Electronic Brake Control Module: Description and Operation

The antilock brake controller (CAB) is a microprocessor-based device that monitors wheel speeds and controls the antilock functions.

The primary functions of the CAB are:
- monitor wheel speeds
- detect wheel locking tendencies
- control fluid pressure modulation to the brakes during antilock stop operation
- monitor the system for proper operation
- provide communication to the DRB while in diagnostic mode
- store diagnostic information in non-volatile memory

The CAB continuously monitors the speed of each wheel. When a wheel locking tendency is detected, the CAB will command the appropriate valve to modulate brake fluid pressure in its hydraulic unit. Brake pedal position is maintained during an anti-lock stop by one of two methods. During an antilock stop, the pedal position is controlled by being a closed system with the use of 3 accumulators. The CAB continues to control pressure in individual hydraulic circuits until a wheel locking tendency is no longer present.

The antilock brake system is constantly monitored by the CAB for proper operation. If the CAB detects a system malfunction, it can disable the anti-lock system and turn on the antilock warning lamp. If the antilock function is disabled, the system will revert to standard base brake system operation.

The CAB inputs include the following:
- four wheel speed sensors
- stop lamp switch
- ignition switch
- main relay voltage
- pump/motor sensor signal
- diagnostic communication (CCD)
- G switch (acceleration switch)

The CAB outputs include the following:
- six valve/solenoid drivers
- main relay actuation
- pump/motor relay actuation
- check antilock warning lamp actuation
- diagnostic communication