Idle Speed Control: Function

The idle air control valve utilizes two coils that use opposing pulse width modulated (PWM) signals to control the position of a rotary valve. If one of the circuits that supplies the PWM signal fails, the ECM closes down the remaining signal preventing the idle air control valve from working at its maximum/minimum setting. If this should occur, the idle air control valve assumes a default idle position at which the engine idle speed is raised to 1200 rev/min with no load placed on the engine.