Wheel Speed Sensor Encoders
WARNING: This page is about a different car, the 2016 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.
The wheel speed sensor encoders are several magnets arranged in a circle around one side of the wheel bearing in alternating poles. As the bearing rotates the wheel speed sensor is exposed to alternating north-south magnetic fields. The encoder is part of the wheel bearing and is serviced with the bearing.