Wheel speed sensors (Discovery 3)

Item name	Spare part number	Description
1	-	Wheel fist assembly
2	-	Sensor Ring
3	-	half shaft
4	-	Wheel speed sensor
5	-	Screw

An active wheel speed sensor is installed on the hub of each wheel, which transmits to the ABS module (anti-lock braking system) speed signal for each impeller. The head of each sensor is adjacent to a 48-tooth sensor ring on the outside diameter of the CV joint. Each sensor is connected to the vehicle wiring by flying leads.

Each of the wheel speed sensors is connected to the ABS module (anti-lock braking system) power circuit and signal circuit. When the ignition key is in position II, the ABS module (anti-lock braking system) supplies power to the wheel speed sensors and monitors their signals. When the half shaft rotates, the current strength of the sensor signal changes; based on these changes by the ABS module (anti-lock braking system) wheel speed and overall vehicle speed are calculated.

ABS module (anti-lock braking system) transmits information about the speed of individual wheels and the speed of the vehicle via a high-speed CAN bus (controller network) for use by other systems. Also via high-speed CAN bus (controller network) the quality factor of the vehicle speed signal is transmitted. If all wheel speed signals are available for the vehicle speed calculation, the vehicle speed signal quality factor is "data are calculated with specified accuracy". If one or more wheel speed sensors fail, a quality factor is used "accuracy does not match the specified".

ABS module (anti-lock braking system) monitors wheel speed sensor circuits for faults. When a malfunction is detected, the ABS module (anti-lock braking system) saves the appropriate fault code and turns on the appropriate warning lamps, depending on the systems that are malfunctioning (DSC/ETC, ABS, EBA/EBD, HDC). A warning chime sounds and, on vehicles with a high-level instrument cluster, the message center display shows a warning message. For more information, please refer to the Information and Message Center (413-08)

Since the wheel speed sensors are active devices, the signal from them is received even when the wheels are not rotating, which allows the ABS module to (anti-lock braking system) check the sensors on a stationary vehicle. In addition, the direction of rotation of each wheel is determined. This information is transmitted over the high-speed CAN bus (controller network) for use by other systems.