Skip to Content

What’s a Wheel Speed Sensor?

A wheel speed sensor (WSS) is a small sensor used to detect precisely how fast a road wheel is turning. The wheel speed sensor won’t work without a reluctor ring, also known as a tone ring or sensor ring. The reluctor turns with the wheel, and the fixed wheel speed sensor is positioned just mm from the reluctor; the distance is important and is known as the air gap.

As the reluctor spins with the wheel, the sensor registers its movement and passes the signal to the ABS unit for processing.

Wheel speed sensor information is critical for the operation of the ABS, Traction control, Stability Control, ECU, Cruise control, and many other seemingly unconnected systems such as steering wipers, even infotainment systems rely on WSS info.

Where is Wheel Speed Sensor Located?

Wheel speed sensor

A wheel speed sensor is located at each wheel of the vehicle.

Typically the sensor is mounted in a void in the suspension knuckle close to the wheel bearing where the reluctor ring is positioned and more commonly the reluctor/tone ring is wheel bearing integrated.


Common Wheel Speed Sensor Problems

Wheel speed sensors live in a difficult environment, wind, rain, road grime, potential impact from debris, snow, Ice, road salt, heat – it gets it all.

You won’t be surprised to know they do fail somewhat regularly. That said, often, it’s not the sensor itself but a relatively simple root cause.

Issues include:

Whel Speed Sensor
  • Loose wiring
  • Corroded wire
  • Damaged terminal connector
  • Base plate corrosion (causing an incorrect sensor to reluctor air gap)

Other helpful posts: