I towed the pop up camper 6 hours from Denver to Moab,then back4 days later. No warnings while towing but today, in the snow, Trans light while going slow in second downhill for about a minute.
I just did the transmission filter and fill last month. Was planning on checking transfer case fluid soon and topping up since I noticed a new leak from the area.

On a side note, I had to shift to low for about 4 mins to make it over over 11k foot pass. So much flooring on this trip due to the altitude. Trailer weighs about 2000# loaded

 

You do know temp sensor at bottom of cooler where it's exposed to slush etc?
May want to check fluid level to ensure good and/or do another drain/refill sans filter.
......

 

The temp sensors are known to fail.
I had to replace mine a few years ago.