CMP Actuator System Operation

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The camshaft position (CMP) actuator system is controlled by the engine control module (ECM). The ECM sends a pulse width modulated, 12-volt signal to the CMP actuator solenoid to control the amount of pressurized engine oil, into the CMP actuator. A low reference circuit, or ground wire between the CMP 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 CMP 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 CMP 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-volt signal from the ECM.

The ECM uses the following inputs before assuming control of the CMP actuator, and to calculate the optimum valve timing.

Engine speed
Manifold absolute pressure (MAP)
Throttle position angle
Camshaft position sensor (CMP)
Crankshaft position sensor (CKP)
Crankshaft/camshaft correlation
Engine coolant temperature (ECT)
Closed loop fuel control
Engine oil pressure (EOP)
Engine oil level
CMP actuator solenoid circuit state