Auto Repair Q&A



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Resetting the AIC with IAR on most vehicles with erratic idle

Ignition coils

On most vehicles with a fuel injected engine that is showing symptoms of erratic idle, a reset of the air idler control (AIC) can remedy the situation. Or at least help rule out some issues for diagnostic purposes.

The procedure for resetting the AIC is generally the same on most vehicles, though some may have somewhat different methods than others. The following will at least get you going as to how to undergo a reset.

The key to an AIC reset is to go through the Idle Air Relearn (IAR) procedure to zero out the data coming from the sensors. The IAR is there specifically to reset after changing out an oxygen or temperature sensor.

With the vehicle at full operating temperature. All electrical accessories should be turned off, including lights and air conditioning. Shut off the engine and wait for ten seconds, then turn the key to the "on" position without starting it again. Wait for three seconds, then press the gas pedal all the way down, then release, then press, then release for a total of five times. Then hold the accelerator pedal down for seven seconds. The engine service light will begin to blink.

Keep the accelerator pedal down for another ten seconds and the engine light should stop blinking. When it does, release the accelerator pedal. Start the engine.

The idle should go up to its lowest point and the engine should be at operating temperature (or very close to it). Resting idle should be at 700-800 rpm. Revving the engine a few times will increase rpm and immediately drop it back to 700-800 when the pedal is released.

If all other problems have been resolved, the car should operate normally.