Electronic Brake Control Module: Description and Operation

Normal Condition
The anti-lock brake system (ABS) is controlled by an anti-lock brake control module located under the instrument panel. Through its preprogramming, the anti-lock brake control module decides which brake caliper pressure needs modulation. Once the decision is made, the anti-lock brake control module sends appropriate signals to the solenoid valves located in the hydraulic anti-lock actuator assembly. These solenoid valves allow adjoining flow control valves to modulate fluid pressure, resulting in a pressure reduction at the brake calipers to prevent further lockup.

The anti-lock brake control module continuously calculates wheel speed, and thus vehicle speed. The module activates the ABS only when it senses wheel lockup under severe braking conditions. If the anti-lock brake control module senses wheel lockup, it sends a pressure reduction signal through the anti-lock relay to the hydraulic anti-lock actuator assembly. The solenoid controls the flow of hydraulic fluid into a buffer chamber located in the anti-lock actuation unit.

Preassure Increase
When the wheel is no longer in danger of lockup, the anti-lock brake control module sends pressure increase signals through the anti-lock relay to the hydraulic anti-lock actuator assembly. One signal tells the solenoid to allow hydraulic fluid pressure to increase while the other signal activates the pump motor to further increase pressure by returning fluid from the buffer chamber. This operation continues for all wheels until the wheels are no longer in danger of lockup.

Fail-Safe Mode
A fail-safe function is programmed into the anti-lock brake control module that reverts the system to normal braking if a malfunction is detected. A self-diagnosis function checks for problems within the anti-lock brake system. The anti-lock brake control module stores service codes in its memory to aid the technician in diagnosing problems. The anti-lock brake warning indicator is illuminated while the engine is ON to notify the driver of a system failure.

The Anti-Lock Brake Control Module Performs The Following functions:
^ Calculates wheel speeds
^ Estimates vehicle speed
^ Senses wheel lockup
^ Activates anti-lock brake system
^ Utilizes self-diagnosis and fail-safe functions
^ Store service codes in memory