Idle Speed Control System

Idle Speed Control System:

CIRCUIT OPERATION
The idle speed is controlled by the amount of air that is allowed to bypass the throttle plate through the auxiliary air control (AAC) valve. The AAC valve is turned ON and OFF at a rate between 100 and 200 Hz. The ECU calculates the duty cycle (frequency of ON/OFF signals) necessary to maintain the proper idle speed, compensating for transmission gear position, electrical and accessory loads.

IACV-Auxiliary Air Control Valve:

AUXILIARY AIR CONTROL VALVE
The auxiliary air control (AAC) valve controls the idle speed. It receives a pulse signal from the ECU which opens and closes an air passage allowing a precise amount of air to bypass the throttle plate.