Camshaft Position (CMP) Sensor (Except Maxima)
CMP sensor monitors engine speed and piston position. CMP sensor, which is built into distributor (4-cylinder), or mounted to front cover of engine facing camshaft (V6), has a rotor plate and a wave-forming circuit. Rotor plate has 360 small outer slits (one degree apart) to determine engine speed and 4 (4-cylinder) or 6 (V6) larger inner signal slits, 90 (4-cylinder) or 60 (V6) degrees apart, to determine camshaft position. See Fig 1. The signal slit for cylinder No. 1 is the largest inner signal slit to allow PCM to determine TDC for cylinder No. 1.
When signal rotor plate passes space between Light Emitting Diode (LED) and photo diode, slits in signal rotor plate alternately cuts light from LED to photo diode. This causes a pulsating voltage, which is converted into an on-off pulse by wave-forming circuit and sent to PCM. PCM uses this signal to control fuel injection, ignition timing and other functions.