Most ABS problems are due to ABS sensors that are not in spec. If one of the sensors is higher or lower than the other then that causes a problem. I have only replaced one ABS control unit and that was on a 190e that was corroded. Your best bet would be to bring it to a shop that has a ABS tester that can check your sensors and give you an accurate diagnosis. Guesses will cost you money, acuurate diagnosis will save you money. Good luck.