Camshaft Position Sensor: Description and Operation

CAMSHAFT POSITION (CMP) SENSOR
The camshaft position (CMP) sensor is a Hall-Effect type sensor. The CMP signal is a digital ON/OFF pulse, which outputs 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 ECM to determine the position of the valve train relative to the crankshaft position. By monitoring the CMP and CKP signals, the ECM can accurately trigger the fuel injectors. This allows the ECM to calculate true sequential fuel injection mode of operation. If the CMP signal is lost while the engine is running, the fuel injection system will shift to a calculated sequential fuel injection mode based on the last fuel injection pulse, and the engine will continue to run. The ECM supplies the sensor with a 12-volt reference, a low reference, and a signal circuit.

CAMSHAFT RELUCTOR WHEEL
The camshaft reluctor wheel is bolted to the front of the camshaft. The wheel is a smooth track, half of which is of a lower profile than the other half. This track is read in a radial or axial fashion respectively. This allows the CMP sensor to supply a signal as soon as the key is turned ON, since the CMP sensor reads the track profile, instead of a notch.