Camshaft Position Actuator System Operation

More than one camshaft position actuator may be used, depending on the number of camshafts and camshaft configuration. Camshaft actuators are designed to advance or retard camshaft timing from the base timing, depending on the application. Typically, intake cam timing is advanced, and exhaust timing is retarded to achieve desired results.

Camshaft position actuator solenoid valves have three duty cycle ranges controlling the relative position between the camshaft position actuator outer sprocket and the inner rotor. From 0 to 40% duty cycle, oil is vented from apply chambers while oil pressure is applied to the opposite chambers returning camshaft timing toward base timing. At 40-55% duty cycle, the solenoid valve moves to a hold position, closing both actuator chamber passages, preventing oil flow in or out of any chambers. From 55 to 100% duty cycle, oil pressure is applied to the apply chambers, and vented from the opposite chambers, to move camshaft timing away from base timing.

During operation, the ECM may require camshaft timing to be advanced or retarded from base timing. In the event of a camshaft timing change, the ECM drives the camshaft position actuator solenoid valve duty cycle above 55%, or below 40%, for a brief time period until camshaft sensors indicate the desired timing change. Once the desired timing is achieved, the ECM returns the solenoid valve duty cycle to 40 to 55%, closing both actuator chamber passages, holding the actuator in the adjusted position.