Hmm interesting, sorry for the new thread if others have already asked lol. It's only when starting and idles for a minute. If I had to guess it's meaning the truck is in open loop.
Edit: Scratch that I found the thread where they talk about it and it seems to be a software deal...
I just bought a 5.0 FX4 with the 3.31s and have about 500 miles on my truck. Im averaging about 22-24mpg lately and coming from a 19 tacoma that got 21ish on a good day I'm thrilled with the 5.0. The only thing that is slightly annoying is the auto start/stop but that's on all manufacturers...