The antilock brake control module counts the number of revolutions each wheel makes to determine whether the brake at each wheel is operating correctly or if it has locked up. If the brakes lock up, the antilock brake control unit releases the brake pressure applied to each wheel until the unit determines whether each wheel is contributing the correct amount of braking effort.
The ABS control module is located either in the passenger compartment of the vehicle behind the dashboard or in the engine compartment. To replace the control module, a technician unplugs and removes the old one and replaces it with the new control module. On newer vehicles, the module may need to be "programmed" before the vehicle is driven.
Antilock brakes (ABS) are a safety feature that prevent the wheels from locking up while braking. If a wheel locks up during braking, it no longer helps to stop the vehicle.
Brake fluid naturally absorbs moisture from the surrounding air. Moisture is the enemy of any hydraulic system; it lowers the operating efficiency of the brake system and may result in costly repairs if not periodically replaced.
Mechanics Corner: More Technical Detail
The ABS control unit only releases the brake pressure to the particular wheel that is locking up; wheels that are not locking up will not be affected.
The first step in replacing any onboard computer like an ABS module is to disconnect the battery. If you replace any control unit with the battery connected, there is a real possibility that the control unit will be damaged from an electrical surge or "spike."