It regulates the amount of air bypassing the control of the throttle plate. As engine loads and ambient temperatures change the engine rpm changes. A pintle on the Idle Air Control (IAC) stepper motor protrudes into a passage in the throttle body, controlling air flow through the passage. The IAC is controlled by the Powertrain Control Module (PCM) to maintain the target engine idle speed.
The IAC motor has 4 wires with 4 circuits. Two of the wires are for 12 volts and ground to supply electrical current to the motor windings to operate the stepper motor in one direction. The other 2 wires are also for 12 volts and ground to supply electrical current to operate the stepper motor in the opposite direction.
To make the IAC go in the opposite direction, the PCM just reverses polarity on both windings. If only 1 wire is open, the IAC can only be moved 1 step (increment) in either direction. To keep the IAC motor in position when no movement is needed, the PCM will energize both windings at the same time. This locks the IAC motor in place.
In the IAC motor system, the PCM will count every step that the motor is moved. This allows the PCM to determine the motor pintle position. If the memory is cleared, the PCM no longer knows the position of the pintle. So at the first key ON, the PCM drives the IAC motor closed, regardless of where it was before. This zeros the counter. From this point the PCM will back out the IAC motor and keep track of its position again.
Removal & Installation
3.7L & 4.7L Engines
- Before servicing the vehicle, refer to the Precautions Section.
- Remove air resonator box at throttle body.
- Disconnect the electrical connector from the Idle Air Control (IAC) motor.
- Remove the two mounting screws.
- Remove IAC motor from throttle body.
- Install IAC motor to throttle body.
- Install and tighten the two mounting screws to 60 in. lbs. (7 Nm).
- Install the electrical harness connector.
- Install air resonator to the throttle body.
- Turn the ignition on.
- Install a scan tool.
- With a scan tool, select view DTCs. record DTC and freeze frame information.
- Start the engine and allow it to idle for at least 60 seconds.
- With a scan tool, select view DTCs. If no DTCs are present problem may be intermittent.
- If a DTCs is present turn the ignition off.
- Disconnect the IAC Motor harness connector.
- Remove the IAC Motor.
- Inspect the IAC air passages for restrictions and damage to the IAC motor.
- Measure the resistance across the IAC Motor pin terminals (component side).
- The resistance should read approximately 9.7 +/- 1.0 ohms.
If the readings are not as stated replace the IAC motor.