I understand your frustration with the 2011 gmc 3500 trk. I had the same problem with our 2011 also. It was in numerous times with the dealer replacing both sensors, reprogramming it. Finally went to a differant dealer who had a 2015 that was 2-wheel drive, which I was not sure I wanted but he made a real good offer. Bye bye 2011.
A year later the dealer still has my 2011 and it stlll is giving the same error message. Good luck!!!