Idle Speed/Throttle Actuator - Electronic: Description and Operation

IAC/TPS Removal:

PURPOSE
The Idle Air Control (IAC) motor maintains optimum idle speed under varying engine loads and prevents deceleration die out.

OPERATION
The IAC motor controls air flow through an air passage in the throttle body. The Powertrain Control Module (PCM) controls engine idle speed by adjusting the IAC motor to compensate for engine load or ambient conditions.

The IAC varies the amount of air that is allowed to bypass the throttle blades. It does this by extending or retracting the IAC pintle into the idle air passage. The further the IAC pintle protrudes into this passage the slower the idle speed and the less the IAC pintle protrudes the greater the idle speed.

The PCM calculates proper idle speed using information from throttle position, vehicle speed, and engine coolant temperature sensors and brake and neutral/safety switches.

NOTE: A (factory adjusted) set screw is used to mechanically limit the position of the throttle plate. NEVER attempt to adjust idle speed using this screw.

CIRCUIT OPERATION
The Powertrain Control Module (PCM) operates the Idle Air Control (IAC) motor through 4 circuits - K39, K40, K59, and K60. Each circuit connects to separate cavities in the PCM connector.
- Circuit K39 connects to cavity 39 of the PCM connector.
- Circuit K40 connects to cavity 40 of the PCM connector.
- Circuit K59 connects to cavity 59 of the PCM connector.
- Circuit K60 connects to cavity 60 of the PCM connector.