Crankshaft Position Sensor: Description and Operation

The crank angle sensor monitors engine and piston position sending signals to the E.C.U. controlling fuel injection, ignition timing and other related functions.
The sensor has a rotor plate and a wave forming circuit. On G20 models, the rotor plate has 360 slits for 1° signal and 4 slits for 180° signal. On M30 models, the rotor plate has 360 slits for 1° signal and 6 slits for 120° signal. Light emitting diodes (L.E.D.) and photo diodes are integral to the wave forming circuit.
As the rotor plate passes between the L.E.D. and photo diode, slits in the rotor plate continually cuts the light being transmitted to photo diode from the L.E.D., generating rough shaped pulses which are converted into on-off pulses by the wave forming circuit, which are sent to the E.C.U.