Found a loose wire harness while running wires through the firewall. No idea where it goes.

I'm running wires through the firewall for the first time for my lightbar and on board air switches, and when I removed the kick panel I found this harness not plugged in to anything. Any idea what it's for or where it goes? I bought the truck used so I always assume the worst from the previous owner.And this is where it plugs into:

 

Yeah that looks like it to me. So I guess I can take it out?

 

On my SR5, there are 2 harnesses unplugged on the left side and 3 harnesses unplugged behind the center HVAC console. The engine bay is the same way; there are a few harnesses unused there too.

Don't stress if something is not plugged in and everything is operational -- the harnesses in the Taco are fairly universal cross-trim, so all packages will end up with some unplugged. If that is the brake controller harness posted above, I'd just leave it in case you need to hook up a trailer brake control eventually. It's not hurting anything.

 

That’s from a brake controller. You can leave it or unplug it and fish it out.

The Tacoma is prewired (the large plug) so you just need the wiring harness (what you found) to plug into the Tacoma and brake controller.

 

No harm to leave it plugged in and tucked away. Looking to purchase one myself, same part number, for my Taco.

 

You must have bought the truck used... as that is the adapter harness that goes between the brake controller and factory harness.

 

Trailer wire harness for sure.