Crankshaft Position Sensor

FOR MONITORING ENGINE SPEED AND CRANKSHAFT POSITION
(INDUCTIVE PULSE SENSOR - BOSCH SYSTEMS)












The engine speed (RPM) signal is provided to the Bosch engine control systems (M1.X, M3.X and M5.X) by a monolithic inductive pulse sensor. The sensor scans an incremental pulse/gear wheel that has a total of 58 teeth and a gap of two missing teeth.

Depending on the system version the pulse wheel is either mounted on the vibration damper or on the starter ring gear/flex plate at the rear of the crankshaft.

- Vibration damper: M1.x and M3.x systems.
- Rear of crankshaft: M5.x systems.

The rotation of the pulse wheel generates an A/C voltage signal in the sensor where-by each tooth of the wheel produces on pulse. The engine control module counts pulses and determines engine speed.

The gap of two missing teeth provides a reference point that the engine control module recognizes as crankshaft position.

On the M5.x systems the signal is also used as an input for misfire detection. The crankshaft position sensor is monitored as part of OBD II requirements for emission control.


FOR MONITORING ENGINE SPEED AND CRANKSHAFT POSITION
(HALL EFFECT SENSOR -SIEMENS SYSTEMS)





A hall sensor is used for the crankshaft position sensor input signal on the MS41 .x systems. 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 also contains 58 teeth with a gap of two missing teeth.

The hall sensor is supplied with 5 volts from the ECM. 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 ECM a measure of engine speed and crankshaft position.

The signal from the sensor is also used as an input for misfire detection. The crankshaft position sensor is monitored as part of OBD II requirements for emission control. The MS41.1 ECM can use the from the camshaft sensor as a replacement value (FAILSAFE) for a faulty crankshaft sensor input. However, the driveability of the vehicle is severely affected and the check engine lamp will be illuminated.