P0324 - Knocking

[UpstateEMS]

2015 GMC Yukon SLE, less than 5000 miles, took delivery in June 2015. Was driving the car today and it did not seem to be shifting correctly, power loss, then Check Engine light comes on. Pretty heavy knock at idle as well. Spoke to OnStar, gave me P0324 error code. (I think this is a Knock Control System Error.)

The car is at a GMC dealer now, they are telling me that it is a "Fuel Trim Code" and that they need to take apart the top cover of the block to complete further diagnosis. Theories include a bad valve versus rocker arm problem.

I can't find anything online about this error code in the 2015 model year. Has anyone experienced this in the past?

 

[UpstateEMS]

Update:
Sure enough, one of the rocker arms failed and the needle bearings from it are missing. Won't be getting the truck back for a while.

It looks like this has been a problem in the past with the 5.3 L blocks. Has anyone else had this problem this early with their 2015 Tahoe/Yukon?