Idle Air Control (IAC) Valve

1998 Chevrolet Tracker 2D Utility, RWD, AutomaticSECTION Idle Air Control (IAC) Valve
  1. Check idle speed following procedures in ADJUSTMENTS article. If idle speed is as specified, go to next step. If idle speed is not as specified, follow procedures in DTC P0505 in TESTS W/CODES article.
  2. With engine running, turn headlights on. If idle remains at specified idle speed, system is okay. If idle speed is not within specification, go to next step.
  3. Turn ignition off. Disconnect IAC valve hose from air intake pipe. Turn ignition on. Blow through end of hose and ensure air does not pass through valve. Turn ignition off. On models with 3-speed automatic or manual transmission, connect a fused jumper wire (backprobe) between PCM harness connector "B" terminal No. 12 (Light Green/Black wire) and ground. See Figure . On models with 4-speed automatic transmission, connect a fused jumper wire (backprobe) between PCM harness connector "A" terminal No. 12 (Light Green/Black wire) and ground. See Figure . Turn ignition on. Blow through end of hose and ensure air passes through valve. If operation is not as specified, go to next step. If operation is as specified, replace PCM. Retest system.
  4. Turn ignition off. Disconnect IAC valve harness connector. Using an ohmmeter, measure resistance between terminals of IAC valve. If resistance is 11-14 ohms at 68°F (20°C), go to next step. If resistance is not as specified, replace IAC valve. Retest system.
  5. Blow into disconnected IAC valve hose. Ensure air does not pass through. Using fused jumper wires, connect battery voltage and ground to IAC valve terminals. Air should now pass through valve. If operation is not as specified, replace IAC valve. If IAC valve is okay, check IAC valve harness for open or short. Repair as necessary.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.