System Description

IDLE AIR CONTROL VALVE (IACV) - AUXILIARY AIR CONTROL (AAC) VALVE (DTC: P0505)
This system automatically controls engine idle speed to a specified level. Idle speed is controlled through fine adjustment of the amount of air which bypasses the throttle valve via Idle Air Control Valve - Auxiliary Air Control (IACV-AAC) valve. The IACV AAC valve opens and closes according to the signal sent from the Engine Control Module (ECM). The camshaft position sensor detects the actual engine speed and sends a signal to the ECM. The ECM then controls the IACV-AAC valve so that engine speed coincides with the target value memorized in ECM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the ECM is determined by taking into consideration various engine conditions, such as during warm up, deceleration, and engine load (air conditioner, power steering and cooling fan operation).