This guy describes exactly what the DLC3 connector in the Highlander does when I try to plug into it.The car doesn't sit long enough to have any self-discharge issues.
Not to take this is thread into another direction, but look what I found tucked into the kick panel of the Highlander. Is this really a tracking device?
What made me look closer was the DLC connector housing in the video is black as is mine. When I was looking for a replacement housing, the OEM Toyota part is white.