BCM..TCM..Ground problem..HELP!

[Toad]

3 months ago, my 2009 Yukons dash lights, gauges, warning lights AND doorlocks simply freaked out. Lights linking and locks slamming closed and open..This happened twice, with the engine cutting off the 2nd time. The condition (both times) only lasted a few seconds, then returned to normal. I did some research and replaced both battery cables as well as the main fuse (cleaning everything perfectly) I also added a ground cable from the alternator bracket to the same firewall location the factory battery grounding strap went to. That was fine for about 2 months, then the same crazy thing happened again. This time 800 miles from home. Luckily it again only lasted a few seconds and I completed the journey without further incident. Now I have 2 separate mechanics with differing opinions..BCM, TCM, and “some kind of ground fault”
I have fair mechanic skills and wish to get to the bottom of this w/o having to throw 3K worth of parts and diagnosis into this car.
Anyone have similar problems/solutions?

 

[Doubeleive]

you might try pulling the fuse box and cleaning the contacts

 

[97audia4]

Check your terminals at the battery. Everything you just described happening is exactly what happened to me and it was loose terminals on the battery. Tightened and it fixed everything.

 

[Kraig]

When you added the ground strap, did you clean that grounding point before attaching it? I’d probably check the battery, add another ground from the battery to your alternator grounding point, and try again.

 

[Doubeleive]

 

[63Blackseries]

Ive have had this problem in my 2013 chevy Avalanche and have not found the problem to it yet, but it seems like it happens more often in the winter time, since then i havent had the problem.