Operation

OPERATION

The primary functions of the Controller Antilock Brake (CAB) are to:

- Monitor the Antilock Brake System (ABS) 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 mode.
- Store diagnostic information.
- Provide communication to the DRB III(R) scan tool while in diagnostic mode.
- Illuminate the amber ABS warning indicator lamp.
- Illuminate the brake assist (BAS)/electronic stability program (ESP) lamp on the instrument panel when a traction control event occurs.

The CAB constantly monitors the Antilock Brake System for proper operation. If the CAB detects a fault, it will turn on the amber ABS warning indicator lamp and disable the Antilock Braking System. The normal base braking system will remain operational.

The CAB 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 CAB commands the CAB command coils to actuate. The coils then open and close the valves in the Hydraulic Control Unit (HCU) that modulate brake fluid pressure in some or all of the hydraulic circuits. The CAB continues to control pressure in individual hydraulic circuits until a locking tendency is no longer present.

The CAB contains a self-diagnostic program that monitors the Antilock Brake System for system faults. When a fault is detected, the amber ABS warning indicator lamp is turned on and the Diagnostic Trouble Code (DTC) is then stored in a diagnostic program memory. These DTCs will remain in the CAB memory even after the ignition has been turned off. The DTCs can be read and cleared from the CAB memory by a technician using the DRB III(R) scan tool.

CAB INPUTS

- Wheel speed sensors (four)
- Brake lamp switch
- System and pump voltage
- Ground
- ESP OFF switch
- Diagnostic communication

CAB OUTPUTS

- Amber ABS warning indicator lamp actuation (via CAN BUS)
- Instrument cluster communication (via CAN BUS)
- BAS/ESP indicator lamp
- Diagnostic communication