07 trailer light plug problem

Hello, I have a problem on my '07 with my factory installed tralier light plug. It has been fine for years and then I noticed that the tralier lights are staying on all the time now. Even when the car is turned off.
Is this a grounding issue on the car itself?
I put one of those tester plugs in the receptacle of the car and the "Tail Light" lamp is lit all the time so I know the problem is on the car side.
Any ideas?

Thanks!

And do any of the rear lights on the car stay on, such as brake lights?

They all work fine but the interior light (center, top) does not come on now when the door is open but it will if you use the switch on the dash, so the buld is not burned out.

Check that the ignition switch circuit 1G1 is shutting off. This supplies power to the 15A trailer fuse. Try pulling the 15A trailer fuse and check what happens.Turn signals,tail lights,back up light,stop light give power to trail lamp circuit. Kia has had some recalls on brake lights. Call dealer and ask if you had any recalls.