Crankshaft Position Sensor: Description and Operation

DESCRIPTION
The crankshaft position sensor is located opposite the teeth on the flywheel and uses a non contact method to record the position of the crankshaft. The leading edges of each tooth on the flywheel generate a positive signal in the position sensor, while the trailing edges generate a negative signal. When the crankshaft is rotating, an alternating voltage is produced as a result.

The period of the signal is the time required by the crankshaft to turn through the gap between two flywheel teeth. The clearance between the crankshaft position sensor and the teeth of the flywheel is fixed by the installation.

Two teeth on the flywheel are missing. The resulting signal gap is used by the ECM to detect the TDC position of cylinder number one.

OPERATION
The clearance between the crankshaft position sensor and the flywheel are fixed by the installation position. Two teeth on the flywheel are missing. The resulting gap is used by the ECM to detect DTC of cylinder number one. The crankshaft position is calculated to an accuracy of a fraction of a degree so that the start and end of injection can occur at exactly the right moment. The engine speed signal is also processed by the ECM from the crankshaft sensor. This signal is then transferred to other control modules over the CAN bus.

If the crankshaft position sensor fails, the signal that provides reference rotation is missing. Injection may occur at the wrong time and damage the engine. In this case, the ECM will stop triggering the injectors, the engine would cut out, the engine warning light would illuminate and the engine will not restart.