Crankshaft Position Sensor: Description and Operation

Engine Speed Sensor:

PURPOSE
The crankshaft position sensor generates an input signal for the ECM regarding crankshaft position and engine speed.

LOCATION
Front of engine, forward of bell-housing.

CONSTRUCTION
The sensor consists of a permanent magnet, a pole tip which concentrates a magnetic field at the end of the device and a coil. The magnet creates a magnetic field which varies in strength as the tooth wheel passes the tip.

OPERATION
Voltage is induced in the sensor as each tooth on the gearwheel passes the tip. The gearwheel uses a two-tooth gap to indicate crankshaft position.

This voltage signal supplies the ECM with a unique electrical picture from which it can determine both crankshaft position and engine speed.

SIGNAL
The frequency of the signal is used to determine the engine speed.

The position of the "tooth gap" in conjunction with the Camshaft Position Sensor signal indicates ignition TDC for #1 cylinder.

SELF-DIAGNOSIS
The ECM recognizes a missing signal from the sensor within five seconds of cranking. If the position sensor and Camshaft Position Sensor signals are incorrect, a fault code is registered. The vehicle will not start.