Module, Anti-Lock Brake System: Operation: Operation: Notes

The primary functions of the Anti-lock Brake System (ABS) Module are to:

• monitor the brake system for proper operation.
• detect wheel locking or wheel slipping tendencies by monitoring the speed of all four wheels of the vehicle.
• control fluid modulation to the wheel brakes while the system is in an ABS event mode.
• store diagnostic information.
• provide communication to the scan tool while in diagnostic mode.

The ABS Module constantly monitors the brake system for proper operation. If the ABS detects a fault, it will turn on the amber ABS warning indicator lamp and disable the anti-lock braking system. The normal base braking system will remain operational.

The ABS continuously monitors the speed of each wheel through the signals generated by the wheel speed sensors to determine if any wheel is beginning to lock. When a wheel locking tendency is detected, the ABS Module commands the coils to actuate. The ABS Module command coils then open and close the valves in the HCU that modulate brake fluid pressure in some or all of the hydraulic circuits. The ABS Module continues to control pressure in individual hydraulic circuits until a locking tendency is no longer present.

The ABS Module contains a self-diagnostic program that monitors the antilock brake system for system faults. When a fault is detected, the amber ABS warning lamp is turned on and the fault diagnostic trouble code (DTC) is then stored in a diagnostic program memory. These DTC's will remain in the ABS Module memory even after the ignition has been turned off. The DTC's can be read and cleared from the ABS Module memory by a technician using the scan tool. If not cleared with a scan tool, the fault occurrence and DTC will be automatically cleared from the ABS Module memory after the identical fault has not been seen during the next 3, 500 miles of vehicle operation.