Ok!

I can except that as the conclusion to your problem!

Now I want to know did you go through the whole routine, that I laid out as a troubleshooting direction your way to the ECU?
Or did go directly to Remove & Replacing the ECU before you saw what I wrote about what number you had in there?

I still would like to know what the main number is on the bad ECU! Like 561, 933 or 955, ect.

Along with any other main label information. More numbers or colors!
There are some other odd numbers, like bar codes numbers or even production run numbers might be helpful. Labeled or stamped into metal numbers and letters.

Since it's bad you might open it up and note any information directly on the circuit boards. REV B, C D, ECT.

Even a photo of the bad guy might be some help to notice a production change like the amounts of solder on the traces or the lack of in certain places.
We know how cracks show up in joints, of these relays and speedometers all the time!

If we have enough failures documented and enough manufacturing production run codes available, that we might be able to narrow the failures to batch lot and a specific fix for them!

This might be a case of simple "batch run" of bad transistors or capacitors on the boards. This would be good information for cheap fixes to many, many, ECU's!

I believe that, Many, have failed and they are just laying around.

Since this one, is a known bad boy, it still can have one more useful thing it can do for us!

Beside it's parts there is more importantly "breakdown" information.
A "Mileage line call," gives us an even better maintenance schedules references, that can be built up into for recommending timed replacements or repairs!

It's those and any future ones that are going to be needed in the years to come for BrickBoarders!
P&P yards are drying up!

We are very grateful for you to follow up with your "fixed" post!
So many never come back and that ("what ever happen") data is lost.

Thanks again! ):-)
Phil