Anti-Lock Brake System (ABS) Module

The ABS module is an on-board diagnostic, non-repairable unit consisting of the microprocessors and the necessary circuitry for their operation and is mounted to the HCU. The ABS module communicates with the diagnostic tool over the international standards organization (ISO) communication bus, circuit 70 (LB/WH). The ABS module monitors system operation during normal driving as well as during anti-lock braking.

ABS module operation is as follows:

• Under normal driving conditions, the microprocessor produces short test pulses to the solenoid valves that check the electrical system without any mechanical reaction.
• Impending wheel lock conditions trigger signals from the ABS module that open and close the appropriate solenoid valves. This results in moderate pulsations in the brake pedal.
• The ABS module used in 4x4 application includes a G-sensor. It detects vehicle movements during a brake lockup event that is transferred to other wheels through the powertrain.

During normal braking, the brake pedal feel will be identical to a standard brake system.

Most faults that occur in the anti-lock brake system will be stored as a diagnostic trouble code (DTC) in the keep-alive memory of the ABS module. The DTCs can be retrieved by following the on-board diagnostic procedures.