Sensor-Front Wheel Speed: Description

The antilock brake system uses two-wire wheel speed sensors, known as active wheel speed sensors. The sensors use an electronic principle known as magnetoresistive to help increase performance and durability. The sensors convert wheel speed into a small digital signal. A wheel speed sensor (WSS) is used at each wheel. The gear (tooth) type tone wheel serves as the trigger mechanism for each sensor. At each wheel of the vehicle there is one wheel speed sensor and one tone wheel.

Fig 1: Wheel Speed Sensor & Tone Wheel Location (Heat Shield Removed)

Courtesy of DAIMLERCHRYSLER CORP.

A front wheel speed sensor (1) is attached to a mounting boss on each front knuckle. There is a heat shield mounted between each sensor and the knuckle. The tone wheel (2) is an integral part of the outboard constant velocity joint located in the front axle half shaft.

WSS air gaps are not adjustable. For the WSS air gap specification, (Refer to BRAKES - ABS - SPECIFICATIONS)  . Each WSS is serviced individually. The tone wheels are serviced as part of the axle half shaft.