Crankshaft Position Sensor: Description and Operation

A Hall sensor is used for the crankshaft position sensor input signal on the MS41.1 system. The RPM/reference sensor is mounted on the left side at the rear of the cylinder block. The trigger wheel is now mounted inside the crankcase, on the crankshaft, at the rear main bearing support. The trigger wheel still contains 58 teeth with a gap of two missing teeth.

The hall sensor is supplied with 5 volts from the control module. A digital square wave signal is produced by the sensor as the teeth of the trigger wheel pass by. This type of signal can be directly processed by the control module as a measure of engine speed and crankshaft position.

The signal from the sensor is also used as an input for misfire detection. As part of the 1996 OBD II emission requirements, the engine control module must be able to detect a misfiring cylinder from either electrical or mechanical faults.

If the OBD II fault monitoring criteria for misfire are satisfied, the Check Engine Lamp will illuminate.

The crankshaft position sensor is monitored as part of the OBD II requirements for emission control. The MS41.1 Control Module can use the signal from the camshaft sensor as a replacement value (FAIL-SAFE) for a faulty crankshaft sensor input. However, the driveability of the vehicle is severely affected. The Check Engine Lamp will be illuminated for a faulty sensor input.