An anti-lock braking system includes a sensor apparatus that includes a sensor body. In a first position, the sensor body is positioned such that a desired gap is maintained between the sensor body and a reference point located on a tone ring, which is rotatably coupled to a corresponding wheel hub. In the first position, a spring-loaded plunger holds the sensor body in place. When the sensor body is moved to a second position, a plunger pin is displaced within the plunger, putting tension on an internal spring. The tension in the spring returns the sensor body to the first position.