Brand new 2020 GMC Sierra 1500 same problem. I am researching this for my brother in-law. His description is exactly the same. Vehicle will turn over but will not start. Dealer had him shift to neutral from park, and truck started and ran fine. He drove it to the dealer and dropped it off to have it looked at.
Same story from Dealer, no error codes, they had no idea what to fix so "come get truck" and drive it.
It has done this (3) times now in the last 2 weeks. No rime or reason. Once in the garage at home, and twice trying to leave work.
After the 3rd time they are now replacing an electronic control module, for the fuel pump but are not sure it will resolve the problem.
Pretty frustrating to have a brand new truck and have this kind of problem withing the first month of owning it.
