Idle Air Control (IAC) Valve

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 articles may refer to Tech 1 tester, General Motor's bidirectional tester.
- 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: IAC Valve Circuit ID (Typical)

Courtesy of GENERAL MOTORS CORP.