GMC 19333272 Idle Speed Control

The idle speed of the engine is controlled by the Idle Control Valve (ICV), which is regulated by the ECM/PCM. The ICV adjusts the air bypassing the throttle plate to maintain the idle speed based on various engine conditions. The idle speed is not adjustable on these models. To test the ICV, a scan tool is required, but there are limited tests that can be performed by a home mechanic to verify its operation. When starting cold, the ICV should change the idle as it warms up. If there are any signs of ICV failure or if the engine stumbles or stalls, further testing will be necessary. Disconnect the electrical connector from the ICV and measure resistance across its terminals. Replace the ICV if an open circuit is detected. When operating correctly, then a qualified repair shop should diagnose the ECM/PCM for replacement of the ICV. Remove all needed components and access the ICV by disconnecting the electrical connector and removing it from the throttle body in order to replace it. Inspect and clean both if necessary; I had cleaned it while inspecting it also. During the installation of a new one, measure the pintle tip to mounting flange distance and adjust if needed. Install with a new O-ring being lubricated before securely tightening the valve onto place. Cycle the ignition key so as to reset it before starting an engine again to check idle operation.