Old Thread but I am having same issue on my 2015 Silverado 1500. 118k miles CEL came on flashing when I was getting on the highway. Cyl #7
I suspect it’s going to be failed lifter because of the stupid AFM.
Sucks I literally bought the truck 6 months ago. Thankfully I also did the Zurich extended warranty. Truck goes into dealership tomorrow. Truck is bone stock and I baby it. Kind of disappointing