Make sure your truck is configured to provide power. Over the years a variety of things may or may not need to be added or connected to make this function work. Was all dependent on Brand and model year. Some needed a wire connected under the hood, or under the dash, or a relay added, or a fuse added, or all of the above.
I cannot speak for other trucks.
The first time I towed my 5th wheel home the dealer activated my trailer, however they choose my boat trailer configuration. My boat trailer doesn't have a battery, and thus power was not provided from the truck. It was a 4 hour drive home. When I got home I checked my 5th wheel battery charge, 1/4. It was full when I left. My 12v fridge was on the whole trip.
First camping trip with the 5er I configured the trucks trailer setting for a 5th wheel and then the power was provided to the 5er. I drove 2 hours to the campsite, with the 12v fridge on, and arrived with a full battery and cold beverages/food.
I have a 2016 F150 with towing package. I can configure up to 10 different trailers. Note, both my 5er and boat use 7-way RV plugs. I added back up lights to the boat trailer and decided it was easier to use one type plug. Cost me a little more up front, but has paid off over time. I use the backup lights to launch and retrieve the boat at night, plus it makes backing into a dark campsite or garage easier.
Just because your truck can charge the battery, doesn't mean that feature has been activated. Test it. Mine won't work until I apply the brakes. What does Toyoda require?
) Good question
