The anti-lock brake system (ABS) wheel speed sensor monitors the rotational speed of the wheel. A toothed ring (tone ring) rotates with the wheel and as each tooth passes through the magnetic field of the sensor, a voltage signal is sent to the ABS control module. Then the control module indicates how fast the wheel is turning by counting the number of voltage signals per second.
While the ABS wheel speed sensor are usually reliable, they can become damaged from road debris. Once they are damaged, then they will need replacing.
Most manufacturers will cover the abs wheel speed sensor under the bumper-to-bumper warranty section of the factory warranty. There are extended car warranties available that will extend coverage of wheel sensor after the factory warranty has expired. The abs wheel speed sensor may be covered under certain levels of coverage. When purchasing an extended warranty, be sure to look at the different plans to see which one includes the sensor.