Electrical - where to begin

[Moosemoon]

you might find this to be the case for all dealers, gm in general does not repair unless it is something related to a service bulletin, just how it is they would rather replace it than fix it.
there are exceptions of course.
electrical problems are addressed with a set choice of parameters, like
a=b
b=c
but if a=c then b must be no good so replace b
it's broken down in steps & procedures, bit more complex than my example but that's a general breakdown
it sometimes helps if you are VERY specific of what you want them to do and then make sure the service writer put's those specifics in the service write up.
there is often very generic or poor communication between the counter monkey and the technician actually doing the work based on the service write up.

Thank you. That is great advice. If I use a dealer again for the Yukon, I will be VERY specific. I think previously I have assumed they know so much more than I do ….
Thanks to folks here and a lot of other research, I am A LOT smarter but still a novice