I have a 2015 ford f150 with the 2.7 ecoboost. The truck only has 34000 miles, and has given me the same problem I am about to describe four times now. When I get on the interstate and cruise above 70mph, the truck throws a wrench light out of no where. It says check manual, and after that light comes on the transmission begins downshifting. It goes from 6th speed to 4th speed a lot. Like it struggles to maintain speed. But when I turn the truck off the code goes away and runs fine. It could be days or weeks until it does it again. I took it to the dealership and they said they can't do anything until I take it with that light on. When the truck had 22000 miles it had the same wrench light but it always stayed on. The problem then was the auxiliary transmission pump. The dealer replaced it under warranty.

 

Get a code reader, and next time it happens read out the codes immediately.

 

And if possible, take a video of the wrench light AND the code reader code. You can show it to the dealer who should fix it.