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 rings for these speed sensors spin with the hub or CV axle.

Wheel speed sensor.

A loose bearing can cause the ring to wobble and damage the wheel speed sensor's tip. This damage results in an ABS warning light. Scanning the system for a fault code points to the faulty circuit. Sometimes mud or road debris gets into the gap or between the tone sprockets creating a problem with the signal.

Wheel bearing inspection. Rock the tire back and forth.

Inspect the wheel bearings by grasping the tire at the top and bottom and rocking it back and forth. Excessive play indicates a loose wheel bearing. Faulty wheel bearings make a growling or whining sound that increases with vehicle speed and while turning.