System Overview
CONTROLLER ANTILOCK BRAKE/ANTI-LOCK BRAKE MODULEThe CAB/ABM is a microprocessor-based device that monitors wheel speeds and controls the antilock functions. The CAB/ABM 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/ABM will turn off the antilock and turn on the ABS amber warning indicator.
The primary functions of the CAB/ABM are to:
^ detect wheel locking tendencies
^ control fluid pressure modulation to the brakes during antilock stop
^ monitor the system for proper operation
^ manage traction control functions
^ provide communication to the DRBIII(R) while in diagnostic mode
^ store diagnostic information in non-volatile memory
The CAB/ABM continuously monitors the speed of each wheel. When a wheel locking tendency is detected, the CAB/ABM 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. The CAB/ABM continues to control pressure in individual hydraulic circuits until a wheel locking tendency is no longer present. The CAB/ABM turns on the pump motor during an antilock stop.
The antilock brake system is constantly monitored by the CAB/ABM for proper operation. If the CAB/ABM 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/ABM inputs include the following:
^ diagnostic communication
^ four wheel speed sensors
^ three power feeds: valve, pump, and microprocessor
^ brake lamp switch
^ traction control switch The CAB/ABM outputs include the following:
^ ABS warning indicator actuation
^ 12 volts supply to wheel speed sensors
^ valve actuation
^ diagnostic communication
^ PCI bus communication
^ traction control lamp illumination