The ABS control unit uses information from the wheel speed sensors for ABS control and TC.
The pulse ring sits on the wheel hub. When the wheel rotates, the wheel speed sensor detects the wheel's rotation. The signals are sent on the ABS control unit, which continually receives information on wheel rotational speed. There must not be too large of an air gap between the pulse ring and the wheel speed sensor; otherwise the signal will fail to generate or will be incorrect.