The controlling element of ABS is the electronic brake control module. Inputs to the system include four wheel speed sensors, brake switch, ignition switch, and unswitched battery power. Outputs include four air modulators and the ABS indicator lamp. The EBCM monitors the speed of each wheel. If any wheel begins to approach lock-up, the EBCM controls the air modulators to reduce brake pressure to the wheel approaching lock-up. Once the wheel regains traction, brake pressure is increased until the wheel again begins to approach lock-up. This cycle repeats until either the vehicle comes to a stop, the brake is released, or no wheels approach lock-up. Additionally, the EBCM monitors itself, each input and output for proper operation. If any system malfunction is detected, the EBCM will illuminate a light emitting diode(s) located in a window on the side of the EBCM housing. These diagnostic LED's are referred to as the diagnostic status lamps.

Wheel speed information is provided to the EBCM via a wiring harness from individual wheel speed sensors located at the wheels. Working in conjunction with a tone ring, wheel speed sensors provide information to the EBCM in the form of an AC voltage signal which varies in voltage and frequency as the speed of the wheel increases or decreases. The wheel speed sensor is installed in a mounting block on the axle housing. A spring loaded retaining clip is used to secure the wheel speed sensor into the mounting bore. This spring retainer is designed in a way that allows the wheel speed sensor to slide back and forth under force, but will retain its position when force is removed. This allows the wheel speed sensor to self adjust after it is installed in the mounting bore and allows for an air gap between the wheel speed sensor and tone ring.

Each wheel speed sensor (WSS) uses a tone wheel in order to produce an AC voltage signal. Tone wheels are metal rings with teeth on the outside diameter. The AC voltage is produced as the teeth pass through the magnetic field of the WSS pole piece. The tone wheels are attached to the rotor or the drum. Any imperfections in the tone rings, such as a broken tooth or a missing tooth, can cause an inaccurate wheel speed signal.

The EBCM accepts wheel speed signals from several different sizes of tire and wheel combinations. All vehicles are preprogrammed from the factory with the proper tire size calibration. Whenever tires of a different size are installed on the vehicle, the EBCM will automatically recalibrate itself to compensate.