The only sure sign of impending ECU failure is other expenses will have your wallet empty.

No, there's no warning, and if the symptoms you reported in your "dead in the water" post "opened the OBD box, started with socket #2 with the ignition key turned on, red light came on without pushing button, did not blink,when I put it into #6, red light came on while pushing button, again not blinking. My battery was very weak so it is now on charge. I will be able to try again tomorrow! " were accurate, they did not point to an ecu failure, but instead a power failure to the engine management components.

We have two 1991's and fuse 6 is where they moved one inside that was troublesome in 8 previous model years along the fender under the hood. Not that it blows, but that the contacts get poor. We've even seen evidence the fuse got hot enough to discolor the plastic nearby. There are other possibilities, but this is the #1 place to look.


--
Art Benstein near Baltimore

You know what I did before I married? Anything I wanted to.