Diagnostic Aids

NOTE: For wiring diagrams, see WIRING DIAGRAMS .

Any condition that can affect engine performance at idle, can affect the performance of the IAC system. A careful visual and/or physical inspection of the engine is necessary when the scan tool indicates that the engine speed or the IAC Motor Command readings are out of range.

A warm engine that is idling too slow, with a high IAC Motor Command of 50 percent or more, may have an open in the ignition positive voltage circuit to terminal No. 5.

A warm engine that is idling too fast, with a low IAC Motor Command of 15 percent or less, may have an open in the ignition positive voltage circuit to terminal No. 2.

An intermittent IAC system concern may be caused by poor electrical connections in the IAC valve circuits. Thoroughly check any circuitry that is suspected of causing an intermittent condition.