Wheel Speed Sensors
| Item Number | Description |
|---|---|
| 1 | Knuckle assembly |
| 2 | Sensor ring |
| 3 | Halfshaft |
| 4 | Wheel speed sensor |
| 5 | Screw |
An active wheel speed sensor is installed in each wheel hub to provide the anti-lock brake system (ABS) module with a rotational speed signal from each road wheel. The head of each wheel speed sensor is positioned close to a 48 tooth sensor ring on the outer diameter of the constant velocity joint of the halfshaft. A flying lead connects each sensor to the vehicle wiring.
The wheel speed sensors each have a power supply connection and a signal connection with the anti-lock brake system (ABS) module. When the ignition switch is in position II, the anti-lock brake system (ABS) module supplies power to the wheel speed sensors and monitors the return signals. Any rotation of the halfshafts induces current fluctuations in the return signals which are converted into individual wheel speeds and the overall vehicle speed by the anti-lock brake system (ABS) module.
The anti-lock brake system (ABS) module outputs the individual wheel speeds and the vehicle speed on the high speed controller area network (CAN) bus for use by other systems. The quality of the vehicle speed signal is also broadcast on the high speed controller area network (CAN) bus. If all wheel speed signals are available to calculate vehicle speed from, the quality of the vehicle speed signal is set to 'data calculated within specified accuracy'. If one or more wheel speed sensors is faulty, the quality of the vehicle speed signal is set to 'accuracy outside specification'.
The anti-lock brake system (ABS) module monitors the wheel speed sensor circuits for faults. If a fault is detected the anti-lock brake system (ABS) module stores a related fault code and illuminates the appropriate warning indicators, depending on the system functions affected (DSC/ETC, anti-lock brake system (ABS), emergency brake assist (EBA)/electronic brake force distribution (EBD), HDC). Also a warning chime sounds and a related message is shown in the message center. Refer to INSTRUMENT CLUSTER .
Since the wheel speed sensors are active devices, a return signal is available when the road wheels are not turning, which enables the anti-lock brake system (ABS) module to check the sensors while the vehicle is stationary. In addition, the direction of travel of each wheel can be sensed. This information is broadcast on the high sped controller area network (CAN) bus for use by other systems.