Wheel speed sensor, function - GF42.45-P-4550-02S

WARNING: This page is about a different car, the 2009 Mercedes-Benz E550 and 2008 Mercedes-Benz E550. However, it is still accessible from the selected car via links, so may be relevant.

Models 211, 230, 240

The diagram shows the current path through the active wheel speed sensor during an acceleration phase

Fig 1: View Of Current Path Of Active Wheel Speed Sensor During Acceleration Phase

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Function of the active wheel speed sensor

The strength and direction of an external magnetic field causes a change in the internal resistance inside the sensor. Electronic processing circuitry in the sensor generates a square-wave signal characterized by a constant amplitude level in which the frequency varies to reflect fluctuations in the rotation rate. The system recognizes the vehicle's direction of travel based on the signal patterns for left and right side wheel rotation. This signal is received by the relevant dynamic handling control system and transmitted over the CAN.

The sensor can also detect unsatisfactory installation positions and relay this information to the SBC control unit.

The external magnetic field is generated by a multipole reluctor ring.

This consists of an elastomer plastic containing metallic particles. These are aligned by a special magnetization method so as to produce various magnets whose polarity at the circumference alternates from north to south.