Hello,
I'm helping a buddy out with his 2007 Avalanche, 5.3L. Problem just started out of the blue. The truck will not shift out of 1st gear without lifting off the gas. Doesn't matter if you are WOT or just normal driving. The other gear changes are fine. There isn't a CEL. I have attached a log file and the current tune file. Any help would be appreciated.
Current Tune file 12DEC2019.hpt
19-12-12 18-39-49.hpl