Functional description

The increment gear has 58 teeth as well as a reference gap of 2 teeth.

The reference gap enables detection of the upper dead center of the 1st cylinder. By monitoring the individual teeth, the Hall effect sensor delivers a certain number of signal jumps to the engine control system.

Fig 1: Identifying Crankshaft Sensor And Plug Connection

Courtesy of BMW OF NORTH AMERICA, INC.

The engine control unit uses the scanned tooth flanks to calculate the duration and length of a crankshaft revolution.

The time that the increment wheel requires to rotate past the hall effect sensor is referred to as the crankshaft revolution per time.

For starting the engine, the engine control unit checks the following preconditions:

• error-free signal from the crankshaft sensor and camshaft sensor
• both signals must be detected in a specific chronological sequence

This process is referred to as synchronization and is only performed when the engine is started. It is only the synchronization process that enables the engine control unit to activate fuel injection correctly. The engine will not start without synchronization. If the crankshaft sensor signals fails (with the 1st crankshaft revolution) or an invalid synchronization is detected for the engine start, the diagnosis starts immediately. The camshaft sensor signals are read here. If 12 flanks on the camshaft are read and the fault is still there, a fault is stored.

As soon as no crankshaft sensor signals are received or there is no valid synchronization with the engine running, debouncing starts.