Camshaft Position Sensor: Description and Operation

The camshaft position sensor (CMPS) is a basic component of the ECM. It monitors engine speed and piston position. It sends signals to the ECM to control fuel injection, ignition timing and other functions.

The camshaft position sensor has a rotor plate and a wave-forming circuit. The rotor plate has 360 slits for 1° signal and 8 slits for 90° signal. Light Emitting Diodes (LED) and photo diodes are built into the wave-forming circuit.

When the rotor plate passes between the LED and the photo diode, the following happens:

Slits in the rotor plate continually cut the transmitted light to the photo diode from the LED. This generates rough-shaped pulses converted into on-off pulses by the wave forming circuit sent to the ECM.