Same issue here. Got it back to the dealer, Banks Chevrolet in NH, before it went into limp mode due to DEF system problem. 6000 miles on new 3500 Duramax. Thankful for the GMC sierra 1500 loaner to drive around but dealer told me I cannot trailer with it and of course it does not have a rack and all my work equipment. The service advisor told me that they have six more newer trucks parked waiting with the same issue and they cannot tell me when the part will come in. At what point does the lemon law start to apply?