With the engine running at normal operating temperature, monitor the DRBIII® 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® Freeze Frame information. If possible, try to duplicate the conditions under which the DTC was set. Refer to any Technical Service Bulletins (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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