The engine speed sensor is located in the rear end cover of the crankcase. The DDE control unit supplies the sensor with ground (M_KWG) and a supply voltage of 5 V (U_KWG).
On the crankshaft there is a sensor wheel which has 58 small permanent magnets around its perimeter. As the crankshaft rotates, those magnets move past the engine speed sensor, thereby producing the speed sensor signal.
In the point of the sensor, there are four resistors connected in a bridge circuit. When the permanent magnets move past the sensor, the direction of the magnetic field acting on the resistors. That change of direction generates a sine-wave fluctuation in resistor impedance.
The sensor has an integral evaluation circuit which converts the impedance fluctuation into a square-wave voltage signal. The DDE control unit analyses that voltage signal in order to calculate the engine speed.
The rpm sensor signal is used as a measurement variable for:
The following faults are monitored:
Consequence: