I get my truck back today. It's a 2016 GMC 3/4 ton Denali 6.6 diesel engine, 47k miles. In the past 2 years the check engine light has come on at least 10 times. It was usually an air sensor or rich fuel mixture code. They fixed it, it was under and still under warranty until the end of October.
A few months ago I took it in and had words with the service manager. It got them to call and work with the GM engineers. They had the truck two weeks (a slow back and forth process with the dealer) and changed all the air sensors. It worked great for a few months and then the light comes on again.
I took it in and again had words with the service manager...Is this how all diesel's you sell perform, is this normal, what are you going to do when my warranty runs out because you can't seem to fix the problem, etc...
This time it was rich fuel mixture. It's one we've already had a couple times. They called GM again, and again had the truck two weeks. This time they changed all the fuel injectors. Hope I'm done with GM service.