Rear End Electrical Plug to Nowhere

While checking out the rear undercarriage, I discovered an electrical plug that dead ends into a cap that is mounted to the frame. It is located behind the rear bumper and just to the driver side of the license plate light wiring. (See white arrow in first photo.) This is not the factory plug for the trailer wiring harness because that is much larger and all the way over on the driver side. (Plus we already have a 4-flat harness plugged in there!) I pulled the whole assembly off the frame, opened the cap, and took a photo of the connector and the wires on both sides. I took these photos to the dealership parts department, but they couldn't find it on their diagrams. Any ideas?

 

Is there one on passenger side ?
The one you are showing, is it grey in color or black ?

 

Did the 1st Gen have a backup camera? That looks like the connector my '07 had for the backup camera. I used it when I added an aftermarket stereo with backup camera, my truck didn't have the factory camera so I had to modify the plug at both ends. Maybe @Roman can clarify if he can access the 1st Gen wiring diagrams or part numbers.

 

You stole my avatar...

 

With 4 pins in the connection.. it probably trailer wiring hook up from factory..

 

Here are pics from my 2002 w/factory tow package.

 

This plug is grey and I did not see another one on the passenger side.

 

Do you happen to have a part number for that harness?

 

Rear combination light LH is what shows up on the fsm

 

True....if this was a 4 pin.
From my seat it appears to be a 6 pin part # 90980-10988
Toyota colors are usually....
light blue=right
yellow=left
wh/blk=gnd
red=backup lights
can't remember red/blk ?

 

Yes! That's the correct plug and the wire colors!

 

Why would you have an extra one with a cap on it??

 

I think @Professional Hand Model hit the nail on the head: It's a factory plug for a factory 4-flat towing wire harness. Can anyone get me the part number for the harness?

 

Similar to PHM, I have Tow Package on 2004 and believe that's what yours could be used for. Wanted to check this earlier but weather sucked but the below pic one is the same location of yours and the second pic is the connectors away from frame showing it going to tow package harness plug.

 

Thanks @BubbaW ! Since yours is a later model, looks like you have an additional factory connector beside it to supply the remaining wires required to run a full 7-way plug.

 

Pretty sure you're right and tried to look and count colors but vertigo kicked in too quickly to be for sure.
I feel you have found the needle in hay stack and with a VOM you could verify the voltages present when checking turn signals/backup/brakes.

 

Can’t find part # (probs due to it being ‘factory dealer installed’).

Edit: Two screws and a plug at dealer. You may have better chances at a salvage yard.

 

Ha Ha, great minds think alike. There, fixed it, went back to my last one.... I'll find a different one....

 

not sure but maybe a plug for towing trailer wire harness. If you are not the original owner it is possible the previous owner took their wire harness for their trailer to plug into their new truck.

 

So, it's been a few months and I thought I'd share what my dad decided to do. Ultimately, he removed the larger harness that came with the truck that was providing a partial 7-way trailer connection. (A true 7-way is not possible on this Tundra generation without extensive add ons.) He went back with a factory 4-way trailer harness using the "mystery plug" and where the connector bolts to the underside of the bumper.

 

I have a 7-way connector on my '00. The 4-way connects to it to handle the turn/stop signaling. Then run power from the brake controller, and from the battery. Same as any other truck without a pre-wired tow package.