Crankshaft Angle Sensor

The crankshaft angle sensor monitors engine speed and piston position. The crankshaft angle sensor, which is built into the distributor, has a rotor plate and a wave-forming circuit. The rotor plate has 360 small slits, each slit determines crankshaft angle (one slit for each degree of rotation) and 4 or 6 large slits at 90 or 60 degrees each, to determine engine speed (4 slits at 90 degrees on 4 cyl., 6 slits at 60 degrees on 6 cyl.).

When the signal rotor plate passes the space between the Light Emitting Diode (LED) and photo diode, the slit in the signal rotor plate alternately cuts the light which is sent to the photo diode from the LED. This causes a pulsating voltage, which is converted into an on-off pulse by the wave-forming circuit and sent to the ECU.