Anti-Lock Brake Control Module
The anti-lock brake control module is a non-repairable, on-board diagnostic unit consisting of one microprocessor and the necessary circuitry for its operation. The two primary functions of the anti-lock brake control module are to control the HCU during ABS operation and to monitor the system during normal driving, as well as during anti-lock braking.

Under normal braking conditions, the microprocessor produces short test pulses to check the electrical system without any mechanical reaction. The anti-lock brake control module continuously monitors the speed of each wheel to determine if any wheel is beginning to lock. When a wheel locking tendency is detected, the anti-lock brake control module signals the appropriate isolation valve and/or dump valve in the HCU to open or close as well as the pump motor to turn on and return brake fluid back to the foundation braking system.

Most faults that occur in the ABS will be stored as a Diagnostic Trouble Code (DTC) in the anti-lock brake control module. Once a DTC is stored, it will be retained by the anti-lock brake control module even with the key in the OFF position. DTCs can be retrieved by following the on-board diagnostics procedures.