I hear ya!
I had my Tahoe in storage. I drove 2,000 miles to go back to take it to have my emissions test done on it. My trip back was planned and I only had X amount of days to do it.
I pulled it out of storage and put a new battery in it and drove to the DMV.......it failed because of changing the battery which wipes the computer out. As will any type of engine repair. :R
They did give me a temp plate and said: "just drive it around. Going back and forth to work on the interstatefor a 'week' should re-set it. :S
Explained I was retired and in a MH and could not do that,to no avail.
Some will reset within a couple of days and some don't. When I went back for my toad emissions I had to replace the o2 sensors and when I took it back it wouldn't pass either. They said to drive it around. :R:R
I had to leave my toad up North with my mechanic and told him to drive it back and forth to work, I'd pay for the gas. It took 10 days of driving to reset the computer.