Crankshaft Angle Sensor

Crankshaft angle sensor monitors engine speed and piston position. Crankshaft angle sensor is built into the distributor (G20 and M30) or into a separate sensor mounted on front of engine (Q45). Crankshaft angle sensor has a rotor plate and a wave-forming circuit. Rotor plate has 360 small (outer) slits to determine crankshaft angle (one slit for each degree of sensor rotation). Rotor plate also has 8, 6 or 4 larger (inner) slits at 45-degree (V8), 60-degree (V6) or 90-degree (4-cylinder) intervals to determine engine speed. Inner slit for No. 1 cylinder is wider than the other inner slits to allow ECU to determine TDC for No. 1 cylinder. See Figure .

When the signal rotor plate passes the space between the Light Emitting Diode (LED) and photo diode, slits in signal rotor plate alternately cut light that is sent to photo diode from LED. This causes a pulsating voltage, which is converted into an on-off pulse by wave-forming circuit, and sent to ECU. For Q45, also see SUB-CRANK ANGLE SENSOR.