Steering Angle Sensor (LEW)

The Steering Angle Sensor is mounted towards the lower end of the steering column, above the flexible coupling. The LEW consists of a potentiometer and a built in microprocessor. The potentiometer has two pickups offset at 900 to one another. The raw potentiometer signal is processed and converted into a digital signal that is transmitted over the CAN bus to the DSC control unit.

Fig 1: Steering Angle Sensor Signal Graph

Courtesy of BMW OF NORTH AMERICA, INC.

The sensor requires initialization in-order to create a zero point default. Once initialized, the LEW sends an ID number to the DSC control unit. The ID provides confirmation that the LEW is properly initialized.

The total steering wheel angle is determined by combining the CAN telegram signal, the stored zero point default and the actual number of turns to the wheel. In order to prevent the LEW from loosing count, KL 30 is provided to the sensor and it continues to record even after the ignition has been switched off.

The DSC calculates the drivers desired rate of turn from the steering angle signal.

Fig 2: Identifying Steering Angle Sensor

Courtesy of BMW OF NORTH AMERICA, INC.

NOTE: Refer to the Workshop Hints for instructions on coding and initializing the sensor.