Lincoln/Mercury Repair: 1994 mercury marquis brakes, mercury marquis, abs brakes

Question
having problems with my brakes...had mercury in shop for brakes advised them that some times when going slow, like pulling up to a stop sign the brakes grab and groan, I also notice that when going slow ...like turning into a parking spot the brakes grab, first they put on a new brake booster, that did not work they then put on a new master cylinder that did not work they had my car for a week did not solve the problem, I have been told that the abs brakes have codes to set them up  and you have to go to a dealer, to get this done is that correct. please help  

Answer
hello rick
well rick from the start it was in the abs system . the master cyl did not have to be changed or did the boster need changeing . it was in the abs system they should have done a diagnostic test from the start . they were guessing with your wallet . tell them they should pay for the dealler to straghten the abs it is wroang what they did pete