Anti-Lock Brake System - TEVES Mark 20: Operation: Notes

When brakes are applied with normal to moderate pressure, brake fluid is routed from master cylinder through HCU to wheels, unrestricted. During heavy breaking conditions, brake fluid pressure is modulated through 3 separate channels in HCU to each front wheel individually and to rear wheels through one channel.

When stopping conditions activate the ABS system, hydraulic pressure is controlled to all 3 circuits separately. ABS system can build or release pressure at each wheel front wheel or both rear wheels, depending on signal generated by wheel speed sensors. ABS is operational with vehicle speeds of 12 MPH or more.

Amber ABS warning light is controlled by CAB. CAB along with Hydraulic Control Unit (HCU), is located under air cleaner housing near master cylinder. CAB controls ABS warning light by grounding circuit.

ABS system initialization starts when ignition switch is turned to the RUN position. At this point, the CAB performs a complete self-check of all electrical components in ABS system. At about 12 MPH, wheel speed sensor circuitry is checked, and the ABS pump motor is briefly activated to ensure operation. If for any reason brake pedal is depressed when vehicle reaches 12 MPH, this check will be delayed until vehicle reaches 25 MPH. If any component exhibits a trouble condition during system initialization or dynamic check, CAB will illuminate ABS warning light.