Help me identofy this connector and its purpose?

I just now opened my truck bed to install my BAK MX4 and I noticed a wire / connector that I have no idea what it is? It was tucked inside the side rail so I didn't notice till I started to install the MX4. See attached pictures.

 

Sorry, fat fingers posted before attaching pics

 

Are you the first owner of the Truck? Looks like maybe there was a camper shell on there and somebody did not want to go through the effort to remove the wiring harness for it.

 

Looks like the plug for the 3rd brake light for a cap.
Get a test light and ground the black wire and put the probe in 1 of the red wired plug and have someone step on the brake, if the 1st one doesn't work switch to the other red wire.

 

Yes first owner. I will have the dealer deal with it I guess when I take it in for my 5K maintenance.

 

Ahh, I just posted the same question today...
https://www.tundras.com/threads/question-is-this-oem.134611/#post-3411015

Everyone pointing toward it being a Leer cap just as @Jim LE 1301 indicated.

Strange you are the OG owner though. My truck is used and most are saying it's not OEM in my posted thread

 

As others stated that is aftermarket.

I'd bet if you pulled your driver's side tail light, you would see where that plug is tapped into your OEM wiring.
Unless they tapped it in behind the trailer plug...

If you don't need it, remove it and tape off where their taps are tapped in.