Had this vehicle for about a week. Bought it well below NADA so I thought I would give it a try.
4th day it kicked up the CEL and some codes. 5th day the same. Both were after a 45 mile drive to a neighboring town in mid morning. Both times the codes popped up on the start of the drive home in the late evening.
I'll post some screen shots.
thanks for helping out.

 

https://www.greenhybrid.com/forums/f...22/index7.html

Read everything Hillbilly says.

Those combinations of codes are almost certainly the hybrid battery.

 

I am very interested in the diagnosis and successful repair, please follow up and let the forum know.
If I were you, right now I would be researching every known 2008 Yukon Hybrid TSB (possibly std Yukon TSBs) just to eliminate things like the wire chaffing issue.
Obviously the traction battery is suspect but that is one expensive piece to choose to "part change" with LOL .

 

Rather than a shotgun blast search of desperation fueled by hopeium to try and identify a failure mode that has never happened before, invest in the $5 software a $20 code reader and almost any Android phone/tablet made in the last 5 years and LOOK INSIDE the battery:

https://www.greenhybrid.com/forums/f...results-31736/

 

After removing the plastic and carpet panels and vacuuming the fan intakes. Intakes a little blocked .
This morning no start and "Service Hybrid Battery"
No codes.
Guess it's time to research batteries.
Thanks all I'll let you know if the battery cures everything

Update. The master battery disconnect lever wasn't pressed all the way down well. Discovered that when I took it out and put it back in. When pressing the lever down after rocking it up, it went down farther than it did originally.

I was able to start it up and drive it. Drove up the street to the big church parking lot and drove around till I got the temp up to normal operating temp. During the many stops to enter auto stop and accelerate forward trying to keep it under battery propollsion as long as possible I had the vehicle die and come to an abrupt stop. It did this on my wife the second time it kicked a code.
It restarted ok and I continued with the stop and starts. Tried to die once more but didnt. Sometimes it wouldn't even make it to 10 mph before the ICE would kick in while being very gentle on the accelerator.
I think the writing is on the wall but I'm still playing with it.

 

That is NOT a happy battery!

 

Hillbilly
Its not happy because of what I was doing to it or because its terminal?
thanks

 

Would be great if you could get the readings from inside the battery. Looks like the best tool is an actual GM Tech2 scanner. I am seeing some alternatives but it looks to involve a lot of research to pull together all the pieces/parts and then fiddling with PID codes to make it work and the results appear to be only marginal. I may just order myself a Tech2 for Christmas.....................

 

http://a.co/d/bn9hxEf

This was my solution to Tech 2 functionality, without the Tech 2 price $$$

 

New Hybrid battery solved the problem it appears. Running flawlessly.

Now to replace one of the TPMS sensors.

Thanks