Solution: Follow This Troubleshooting Guide

• Check alternator for charging
  Without an expensive alternator testing machine, it is hard to know with complete certainty whether your alternator is charging properly. However, this will give you a general idea. Connect a volt meter to your car's battery (positive to positive and negative to negative). Start your vehicle and take notice of the voltage output on the volt meter. If there is an increase in voltage when the car is started, your alternator is probably good. If there is not an increase in voltage, it is probably bad.
  
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• Replace ABS/Overvoltage relay
  If your alternator is charging properly, replace the ABS/Overvoltage relay. It is located in the trunk behind the carpeted panel just forward of the fuel filler neck.
  
  Note: More often than not, this will be the problem
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• Replace ABS computer
  
  Note: Although it is possible that this is your problem, it rarely fails.

Solution: If your ABS light comes on above 5 mph, you probably have a bad wheel speed sensor. Without an oscilloscope, it will be difficult to know with certainty which sensor is bad. However, you can use on ohm meter to get a general idea. Unplug the ABS sensor from the wheel. Use your ohm meter to read the level on the sensor. If it reads between 1,000 and 1,100 ohms, the sensor is probably good.