An antilock brake wheel speed sensor measures the speed of each wheel by counting the number of revolutions each wheel makes while braking to be sure the wheel isn't locking up. If a wheel locks up, the antilock brake control module can apply or release brake fluid pressure to each wheel, releasing the wheel from its locked state.
To replace the ABS wheel speed sensor, the wheel is removed. The sensor is then found near the wheel bearing hub. The sensor is electrically disconnected, removed, and replaced with the new component. In some vehicles the sensor is incorporated with the hub assembly and the entire hub assembly must be replaced.
The wheel speed sensors are reliable but may be damaged if they come into contact with road debris.