Camshaft Actuator System

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

The Camshaft Position (CMP) actuator system enables the Powertrain Control Module (PCM) to change camshaft timing while the engine is running. See Fig 1 . The CMP actuator assembly varies camshaft position in response to directional changes in oil pressure. The CMP actuator solenoid valve controls the oil pressure that is applied to advance or retard the camshaft. Modifying camshaft timing under changing engine demand provides better balance between the following performance concerns:

Engine power output.
Fuel economy.
Lower tailpipe emissions.

The CMP actuator solenoid valve is controlled by the PCM. The Crankshaft Position (CKP) sensor and the CMP sensor are used to monitor changes in camshaft position. The PCM uses information from the following sensors in order to calculate the desired camshaft position:

Engine Coolant Temperature (ECT) sensor.
Mass Air Flow (MAF) sensor.
Throttle Position (TP) sensor.
Vehicle Speed Sensor (VSS).

Fig 1: Identifying Camshaft Actuator System Components

Courtesy of GENERAL MOTORS CORP.