sounds like my car. fisrt thing you try is bleeding the abs (not the brake calipers, it's different) see if it will start working. chances are it will work for a while. you probably need to replace the accumulator. i was trying to wrestle the entire abs unit out of my gsr yesterday so that i could put it in my ls. it's a pain in the cuz the gsr is crashed so i have less room to work with.