Camshaft Actuator System
Camshaft Actuator System Description
Camshaft Position Actuator System
The camshaft position actuator system is an electro-hydraulic operated device used for a variety of engine performance and operational enhancements. These enhancements include lower emission output through exhaust gas dilution of the intake charge in the combustion chamber, a broader engine torque range, and improved fuel economy. The camshaft position actuator system accomplishes this by, changing the angle or timing of the camshaft, relative to the crankshaft position. The camshaft position actuator simply allows earlier or later intake and exhaust valve opening, during the four stroke engine cycle. The camshaft position actuator cannot vary the duration of valve opening, or the valve lift.
During engine OFF, engine idling, and engine shutdown conditions, the camshaft actuator is held in the park position. Internal to the camshaft position actuator assembly is a return spring and a locking pin. During non-phasing modes of the camshaft, the return spring rotates the camshaft back to the park position, and the locking pin retains the camshaft position actuator sprocket to the camshaft. The engine control module (ECM) can only command the camshaft position actuator to retard the valve timing from the park position, or advance the valve timing back to the park position.
Camshaft Position Actuator System Operation
The camshaft position actuator system is controlled by the engine control module (ECM). The ECM sends a pulse width modulated, 12 V signal to the camshaft position actuator solenoid to control the amount of pressurized engine oil, into the camshaft position actuator. A low reference circuit, or ground wire between the camshaft position actuator solenoid and the ECM completes the electrical circuit. The frequency of the pulse width modulated signal is fixed at 150 Hz. To regulate the pressurized engine oil into the camshaft position actuator, the solenoid uses electromagnetic force on the solenoid pintle to pulse the oil control spool valve. The pressurized engine oil is sent to unseat the locking pin, and to the vane and rotor assembly of the camshaft position actuator, to either retard or advance the valve timing. The ECM will control the amount of ON time applied to the solenoid, through the 12 V signal from the ECM.
The ECM uses the following inputs to calculate the optimum valve timing before assuming control of the camshaft position actuator:
* Engine speed
* Manifold absolute pressure
* Throttle position angle
* Camshaft position sensor
* Crankshaft position sensor
* Crankshaft/camshaft correlation
* Engine coolant temperature
* Closed loop fuel control
* Engine oil pressure
* Engine oil level
* Camshaft position actuator solenoid circuit state
Camshaft Position Actuator Solenoid Circuit Diagnostics
The engine control module (ECM) monitors the control circuit of the camshaft position actuator solenoid for electrical faults. The control module has the ability to determine if a control circuit is open, shorted high, or shorted low. If the control module detects a fault with the camshaft position actuator solenoid control circuit, DTC P0010 will set.
Camshaft Position Actuator System Performance Diagnostic
The engine control module (ECM) monitors the performance of the camshaft position actuator system by monitoring the calibrated desired position, and the actual position of the camshaft, through the 4X signal of the camshaft position sensor. If the difference between the actual and desired position is greater than a calibrated angle, for more than a calibrated amount of time, DTC P0011 will set.
For the system descriptions covering the hydraulic/mechanical part of the camshaft position actuator, refer to Camshaft Position Actuator and Solenoid Valve Description (Description and Operation).