Camshaft Position (CMP) Sensor
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
The camshaft position (CMP) sensor is triggered by a notched reluctor wheel built into the exhaust camshaft sprocket. The CMP sensor provides six signal pulses every camshaft revolution. Each notch, or feature of the reluctor wheel is of a different size for individual cylinder identification. This means the CMP and CKP signals are pulse width encoded to enable the PCM to constantly monitor their relationship. This relationship is used to determine camshaft actuator position and control its phasing at the correct value. The PCM also uses this signal to identify the compression stroke of each cylinder, and for sequential fuel injection. The CMP sensor is connected to the PCM by a 12-volt, low reference, and signal circuit.