A warning light can appear while the vehicle still seems completely normal from behind the wheel. The brake pedal feels familiar, the engine runs as expected, and nothing obvious changes during an ordinary trip around town. Then an ABS light, traction-control warning, or stability-control message suddenly appears on the dashboard. Those warnings can trace back to information coming from one of the wheels. Modern vehicles constantly compare wheel speeds while you drive, and several safety systems depend on that information. When one signal disappears or becomes unreliable, the effects can extend beyond the sensor at that wheel. What an ABS Wheel Speed Sensor Measures Each wheel speed sensor monitors how quickly its wheel is rotating and sends that information to the ABS control unit. Depending on the design, the sensor reads a toothed reluctor ring or a magnetic encoder incorporated into the wheel bearing or hub assembly. HELLA notes that wheel speed information is used by ABS, tract ... read more