I had my ABS unit rebuilt by Cardone ($1,100) and the car stopped fine for about two days.  Then the ABS light came back on.  Now my former Pontiac dealer mechanic says a relay in the unit is defective and that the part is no longer available.  Does anyone have any suggestions?

Well, its just a relay, it shouldnt be hard to adapt some other type of relay in place of it. Theres usually just a trigger and ground, and a main hot, and the Load which is the pump. just be sure the relay you use has a decent amperage rating, like 20-30 amps. Relay is just a safe reliable way to control something, the abs pump in this case. So the trigger is usually from the low pressure switch, and is hot, it goes through a electromagnet inside the relay, and through to ground, that causes a switch to flip inside the relay, making the main hot go to the pump. Very simple, your mechanic shouldnt have much trouble making something work.

thanks for your help