Electrical - where to begin

[Moosemoon]

I am no engine expert but did this "technician" replace your spark plugs and wires for you? Newer engines with high-energy ignitions need resistor spark plugs, electrical noise/interference may affect surrounding sensors. (like knock sensors). Just a thought.

Check your schematic, the radio and instrument panel might share a common ground inside the dash somewhere, it may be loose, corroded or broken.

Hmmm - yes I have a receipt from O’Reilly’s for spark plugs (8) and an ignition wire. I do not have a receipt for spark plug wires but was billed for them but not for the ignition wire. Go figure.
I will check to make sure they are appropriate for my Yukon.
Am studying the diagram(s) to find the ground locations for the radio an instrument panel lights.

Thank you.

no radio and cluster dim could reflect a poor connection somewhere, where exactly is the tricky part. most commonly it's the ground to the battery.
I would ohm check the ground cable as a place to begin. from "negative battery post to ground point on engine block/head" it should read 0.00
you may have a smaller cable that also splits from the main ground cable and goes to the frame check that as well.
on the back of the engine I think drivers side there is a ground strap there as well it can be difficult to reach you may want a stool or something to give you a lift up.
I know you said you checked the grounds before but a ohm test will confirm they are good

 

[Moosemoon]

Doubelieve thanks
I have checked both those grounds more than once and both grounds are good.
There is a short under the dash. I am not sure where. The heater blower motor also has intermittent success at operating.

 

[Moosemoon]

UPDATE: the shop that put in the 2nd set of knock sensors in lived up to their warranty and more - replaced bank 2 sensor and mass air flow sensor. Picked it up and had terrible whistling noise, took it back and they fixed it. Yukon running much better. Sounds like it’s old self. No knock sensor codes pending, no service engine light! Yay!

Still have airbag loop codes, brake switch, torque converter clutch, fuel transfer pump, & fuel sensor 2 codes not passed since cleared.

New code today -auxiliary ECU malfunction

There are definitely electrical things going on that the dealer will hopefully figure out starting tomorrow.

Thanks for helping me to be smarter about how to talk to these folks.

Will update as things get fixed.

 

[Moosemoon]

Dealer was a bust. 2 and a half weeks Not One Thing on MY list is fixed. They did manage to convince me that the upper control arms needed replacing and a leak in the transfer case needed sealed. (Should there have been evidence of a leak on the driveway?)
Of course it needed an alignment after installing control arms - and it pulls to the right now - not drifts - pulls.
And so it goes…. Or doesn’t

 

[Doubeleive]

Dealer was a bust. 2 and a half weeks Not One Thing on MY list is fixed. They did manage to convince me that the upper control arms needed replacing and a leak in the transfer case needed sealed. (Should there have been evidence of a leak on the driveway?)
Of course it needed an alignment after installing control arms - and it pulls to the right now - not drifts - pulls.
And so it goes…. Or doesn’t

maybe try another dealership?

 

[Moosemoon]

Went to other gmc dealer and visited with a service writer. He seemed good and gave me a quote for one thing on my list. Parts guy was good - ordered the clips and screws that I need to reattach the master switch control cover and panel under the steering wheel. Have no clue why dealer 1 didn’t do it. I will do that myself now.
There are also 2 Chevy dealers to try ….

 

[Baja_Bob]

Not all dealers have all the answers, that's why they came up with the upper control arm problem, if it were me I'd put the other problems on hold and focus on the electrical problems your having. Just my 2 cents.

 

[Moosemoon]

Not all dealers have all the answers, that's why they came up with the upper control arm problem, if it were me I'd put the other problems on hold and focus on the electrical problems your having. Just my 2 cents.

Thank you. I agree. Was hoping the dealer would work on the elec issues - not like I didn’t ask them to.
Have figured out that this dealer is an installer not a fixer. Their solution is take it out and replace and hope. They appear uninterested in tracking down gremlins and fixing.

 

[Moosemoon]

The dealer did fix the alignment issue.

 

[Doubeleive]

Thank you. I agree. Was hoping the dealer would work on the elec issues - not like I didn’t ask them to.
Have figured out that this dealer is an installer not a fixer. Their solution is take it out and replace and hope. They appear uninterested in tracking down gremlins and fixing.

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.