C 2500 Truck 2WD V8-5.7L VIN R (1997)
Wheel Speed Sensor: Description and Operation
The front Wheel Speed Sensor (WSS) is a magnetic coil/pickup that mounts to the front steering knuckle. It produces an AC voltage signal to tell the
Electronic Brake Control Module (EBCM) how fast the wheel is turning. The speed of the wheel is directly proportional to the frequency of pulses the
sensor produces. The WSSs connect to the EBCM through the 5-pin connector. On 2WD models, the WSSs mount to the dust shields (except C
3500HD). On 4WD models, the WSSs are integrated into the front wheel bearing along with the tone wheels.
Front Wheel Speed Sensor Tone Wheels
The front Wheel Speed Sensors (WSS) use tone wheels to produce an AC voltage signal. Tone wheels are metal rings with teeth on the outside
diameter. The AC voltage is produced as the teeth come into and leave alignment with the sensor pole piece. The tone wheels are attached to the rotor
on 2WD models and are integral with the wheel bearing on 4WD models. Any imperfectins in the tone wheels, such as a broken or missing tooth, can
cause an inaccurate wheel speed reading on the affected wheel.
Wheel Speed Sensor Calibration
The Four Wheel Antilock (4WAL) Electronic Brake Control Module (EBCM) is capable of accepting wheel speed signals from several different size
tire and wheel combinations. All vehicles are preprogrammed from the factory with the proper front tire size calibration. Whenever the 4WAL EBCM
is replaced, it is necessary to reset the tire size calibration. Once programmed, this calibration will remain even if the battery is disconnected or the
EBCM is removed from the vehicle.
