CMP Actuator System Operation

The engine control module (ECM) sends an electrical signal to the camshaft position (CMP) actuator solenoids through the control circuits when a camshaft timing change is desired. The ground circuit of the CMP actuator solenoid is used as a return. The CMP actuator solenoid uses electromagnetic force to pull on the plunger of the oil control valve. The oil control valve will port the pressurized engine oil to either the advancing or retarding chambers of the CMP actuator. The CMP actuator, in turn, changes the camshaft position relative to crankshaft position. The ECM uses the CMP sensors to determine the position of the camshafts.

The ECM calculates the optimum CMP through the following inputs:

• Engine speed
• Manifold absolute pressure (MAP)
• Throttle position indicated angle
• Crankshaft position (CKP)
• CMP
• Engine load
• Barometric pressure (BARO)

The ECM monitors the following inputs before assuming control of the CMP actuator system:

• Engine coolant temperature (ECT)
• Loop status
• Calculated engine oil temperature (EOT)
• Engine oil pressure (EOP)
• Engine oil level
• Crankshaft/camshaft correlation
• Ignition 1 signal voltage
• Barometric pressure (BARO)