Camshaft Position (CMP) Sensor

CMP sensor monitors engine speed and piston position. CMP sensor is built into distributor on G20. CMP sensor has a rotor plate and a wave-forming circuit. Rotor plate has 360 small (outer) slits to determine camshaft position (one slit for each degree of sensor rotation). Rotor plate also has 4 (4-cylinder) large inner slits at 90-degree intervals to determine engine speed. Inner slit for cylinder No. 1 is wider than the other inner slits to allow ECM to determine TDC for cylinder No. 1.

The signal rotor plate passes between a Light Emitting Diode (LED) and photo diode when 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 ECM.