I purchased a new 2014 Sierra, should of known better...dummy.
First year or two of a model change brings issues!
Once you discover a problem your at their mercy!
Anyone that buys a new model design 2019, beware there's a huge potential for problems if it's anything like the 2014 model change.
As for GMC being professional grade....not in my opinion, its simply an advertising slogan.
Hope this alerts a few people! Their problems are now mine to repair.
Sure glad the American public was able to bail them out a few years ago!