Idle Control System: Notes

Idle speed is controlled by ECM through IACV-AAC. ECM controls idle speed components based upon signals received from various input devices. If idle speed components test correctly but idle speed is not being regulated properly, check input signals to ECM. See IDLE SPEED SYSTEM INPUT SIGNALS table.

On Q45, fast idle is controlled by fast idle cam on non-traction control system equipped vehicles and air cut valve on traction control system equipped vehicles. Engine coolant temperature changes volume of wax element to control amount of air by-passing secondary throttle valve. As engine warms, by-pass air is reduced, reducing idle speed.