ABS Wheel Speed Sensor Inspection

ABS tone wheel on a hub with wheel bearings.

ABS equipped vehicles contain wheel speed sensors mounted on the suspension and steering knuckles. The tone ring for these speed sensors is incorporated into the hub or CV axle. It’s inner bearing is fastened to an axle that rotates at wheel speed. Inspect the wheel bearings by grasping the tire at the top and bottom and rock the it back and forth. Excessive play indicates a loose wheel bearing.

Wheel bearing inspection. Rock the tire back and forth.

Faulty wheel bearings make a growling or whining sound that increases with vehicle speed or while turning. The loose bearing can cause the ring to wobble and damage the wheel speed sensor’s tip. This results in an ABS warning light. Scanning the system for a code will quickly point to the faulty circuit. Sometimes mud or road debris gets into the gap or between the tone sprockets creating a problem with the signal.