I have a 94 - my Abs light is on - I have had the same problem- its like a vibrating kinda grinding sound and the pedal doesnt feel like it wants to go down all the way - *if we have the same problem*-
what happened, was one drizzly morning had to step hard on pedal and noticed that my left front locked up - so i checked the abs line and when i took it apart the Plastic casing around the two medal prongs basically was rotten and crumbled - i was like

so i just stuffed a but of electrical grease in there and it took a while but i got the two prongs to sit back in the socket - the light still on, but i havent had the pedal problem in awhile *knock on wood* I didnt want to risk doing it to the others left them alone
Maybe this will help
Hopefully there will be some answers