Cadillac can get the codes for you. It takes a special pinout box to pull them. You can pretty much diagnose it your self. If the light comes on after you start it and before you take off, one of the computer components did not check out. Im meaning in the hydraulic assembly. If the lights dont come on until you take off, then its either a wheel sensor or the pump motor. I have soon oodles of these cars have bad relays. I just helped a guy yesterday on this and his relays were bad. He swapped them out with the radiator fan relays just to find out that the High speed radiator fan relay was bad. He replaced all four relays and everything is working good. Same way with TRU, that is one here. His sixty special was the same way.
Thanks
Blaze