Today on the junkyard I pulled a rubber conduit that is covering tailgate to the body wire harness (mine was dry and torn). In order to install it on the wire bundle, I had to remove harness to body wire connector #801 (accessible under left taillight cover) and remove all wires from it (to feed them trough the rubber conduit). I will not bother forum readers about my incompetent efforts if all wires will be different color. However, there are two identical black wires and other two identical white/black wires are going to this connector. Traditionally most of us will assume that same color on the same connector means the same circuit. WRONG, WRONG, WRONG!! These wires are belonging to different circuits and I forgot to mark their location!!

Tailgate harness connector:

Wire color Circuit
Black ?? (ground or defogger +)
Black ?? (ground or defogger +)
White/black ? (brake light + or pwr lock)
Light green Rear wiper
Empty cavity ----
Yellow Power lock
White/black ? (brake light + or pwr lock)
Dark green Rear wiper
Red/ black Licence palte lights
Dark green/red Tailgate switch
I was super lucky that I got all reattached correctly (although my high mount brake light was burned out, which added some confusion). I also noted that some wires had cracked insulation (so 10 year old Fit will have the same problem as 20 year old Camry with broken trunk lid wire harness). So be prepared to have a solid excuse if pulled over for non –working license plate lights.
Based on the circuit analysis, here is what could happen, if I wouldn’t be so lucky:
If White/black wires are switched around and lock switch is activated:
The tailgate lock will not work
The high mount brake light will blink
If black wires are switched around and defogger is off:
No items on the tailgate will work, except the lock (missing ground)
Other not so nice outcome is also possible.
So please mark location of the wires before removing them from connector even if they are same color and size!!!

 

After some investigation, I've found that:
The White/Black wire located in vertical row below yellow wire is for tailgate power lock (can be either +or -, depending on operation)
The black wire at the corner cavity #10 is the ground wire
The black wire next to it in cavity #9 is positive feed for defroster
The remaining white/black wire is positive feed to high mounted stop light.

The power of incompetent engineering which lead to Fukushima!