Idle Air Control (IAC) Valve
The IAC valve, mounted on the throttle body, controls idle speed by regulating throttle plate by-pass air. IAC valve includes an air by-pass valve and idle speed control solenoid valve. The air by-pass valve is affected by the engine coolant temperature and functions during cold engine conditions less than 122 F (50 C). The idle speed control solenoid is controlled by PCM and works throughout the entire temperature range.
On some models, idle is controlled by idle speed control air by-pass valve. A throttle air by-pass valve is a solenoid-operated valve controlled by PCM. The valve allows air to by-pass throttle plates to control cold engine fast idle, no-touch start, dashpot, overtemperature idle boost and engine load idle correction.
Air by-pass channel carries idle airflow regulated by air by-pass valve. Air by-pass valve is controlled by PCM to adjust both cold and warm idle speeds. Air by-pass valve uses solenoid valve to vary idle airflow volume allowed to enter engine
Idle Air Control (IAC) Solenoid
Solenoid is by-pass air type. Ensure ignition is off. Disconnect IAC solenoid harness connector. Set DVOM to 200-ohm scale. Measure resistance between IAC solenoid connector terminals. See Fig. 3 . Solenoid has diode. Connect DVOM (+) test lead to terminal VPWR and DVOM (-) lead to terminal IAC.
Resistance should be 6-13 ohms. If resistance is not as specified, replace solenoid. Faults in IAC solenoid or circuit should set a service code. See QUICK TEST in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section. If no service code has been set, see CIRCUIT TEST KE in appropriate TESTS W/CODES article for additional testing and specifications.
Saturday, November 15th, 2008 AT 7:18 AM