Basic System Operation

When brakes are applied with normal to moderate pressure, brake fluid is routed from master cylinder through HCU unrestricted to wheels. During heavy breaking conditions, brake fluid pressure is modulated through HCU to each front wheel individually and to rear wheels through one channel.

During an ABS stop hydraulic pressure is controlled to all 3 circuits. ABS system can build or release pressure at each front wheel or both rear wheels, depending on signal generated by wheel speed sensor.

Amber ABS warning light is indirectly controlled by CAB. CAB, along with Hydraulic Control Unit (HCU), is located near air cleaner housing. CAB controls Amber ABS warning light based on messages sent over the PCI bus.

When ignition is turned on (system initialization), Amber ABS warning light is on until CAB completes its self-tests. At 18 MPH, a dynamic check is performed. If any component exhibits a trouble condition during system initialization or dynamic check, CAB will illuminate Amber ABS warning light.