DTC P0506: Idle Speed Low: Description

WARNING: This page is about a different variant/trim than selected.

Idle Air Control (IAC) valve consists of a movable pintle driven by a gear attached to an electric motor, which is called a stepper motor. IAC valve motor is a 2-phase bi-polar permanent magnet stepper motor that is capable of highly accurate rotation or movement every time polarity of a winding is changed. You see this change in polarity when you observe a test light connected between ground or battery voltage and an IAC valve circuit while Powertrain Control Module (PCM) is attempting to change engine RPM. Test light will flash on or off each time polarity is changed.

PCM does not use a physical sensor to determine IAC valve pintle position. PCM uses a predicted number of counts. One count represents one change in polarity, which equals one step of stepper motor. PCM counts steps that have been commanded to determine IAC pintle position. PCM uses IAC valve to control engine idle speed by changing pintle position in idle air passage of throttle body. This varies airflow around throttle plate when the throttle is closed.

To determine desired position of IAC valve pintle during idle or during deceleration, PCM refers to the following inputs:

Engine RPM.
Battery voltage.
Air temperature.
Engine Coolant Temperature (ECT).
Throttle position sensor angle.
Engine load.
Vehicle speed.

When ignition key is turned off an ignition cycle, PCM will seat IAC valve pintle in the air by-pass bore then retract the pintle a predetermined amount of counts. This retraction allows proper amount of air to by-pass the throttle plate for engine to start. This procedure is known as an IAC Reset.