Towing to the race track this weekend I realized my running lights stopped working. The brake lights and both turn signals work just fine, but when I turn on the truck's headlights the trailer running lights don't turn on.
Under the hood in the rear-most fuse panel I see 4-5 fuses labeled towing in some generic manner, but didn't have the time to fish it out and pull any of the fuses to check one by one; they're hard to get to.
Can anyone help me pinpoint which fuse would do this? Or if it's even a fuse at all and not some other known issue?
EDIT - My trailer has brakes and I have a brake controller installed so I have the 3 relays underhood.