Some reasons that the ABS light stays on in a vehicle are the emergency brake not going down far enough, a loss of hydraulic pressure, malfunctioning hydraulic circuits, and a dirty ABS wheel sensor. The ABS system usually generates a diagnostic code if the light has been triggered, which can be read by a service technician who can then properly diagnose the cause of the problem.
The emergency brake sometimes does not go down far enough to disengage the ABS dashboard light. Push in the emergency brake trigger, and move the handle up and down a few times, ending with the handle in the down position. If the vehicle has a side handle emergency brake, try pulling the release lever.
A loss of hydraulic pressure is another common cause of the ABS light being activated. Check the fluid levels in the brake fluid reservoir. If a significant amount of fluid is missing, it may be indicative of a leak causing a loss of pressure in one or both sides of the vehicle. Loss of hydraulic pressure causes brake failure, especially at higher speeds, and should be remedied as soon as possible.
Check that the ABS wheel sensor is not dirty or obstructed by first removing the wheels and locating the sensor. Remove it by loosening the bolts that attach the sensor to the vehicle's frame, gently wipe the sensor clean, or replace the sensor if it is damaged.