On my 2010 Ford I had to use a fuse and a relay that was found in the glovebox in an unmarked envelope before I could get 12VDC going to the trailer. The connection is only present when I have the truck ignition key on...
I guess the different brands of trucks all do it different...
On my Ford setup I also have a truck timer involved - maybe that is what you have too. When I turn my truck ignition key OFF and remove my keys the connection still stay connected for a couple more minutes. Then finally all of the truck interior lights and other 12VDC panel guages etc all shut down... This even happens when I have the trailer plugged into the truck 7-way connector. I lose all my trailer safety running lights when my ignition key is removed and times out. I wish that was on permanent. My older 2004 truck was that way. Someone told that may be an option setting in the truck electronics.
My truck 12VDC sockets go off after awhile as well when I remove my truck keys... I only have one 12VDC socket that stays hot all the time which is located inside my center console.
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS