2012 Tacoma 2.7 Access Cab - Tow Connection

I've owned my truck since 2014 and bought it slightly used. The 4-pin tow connection came on the truck but has never worked. I never really needed it so ignored the fact it wasn't functioning. Fast forward and I need to tow a trailer in the next week. I have the 4-pin connector and what looks like a harness plugged into my driver side tail, with a relay box. I was going to order the wiring harness to get from the cab to the rear of the truck (

$150 08921-04960 Towing Wire Harness

08921-04960) but I'm not sure if I need all of those components in the kit, or just the main wiring harness.

My confusion comes from this off plug under my driver taillight. It seems spliced into the 4-pin connection, but I think the OEM harness plug is a 4 pin.



I also have the 4-pin connector under the dash, so should be good there.

Any advice on what I need to do would be greatly appreciated. I can take more photos of the driver tail assembly if needed.

 

Anybody know what this mystery plug is? I bought the toyota OEM trailer wiring harness, but Nothing matches up with what I have on the truck. Beginning to think the 4-pin I have was an after market deal either by the dealership or first owner and not factory