Final answer:
An ABS wheel speed sensor provides an AC pulse signal resembling a sinewave, which is used by the vehicle's ECU to monitor and adjust wheel speed during braking.
Step-by-step explanation:
The ABS wheel speed sensor typically provides an AC pulse, which is produced by the sensor as the wheel rotates. This signal is a form of a varying voltage that resembles a sinewave. The ABS sensor uses a magnetic field in conjunction with a toothed wheel attached to the hub of the wheel. As the wheel turns, the teeth pass through the magnetic field of the sensor, generating an alternating current (AC) voltage that matches the speed of the wheel's rotation. This signal is then interpreted by the vehicle's electronic control unit (ECU) to determine the wheel's speed and, if necessary, to adjust the brake pressure during an ABS event to prevent wheel lock-up.