Anti-Lock Braking System - General Information

Your anti-lock braking system is versatile, technical apparatus that can help you brake better and safer. It does this by helping prevent your brakes from locking up. Note: not all vehicles have anti-lock brakes. Anti-lock brakes are standard on some vehicles and can be ordered as an option on others.

Note: this is a general description. Consult a repair manual or other reference material written specifically for your truck, car, SUV or van for an exact description of your anti-lock brake system.

Your anti-lock brake system (ABS) helps maintain directional stability, vehicular steering, and optimum deceleration under extreme braking conditions on many types of surfaces. These include icy, wet and gravel-covered roads. The system does this by monitoring each wheel's rotational speed and by controlling brake-line pressure to each wheel's brakes during braking. These actions together prevent the wheels from locking up.

The ABS has three main components: 1) a speed sensor on each wheel 2) an electronic control unit and 3) a hydraulic unit. The system works like this. The four wheel sensors, one on each wheel, routinely send electronic signals to the control unit. The control unit monitors and compares these signals to its internal program, making a determination as to whether a wheel is about to lock up.

If the control unit senses that a wheel is about to lock up, it sends an electronic signal to the hydraulic unit, telling the unit to reduce hydraulic pressure (or keep it at the current level). The braking unit at the wheel receives this electronic signal at the brake caliper. Electronically-operated solenoid valves control hydraulic pressure to the brakes.

If a problem develops in the system, an ABS warning light will illuminate on your dashboard. Visually inspecting the ABS will sometimes help locate the problem. Carefully inspect the wheel sensor wiring harness. Pay special attention to the harness and the connections near each wheel. Watch for signs of chafing or breaks. This could be caused by the wires being incorrectly routed. If the wheel-sensor wiring harness is damaged in any way, the sensor must be replaced.

Warning: Do not try to repair an ABS wiring harness. Your ABS is very sensitive to even the slightest change in electrical charges. Repairing the harness could alter the electrical impulses flowing through the harness and cause the ABS to malfunction. If your ABS wiring harness is damaged in any way, replace it.

It is possible to diagnose and repair a malfunctioning ABS yourself. However, if you have any doubts or concerns about your ABS and you are not inclined to attempt what could be an involved diagnosis and repair procedure, take your vehicle to a qualified automotive technician.