C 2500 Truck 2WD V8-5.7L VIN R (1997)
Idle Speed/Throttle Actuator - Electronic: Testing and Inspection
If the Idle Air Control (IAC) valve is disconnected or connected when the engine is running, the idle RPM may be wrong. The IAC valve may be reset
by turning the ignition switch ON for 10 seconds, OFF for 5 seconds. The IAC valve affects the idle characteristics of the engine as well as throttle
follow-up to compensation for sudden throttle closing. If it is open fully too much air will be allowed in the manifold and idle speed will be high. If it is
stuck closed, too little air will be allowed in the manifold, and idle speed will be too low. If it is stuck part way open, the idle may be rough, and will not
respond to engine load changes.
The diagnosis of Idle Air Control (IAC) can be found in VCM Outputs Diagnosis. See: Computers and Control Systems/Testing and Inspection
