Just an fyi. My 2017 Sierra 2500HD had a glow plug failure at 60K. Got two codes. P0671 and P06C5. Ran for about a month before I got i into the dealer. They found one glow plug with high resistance and replaced it under warranty.
Second glow plug failure at 80K. Same code P0671. This time #1 glow plug. Replaced under warranty. I'll expect another failure around 100K At least I should get a bunch of them replaced before end of warranty. Truck runs great with no other issues.