If your ABS warning light comes on while driving:

If the ABS warning light illuminates while driving, the ABS is malfunctioning but the conventional brakes continue to work. You can drive carefully to your destination or to a repair shop. Adjust your driving to compensate: brake earlier and more gradually to avoid the lockup conditions ABS would normally prevent, increase following distance, and avoid panic braking that could cause uncontrolled skids. The yellow ABS light is distinct from the brake warning light (which is red and indicates a more serious problem). Have the ABS repaired at the next reasonable opportunity, and note the malfunction in your inspection log. ABS does not work in reverse on most heavy vehicles regardless of fault status.