Crankshaft Position (CKP) Sensor

The CKP sensor monitors engine speed and piston position. The CKP sensor, which is built into the distributor, has a rotor plate and a wave-forming circuit. The rotor plate has 360 small outer slits (one degree apart) to determine CKP and 4 (4-cylinder) or 6 (V6) larger inner signal slits, 90 (4-cylinder) or 60 (V6) degrees apart, to determine engine speed. See Figure . The signal slit for cylinder No. 1 is the largest inner signal slit to allow ECM to determine TDC for cylinder No. 1.

When the signal rotor plate passes the space between the Light Emitting Diode (LED) and photo diode, the slits in the signal rotor plate alternately cut the light from LED to the photo diode. This causes a pulsating voltage, which is converted into an on-off pulse by the wave-forming circuit and sent to the ECM. ECM uses this signal to control fuel injection, ignition timing and other functions.