Same scenario. Filled up 5-6 times, no issues, filled up, started IG and CEL came on. It appears that after I filling up with gas I had unlimited range, as the fuel gauge did not move and the average expected milage was stuck at 270.
I fueled up, I cleared the CEL, and I reset the center display. The fuel gauge worked (maybe), average expected milage started to work again. Drove the IG this morning and it appears to be stuck again, both the gauge and the expected milage at 260.
I will be driving a distance today, relying on my odometer to determine fuel levels.