The Idle Air Control (IAC) valve controls the engine idle speed and dashpot functions. The valve is located on the side of the throttle body. This valve allows the necessary amount of air, as determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed.
NOTE: Due to the diode in the solenoid, place the ohmmeter positive lead on the VPWRterminal and the negative lead on the ISC terminal.
The following symptoms can be caused by a faulty IAC due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit.