I combed through a few similar topics, but my situation is a bit different, based on the cause, I think.
I rented a large U-Haul trailer, and pulled it for a total of 30 miles or so. I used the TOW/HAUL mode for this. Since then, the transmission temperature gauge indicates 250F while running. When I turn the key back one click, the transmission temperature gauge shows a "normal" temperature around mid-range. Fluid level is normal, etc. etc.
I've driven about 85 miles since I noticed this problem - too afraid to drive it any farther. Any ideas what this could be? I'm hoping that it's just a bad sensor. . .