Crankshaft Position Sensor: Description and Operation

PURPOSE
The engine rpm sensor produces an output pulse to the ECM 4 times per distributor rotation. The ECM uses this signal to determine engine speed and relative TDC for each cylinder.

LOCATION
The sensor is mounted inside the distributor.

CONSTRUCTION
The sensor is made up of a pick-up coil and a rotor with 4 teeth, spaced a 90° intervals. The are placed in relation to TDC at each cylinder.

OPERATION
Whenever the engine is rotating, a sine-wave signal is returned to the ECM. The pulses occurs at 90° intervals. As engine speed increases the frequency of the signal increases as well.