Wheel Speed Sensor

On vehicles not equipped with active park assist, all 4 wheel speed sensors are active (magneto resistive) sensors that operate on the Hall-effect principle to generate a square wave signal that is proportional to the rotational speed of the wheel. Because these are active sensors, receiving voltage from the Anti-Lock Brake System (ABS) module and then sending a varying voltage back to the Anti-Lock Brake System (ABS) module, they are able to detect much lower rotational speeds than passive (magnetic inductive) sensors. Each wheel speed sensor is connected to the Anti-Lock Brake System (ABS) module by 2 circuits. One circuit provides voltage for sensor operation and the other circuit provides sensor input to the Anti-Lock Brake System (ABS) module.

On vehicles equipped with active park assist, both rear wheel speed sensors are active, bi-directional sensors. Each of the 2 sensors contain 2 sensing elements mounted side-by-side. Because the 2 sensing elements are mounted next to each other the 2 voltage signals are slightly out of phase, which causes one element to generate a voltage signal before the other element. This allows the Anti-Lock Brake System (ABS) module to not only determine wheel speed, but also wheel direction for active park assist.