If your anti-lock brake (ABS) light is on and you have already ruled out serious mechanical problems, it could be that your ABS sensors are dirty. If enough dirt builds up on the sensors it will trip the lights. This will effectively undermine the warning light's purpose and you may be left unaware if serious problems to occur with your anti-lock brakes.
Purchase a repair manual for your year, make and model of car. Chilton is a popular producer of repair manuals for the home mechanic but there are others on the market. Choose one with plenty of pictures as each make and model of car is different.
Loosen the lug nuts on the tire that has the ABS sensors behind them. Jack the car up and place jack stands under the car.
Remove the lug nuts and the tire and set aside. Turn the steering wheel so that the tires face opposite from the side you are working on.
Refer to the repair manual to locate your ABS sensor. Remove the bolts that attach it to the car. There is usually more than one bolt holding the sensor in place so make sure to remove them all.
Use the towel and water to remove the dirt from the sensor once it is free. if your sensor is particularly dirty use the soft bristle brush to scrub it gently.
Reverse the above steps to reattach your ABS sensor. place the tire back on the car and tighten the lug nuts before lowering it with the jack.
