Wheel speed sensors are often called ABS sensors. You'll find them mounted on the axles of all ABS equipped vehicles on your wheel hubs, near the brake rotors. The ABS sensor is a vital part of the braking system. Without a working ABS wheel speed sensor, the ABS system will fail to work properly. Resulting in a ABS Light on your Dash and loss of your Antilock Brake System. Fit 00-03 BMW X5