Crankshaft sensor

The crankshaft sensor records the position of the crankshaft with the aid of an increment gear screwed to the crankshaft. The DME uses this to calculate the engine speed. The crankshaft sensor is necessary for the fully sequential injection system (fuel injection takes place individually for each cylinder at the specific point of ignition).

The signal from the crankshaft sensor means that the DME also evaluates the crankshaft acceleration. The crankshaft acceleration provides an indication of the combustion quality of individual cylinders.

Fig 1: Identifying Crankshaft Sensor And Plug Connection

Courtesy of BMW OF NORTH AMERICA, INC.

Power is supplied to the sensor by the DME with 5 Volts and ground. The sensor delivers a digital signal via the signal cable to the DME. As of approx. 20 RPM, a signal that can be evaluated is output. The tooth gap is detected by the control module in that the measured distance between the tooth gaps is more than double the size of the previous and succeeding gaps. The tooth gap itself is assigned to a defined crankshaft position of cylinder 1. At this point in time, the DME synchronizes the crankshaft position. With each subsequent low signal, it counts the crankshaft position on by 6°.