Removal & Installation
The ABS control module is integrated with the hydraulic control module. See Integrated Control Module (HCU and CAB).
The Controller Antilock Brake (CAB) is a microprocessor-based device which monitors the ABS system during normal braking and controls it when the vehicle is in an ABS stop. The CAB is mounted to the bottom of the HCU. The CAB uses a 25-way electrical connector on the vehicle wiring harness. The power source for the CAB is through the ignition switch in the RUN or ON position. The CAB is on the CCD bus.
The primary functions of the CAB are to:
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 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 CAB command coils then open and close the valves in the 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 lamp is turned on and the fault 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 a scan tool. If not cleared with a scan tool, the fault occurrence and DTC will be automatically cleared from the CAB memory after the identical fault has not been seen during the next 3,500 miles.
The Hydraulic Control Unit (HCU) and the Antilock Brake Module (ABM) used with this antilock brake system are combined (integrated) into one unit, which is called the Integrated Control Unit (ICU). The ICU is located in the engine compartment below the air cleaner housing on the lower radiator support.
The ABS with traction control ICU consists of the following components: the ABM, eight (build/decay) solenoid valves (four inlet valves and four outlet valves), two traction control solenoid valves, two hydraulic shuttle valves, valve block, fluid accumulators, a pump, and an electric pump/motor.
The replaceable components of the ICU are the HCU and the ABM. No attempt should be made to service any components of the HCU or ABM.