See Figure 41. Idle Air Control (IAC) valve is located at right side of engine compartment, under engine top cover.
See Figure 42. IAC valve maintains idle speed at approximately 900 RPM. IAC valve winding resistance is 6.7 to 8.7 ohms at 68°F (20°C).At idle, the engine receives air only via the idle air control valve. Engine Control Module (ECM) controls the degree of valve opening to keep idle speed constant. The valve opens slightly more when the A/C compressor is switched on, or if DRIVE has been selected on an automatic transmission, in order to compensate idle speed, which would otherwise fall.
IAC valve is a single-coil type and supplied with power from the main relay. It is controlled from ECM pin 49 by pulse width modulation frequency of 500 Hz. IAC valve opens more the longer the control module keeps pin 49 grounded. ECM is programmed to maintain engine idling speed at 850 to 950 RPM. Rapid changes in idling speed cannot be compensated for by changing the flow of air. Instead, ignition timing is modulated so that engine idle speed is maintained constant. If there is an open circuit to the idle air control valve, a spring sets valve opening so that idle speed is at least 1000 RPM when engine is warmed up.
Removal & Installation
See Figure 43. Remove engine top cover and disconnect IAC valve electrical connector and vacuum hoses. Remove valve from brackets.
To install, reverse removal procedure and ensure IAC valve is positioned correctly.
- DTC P0506 will be set if idle speed is too high.
- DTC P0507 will be set if idle speed is too low.
- Clear all DTCs after completing their diagnoses. Perform final drive cycle under varying engine loads and speeds for 5 minutes. Evaluate drive cycle and confirm that DTCs have not reset.