Idle Speed/Throttle Actuator - Electronic: Description and Operation

IAC Valve Operation And Fuel Pressure Regulation:

Engine idle speeds are controlled by the control module through the Idle Air Control (IAC) valve mounted on the throttle body. The control module sends voltage pulses to the IAC motor windings causing the IAC motor shaft to move in and out a given distance for each pulse, (referred to as IAC counts on a scan tool). This movement controls airflow around the throttle plates, which in turn, controls engine idle speed, either cold or hot. IAC valve pintle position counts can be seen by using a Scan tool. 0 counts corresponds to fully closed passage, while 140 counts or more (depending on application) corresponds to full flow.