Front
FRONT WHEEL SPEED SENSORDESCRIPTION
This system uses two-wire wheel speed sensors known as active wheel speed sensors. One Wheel Speed Sensor (WSS) and one tone wheel is located at each front and rear wheel. Each front wheel speed sensor is attached to a boss in the steering knuckle. The front tone wheel is part of the outboard constant velocity joint.
OPERATION
The CAB sends 12 volts to power an Integrated Circuit (IC) in the sensor. The IC supplies a constant 7 mA power supply to the CAB. The relationship of the tooth on the tone wheel to the permanent magnet in the sensor, signals the IC to enable a second 7 mA power supply. The output of the sensor, sent to the CAB, is a DC voltage signal with changing voltage and current levels. The ground for the IC and the current sense circuit is provided by the CAB.
When a valley of the tone wheel is aligned with the sensor, the voltage signal is approximately 0.8 volts and a constant 7 mA current is sent to the CAB. As the tone wheel rotates, the tooth shifts the magnetic field and the IC enables a second 7 mA current source. The CAB senses a voltage signal of approximately 1.6 volts and 14 mA. The CAB measures the amperage of the digital signal for each wheel. The resulting signal is interpreted by the ABS the wheel speed.