Idle Air Control (IAC) Valve

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

Disconnect harness connector to motor. Check resistance across IAC coil terminals "A" to "B" and "C" to "D". See Fig 1. Resistance should be 40-80 ohms. If okay, go to next step. If resistance is not as specified, replace IAC valve.
Check resistance between IAC terminals "B" to "C" and "A" to "D". Resistance should be infinite. If resistance is not as specified, replace IAC valve.
NOTE: Functional testing of Idle Air Control (IAC) valve requires a scan tester capable of cycling ECM output devices (bidirectional) or a special IAC Driver and Noid Light Set (222L or J-37027). Flow charts in appropriate TESTS W/CODES article may refer to Tech 1 tester, General Motor's bidirectional tester. See CODE 35 chart in appropriate TESTS W/CODES article for further IAC testing.
- G - TESTS W/CODES - 4.3L
- G - TESTS W/CODES - 5.0L
- G - TESTS W/CODES - 5.7L
- G - TESTS W/CODES - 7.4L

Fig 1: Identifying IAC Valve Circuits (Typical)

Courtesy of GENERAL MOTORS CORP.