actually it is quite a normal problem. this is one of the things that have been a problem throughout the years. it is a little pricey to fix. the pedal pulsates at a low speed? same problem here... at least you know that the ABS is working. not something that has to be fixed and not something that will fail as a result... has been a problem on the 190E all the way up to the S500 but not too sure of the newer ones. this is for the 80's and early 90's models.