Chart C-2, Idle Air Control (IAC) Valve Check: Notes

Fig 1: Chart C-2, Wiring Diagram Idle Air Control (IAC) Valve Check

NOTE: Test numbers refer to test numbers on diagnostic charts.

1. Continue with test, even if engine will not idle. If idle is too low, data ED22 will display 80 or more counts, or steps. If idle is high, it will display zero counts. Occasionally an erratic or unstable idle may occur. If engine speed varies 200 RPM or more (up and down), disconnect IAC. If condition is unchanged, IAC is not at fault.
2. When engine was stopped, IAC valve is retracted (more air) to a fixed "Park" position for increased airflow and idle speed, during next engine start. Data ED22 will display 100 or more counts.
3. Ensure that IAC valve is unplugged prior to this test. Test light will confirm ECM signals by a steady or flashing light on all circuits.
4. There is a remote possibility that one of the circuits is shorted to voltage, which would have been indicated by a steady light. Unplug ECM and turn ignition on. Probe terminals to check for this condition.