2006 Elantra. OBD port isn't getting any power.

What I've checked so far:
OBD connector: pin 16 to pin 4, and pin 16 to pin 5: no voltage on either
Fuses (all of the following checked out fine using multimeter short/open test): ROOM LP, STOP LP, C/LIGHT, S/ROOF

Additional info that might be relevant:

1. I removed the after-market stereo many months ago and left the wire harnesses to/from the stereo disconnected.
2. the upper cigarette lighter outlet has no power but the lower cigarette lighter outlet does have power.
3. the dome light doesn't turn on
4. the driver and passenger upper lights don't turn on

 

Update: In the cabin fuse box there's a black 'plug'. I pulled that out, rotated it 180 degrees, plugged it back in and all my lights and OBD sensor now work. I recall reading this somewhere online but don't know yet what that 'plug' is for. I will update when I find out.