1993 Geo Tracker LSi, AutomaticFACTORY OEM SERVICE PROCEDURE

Idle Air Control Valve

  1. With ignition off, disconnect electrical connector from Idle Air Control (IAC) valve. IAC valve is located on throttle body and contains a Blue/Black and Light Green/Black wire connector.
  2. Turn ignition on. Using voltmeter, check for battery voltage at Blue/Black wire of electrical connector. Battery voltage should exist.
  3. If battery voltage exists, go to next step. If battery voltage does not exist, check for open circuit in Blue/Black wire between IAC valve and EFI main relay. EFI main relay is mounted on ECM, located under left side of instrument panel, near kick panel. See Figure .
  4. Turn ignition off. Connect test light to battery voltage. Probe Light Green/Black wire. Turn ignition on. Light should glow momentarily.
  5. If test light glows momentarily, go to next step. If test light stays on, check for short to ground in Light Green/Black wire between IAC valve and ECM. ECM is located under left side of instrument panel, near kick panel. If test light does not glow momentarily, check for open circuit in Light Green/Black wire between IAC valve and ECM. If circuit is not open, replace ECM.
  6. Turn ignition off. Using ohmmeter, measure resistance between IAC valve terminals. Resistance should be 11-14 ohms at 68°F (20°C).
    CAUTION: DO NOT  apply battery voltage to IAC solenoid for more than one second. Allow 10 seconds between voltage applications to prevent valve damage.
  7. If resistance is not as specified, replace IAC valve. If resistance is as specified, connect battery voltage to Blue/Black wire terminal and ground Light Green/Black wire terminal momentarily. A click should be heard to indicate valve operation. Replace IAC valve if a click is not heard. Reinstall electrical connector.
NOTE: Idle-up vacuum switching valve also may be referred to as Idle Speed Control (ISC) solenoid.
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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.

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