Wheel Speed Sensors
The sensors used on the Discovery 2 are incorporated into the wheel bearing on both the front and rear hubs. This is a sealed unit and has no replaceable parts. The wires from the wheel speed sensors is a twisted pair. The wire twists provide improved resistance to electrical interference. The signal produced from the wheel speed senor is an AC sine wave. The signal is generated in the inductive sensor by a 60 tooth reluctor ring. This reluctor ring is machined into the wheel bearing inner race. The frequency of the sine wave signal supplies the ABS ECU with the information it needs to determine the speed of the individual wheels. Each wheel speed sensor has a resistance of 950-1100 ohms.

Wheel Speed Sensor Failures
Wheel speed sensor faults are a very common occurance. Where as the actual failure of a wheel speed sensor is not a common event. The most common Logged ABS wheel sensor faults are caused by worn brake pads. A worn brake pad or even some new non-Land Rover Brake pads can set up a resonance vibration in the wheel hub. This vibration can interfear with the ABS sensor signal. When the ABS sensor signal is interrupted an ABS wheel speed sensor fault can be logged. Best advice is to clear the fault and take the vehicle for a test drive. Other causes of the wheel speed sensor fault can be caused by a bad wheel hub. Recomended approach is to inspect the wheel hub and make sure the hub does not have excessive play. A bad wheel hub can cause the ABS reluctor ring to deviate from the sensor range.