NHTSA Complaint #11671134 — 2013 GMC YUKON

Vehicle equipped with 6.2l v8 engine. Have been experiencing hesitation upon acceleration, decrease in power/reduced performance, trouble starting, abnormal shifting (particularly from 2nd to 3rd and 3rd to 4th gear) for about two months. On two separate occassions(once about 1yr ago and the second time about a week ago) during normal use of the vehicle, the car started to shudder and the CEL began flashing. Both times I immediately pulled over and shut off the vehicle. Fluids were good, car has never overheated, regular maintenance has been performed as well. When I turned the car back on, the light was off and didn't show any signs that there was an issue. Two days ago during normal use of the car at about 35mph, a loud knocking/ticking sound started. I was about 1/8 mile from my destination so I attempted to make it there. Driveway is uphill and when I accelerated to get up the hill the sound got much louder and ticking was twice as fast. Shut off the car, let it cool, and knocking sound was just as bad the next time I started the car. Had the car towed to prevent damaging the vehicle further. This car is financed and i have three payments left on the 54 month contract. Today i reached out to the dealer about the issue and asked if I should bring my car to their service dept. I explained how i have been experiencing most of the issues that GM has identified as warning signs that indicate a potential engine failure and I was told theres no way my car has a recalled engine and the guy laughed at me when I tried to give him the information I found on the NHTSA website. Not really sure who I'm supposed to call to get some help with this issue.