I've been driving on this same tune for probably 500 miles without issue and it's been running great. Today I had to take a 45-60min ride on the turnpike, and when I got off the highway the truck started running bad. The pcm was commanding a ton of fuel for no apparent reason. Since I was away from home and without a laptop I just disconnected the O2s and ran it home in open loop. When I got home I plugged in the O2s and looked through the scanner and I see my LTFTs were stuck at 25. Everything else appeared fine. I went into the vcm controls and reset the trims and now it runs great in closed loop.
So what would cause this, besides an obvious problem, which I don't see? Also the O2 voltages are both swinging like they should so no apparent issue with them. STFTs are +\- 3% or so.