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DTC P0508: IAC Valve Signal Circuit Low: Testing

WARNING: This page is about a different car, the 2003 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start the engine. Allow the engine to idle. If the engine will not idle, maintain an engine speed between 800-1500 RPM. Check for vacuum leaks, proper PCV valve installation, proper MAP sensor installation, and proper IAC installation. With the DRBIII® scan tool, read the IAC current. Is the IAC current below 146 mA? If yes, go to next step. If no, see INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn the ignition off. Disconnect the IAC motor harness connector. Remove the IAC motor. Inspect the IAC air passages for restriction and damage to the IAC valve. Measure the resistance across the IAC motor pin terminals (component). Is the resistance 8.7-10.7 ohms? If yes, go to next step. If no, replace the IAC Motor.
    3. CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool (8815) to perform diagnosis.
  3. Disconnect the PCM harness connectors. Measure the resistance of the (K60) IAC signal circuit from the IAC motor harness connector to the appropriate terminal of Miller Special Tool (8815). Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair the open in the (K60) IAC signal circuit.
  4. Measure the resistance between ground and the (K60) IAC signal circuit in the IAC motor harness connector. Is the resistance below 100 ohms? If yes, repair the short to ground in the (K60) IAC signal circuit. If no, go to next step.
    5. CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool (8815) to perform diagnosis.
  5. Measure the resistance of the (K39) IAC control circuit from the IAC motor harness connector to the appropriate terminal of Miller Special Tool (8815). Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair the open in the (K39) IAC control circuit.
  6. Measure the resistance between ground and the (K39) IAC control circuit in the IAC motor harness connector. Is the resistance below 100 ohms? If yes, repair the short to ground in the (K39) IAC control circuit. If no, go to next step.
    7. NOTE: Before continuing, disconnect the PCM harness connectors and check the related wiring terminals for corrosion, damage or terminal push out. Repair as necessary.
  7. Using the wiring diagram as a guide, inspect the wire harness and connectors. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect both the component and the PCM connectors. Pay particular attention to all power and ground circuits. If there are no possible causes remaining, replace and program the PCM. See PROGRAMMING .
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