Cobalt L4-2.4L VIN B (2006)
Variable Induction Control Actuator: Description and Operation
CMP ACTUATOR SYSTEM OPERATION
The camshaft position (CMP) actuator system is controlled by the control module. The control module sends a pulse width modulated 12-volt signal to
each CMP actuator solenoid to control the amount of engine oil flow to a camshaft actuator passage. There are 2 different passages for oil to flow
through, a passage for camshaft advance and a passage for camshaft retard. The camshaft actuator is attached to each camshaft and is hydraulically
operated to change the angle of each camshaft relative to crankshaft position (CKP). Engine oil pressure (EOP), viscosity, temperature, and engine oil
level can affect camshaft actuator performance. The control module calculates the optimum camshaft position through the following inputs:
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Engine speed
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Manifold absolute pressure (MAP)
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Throttle position indicated angle
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CKP
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CMP
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Engine load
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Barometric pressure (BARO)
A locking pin keeps the CMP actuators in the parked position to avoid valve train noise upon engine start-up. The parked position is 0 degrees of
camshaft actuation. The locking pin will release the actuator after the EOP is sufficient to overcome the locking pin spring pressure. The exhaust CMP
actuators also have return springs. The return springs are necessary to assist the CMP actuators to return to the parked position due to the rotational
inertia of the valve train components upon engine shutdown. The control module uses the following inputs before assuming control of the CMP actuator:
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Engine coolant temperature (ECT)
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Closed loop fuel control
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Engine oil temperature (EOT)
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EOP
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Engine oil level
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CMP actuator solenoid circuit state
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Ignition 1 signal voltage
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BARO
