95 Gp

My brother has a black 95 GP and his antilock brake light stays on all the time. Does anybody know what to check with that. he's had it in a shop before and they weren't able to fix it. My bro would love the info if anybody could tell us, he has babied that car since he bought it, it's only got like 45,000 for a 95, (his play car). Cant seem to figure out what's going on with it. help please!!!