Controller Anti-Lock Brake (Cab): Overview

Fig. 9 - Location Controller AntiLock Brake (CAB):

The Anti-Lock brake controller is a small microprocessor based device which monitors the brake system and controls the system while it functions in Anti-Lock mode. The CAB is located under the battery
tray (Fig. 9) and uses a 60-way system harness connector. The power source for the CAB is through the ignition switch in the RUN or ON position. THE CONTROLLER ANTI-LOCK BRAKE IS NOT ON THE CCD BUS
The primary functions of the (CAB) are:
(1) Detect wheel locking tendencies.
(2) Control fluid modulation to the brakes while in Anti-Lock mode.
(3) Monitor the system for proper operation.
(4) Provide communication to the DRB II while in diagnostic mode.

The (CAB) continuously monitors the speed of each wheel, through the signals generated at the wheel speed sensors, to determine if any wheel is beginning to lock. When a wheel locking tendency is detected, the (CAB) will isolate the master cylinder from the wheel brakes. This is done by activating the isolation valves. The (CAB) then commands the appropriate build or decay valves to modulate brake fluid pressure in some or all of
the hydraulic circuits. The fluid used for modulation comes from the booster servo circuit. The (CAB) continues to control pressure in individual hydraulic circuits until a locking tendency is no longer present.

The (ABS) system is constantly monitored by the (CAB) for proper operation. If the (CAB) detects a fault, it can disable the Anti-Lock function. Depending on the fault, the (CAB) will light one or both of the warning lamps.

The (CAB) contains a selfdiagnostic program which triggers the indicator lights when a system fault is detected. Faults are stored in a diagnostic program memory. There are 19 fault codes which may be stored in the (CAB) and displayed through the DRBII. These fault codes will remain in the (CAB) memory even after the ignition has been turned off. These fault codes will remain in memory until they are cleared with the DRB II, or automatically after (50) ignition switch on/off cycles.