Camshaft Position Sensor
A 3-wire Camshaft Position (CMP) sensor is located at top of timing cover, behind water pump. See Fig 1 . The CMP sensor signal is a digital ON/OFF pulse, output once per revolution of the camshaft. The CMP sensor does not directly affect the operation of the ignition system. The CMP sensor information is used by the Powertrain Control Module (PCM) to determine the position of the valve train relative to the crankshaft position. By monitoring the CMP and Crankshaft Position (CKP) signals the PCM can accurately time the operation of the fuel injectors. The PCM supplies the sensor with a 12-volt reference, low reference, and signal circuit.
During cranking, the Ignition Control Module (ICM) monitors the 7X CKP sensor signal. Once the engine starts the ICM determines spark synchronization, by the CMP sensor pulses. The PCM constantly monitors the number of pulses on the CMP signal circuit and compares the number of CMP pulses to the number of 24X reference pulses and the number of 3X reference pulses being received.