Crankshaft Position Sensor: Description and Operation

The crank angle sensor monitors engine speed and piston position and sends corresponding signals to the electronic control unit to control various system functions. The sensor has a rotor plate and wave forming circuit. The rotor plate has 360 slits for 1° engine speed signal and one slit for each cylinder for crank angle signal. Light Emitting Diodes (LEDs) and photo diodes are integral with the wave forming circuit.
When the rotor plate passes the space between the LEDs and photo diodes, the slits in the plate cuts the light sent to the photo diode from the LEDs. This action creates a voltage which is converted to an on-off pulse by the wave forming circuit and transmitted to the control unit.