Controller Antilock Brake (Cab)
The Controller Antilock Brake (CAB) is a microprocessor-based device that monitors wheel speeds and controls the antilock functions. The CAB contains two microprocessors that receive identical sensor signals and then independently process the information. The results are then compared to make sure that they agree. Otherwise, the CAB will turn off the antilock and turn on the ABS amber warning indicator.
The primary functions of the CAB are to:
- detect wheel locking tendencies
- control fluid pressure modulation to the brakes during an antilock stop
- monitor the system for proper operation
- provide communication to the DRBIII® 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 antilock stop by being a closed system with the use of 2 accumulators. The CAB continues to control pressure in individual hydraulic circuits until a wheel locking tendency is no longer present. The CAB turns on the pump motor during an antilock stop.
The antilock brake system is constantly monitored by the CAB for proper operation. If the CAB detects a system malfunction, it can disable the antilock system and turn on the ABS warning indicator. If the antilock function is disabled, the system will revert to standard base brake system operation.
The CAB inputs include the following:
- diagnostic communication
- four wheel speed sensors
- ignition switch
- fused B+
- brake lamp switch
- traction control switch (if equipped)
- ABS warning indicator actuation
- valve actuation
- diagnostic communication
- traction control lamp illumination (if equipped)
The CAB outputs include the following: