Where is ABS sensor?

The ABS sensor is located in each wheel hub/rotor on a four channel ABS system. Older configurations of ABS had the sensors located outside the wheel hub in parts such as the steering knuckle and differential housing. The ABS sensor is coupled with a ring gear, mounted on components such as the brake rotor and brake drum. The ABS sensors in newer systems are fitted in the wheel hub assembly itself. Vehicles may have as few as one or up to four ABS sensors depending on the type of braking system.