Is my ECU bad?

[greenvention]

1991 Loyale - I've had it for 5 years and keep having to fix electrical issues. First it was bad headlight relay, which thanks to forums like this I was able to find. Then the aftermarket radio was shorting out because someone just cut wires without taping up the ends or anything and I think they were contacting the housing. Well It was running great for a while, but recently I've been coming back to a dead battery again. A break light burned out, but at the socket instead of the bulb. I disconnected the group of 3 lights for that light for now, but I still get a draw on fuse 5. I think I'm getting a draw on fuse 4 too, but not sure because one meter says yes, another one says no, but both say yes on fuse 5. When I pull out fuse 5, like the actual moment of sliding, the passenger door belt surges, like the motor fires and the shoulder strap moves a little. Only when I'm pulling the fuse out.

Anyway I need to fix it because this morning I headed out on the freeway, felt some tugging, then lost power, then couldn't start. I got towed home. I fiddled with one of the parking lights that is also out (and also the bulb itself seems to be fine?), and thought I'd try starting it again and it started right up. Actually that was after I took the radio out to see if it was shorting again. Good news! Except the parasitic draw was still there and I really need to do this road trip which means I really need to find the short or bad circuit or replace the ECU is it got fried in the process. I'm still thinking it's a bad connection somewhere throwing everything else off, but my brain is not as sharp as it used to be. So I tried conversing with grok 3 for a long time and it's very logical but not great like a mechanic who knows things. 

Is there a way I can tell if the ECU is bad? Would it act intermitantly like this if it was? I used to get a CEL and after various tuneups I found a sensor, i forget which one, but one that could effectively be replaced with a resistor, which I did, and have not had a CEL since then. That was last year or so. It ran great for months before this resurgance of electrical issue. Still no CEL - which I'm guessing DOESN'T rule out that it still COULD be a bad ECU. 

If anyone has any clues, I'd love to hear them!

[moosens]

Some folks have baked their ECUs just enough to get the solder to loosen up and reset. 
 

Also check every ground for good metal contact. And if the general field that a ground lands on is a rusty area that’s not considered a good ground. Folks add ground wires. Usually see the braided type, nice and thick.

 

That would be a starting point. Good luck. Post back. 

[greenvention]

After several hours of unplugging all the plugs i could find, i finally unplugged this one and the parasitic draw dropped to zero

Any idea what it is?

Next step would be to test the pins, but I have to know what they're supposed to be before I can make any meaning out of it