System Operation

System initialization starts when the key is turned to the RUN position. At this point, the Controller Anti-Lock Brake (CAB) performs a self-test of the electrical components. System initialization continues with a dynamic check that will test the inlet and outlet valves at 5-10 MPH. At the speed of 15 MPH, the CAB will attempt to test the pump motor if the driver does not have their foot on the brake pedal. If there is a brake pedal sense, the test will then be run at 24 MPH regardless of brake pedal position. During this test, the driver may feel some pulsation in the brake pedal. This is a normal condition.

If any component or test should fail during the self-test/dynamic test, the Controller Anti-Lock Brake (CAB) will illuminate the ABS and TRAC OFF (if equipped) warning indicators.

Listed are some of the normal conditions which may exist during Anti-Lock Brake System (ABS) and Traction Control System (TCS) operation:

• Slight brake pedal drop and pop noise when the ignition key is turned on.
• Brake pedal may pulsate during braking due to modulation of brake fluid pressure in each brake hydraulic circuit.
• Clicking or buzzing sound may be heard with vehicle at approximately 15 or 24 MPH. Clicking or buzzing sound is caused by a system test which operates the pump motor to verify proper pump motor operation.
• Groaning sound may be heard during hard braking resulting in ABS operation. Groaning sound is caused by operation of valves in pump motor to perform an ABS stop.
• Brake pedal may ratchet downward at the end of an ABS stop. Brake pedal movement is caused by opening of inlet valves in the HCU to increase pressure in the brake hydraulic circuits.
• On models with Traction Control System (TCS), a groaning sound may be heard when vehicle is accelerating until vehicle speed is approximately 35 MPH. Groaning sound may be caused by front wheel(s) slipping on the road surface and TCS operating.
• The Green traction control function (TRAC ON) light, located on instrument cluster, will remain on until traction control cycle is completed.