Welcome to the forum! I believe that code is for a faulty glow plug controller. That should be covered under the emissions warranty if you look in your warranty book. I don't think it is that hard to change seeing that alldatadiy.com says it gives about a half an hour labor for it. I don't have a picture of it off there...it doesn't even give a part number for it.
2016 GMC Sierra 2500HD Denali
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