Anti-Lock Control: Abs: Notes

The ABS consists of the following components:

• ABS module - attached to the Hydraulic Control Unit (HCU), but can be serviced separately.
• Front wheel speed sensors - one sensor is located in each front wheel knuckle. The sensors are serviced separately from the knuckle.
• Front wheel speed sensor tone rings - one tone ring is located in each wheel bearing and wheel hub assembly and is serviced with the wheel bearing and wheel hub.
• HCU - which contains several valves (inlet and outlet), the hydraulic pump motor and is mounted behind the battery and battery tray.
• Rear wheel speed sensors - one sensor is located in each rear wheel knuckle. The sensors are serviced separately from the knuckle.
• Rear wheel speed sensor tone rings - one tone ring is located in each wheel bearing and wheel hub assembly and is serviced with the wheel bearing and wheel hub.

ABS aids in the prevention of wheel lock-up during braking events which allows the driver to maintain steering control and stop in the shortest distance possible under most conditions. This is accomplished by the ABS module and HCU modulating brake fluid pressure to the affected brake caliper(s) and wheel cylinder(s).

When the ABS activates, the driver may notice the following operational symptoms:

• A rumble or grinding sound may be heard (HCU pump motor)
• If the driver's foot is on the brake pedal, a vibration may be felt in the brake pedal (HCU pump motor and valves)