The mystery harness.......
 

Can anyone tell me what this harness is used for? Found it in the glove box of my 2018, without a bag, etc. Thanks.

https://cimg7.ibsrv.net/gimg/www.f15...3769cf9b02.jpg

No part number on the back of the black brick?

We usually find an aftermarket brake controller wiring harness in the glove box. What you've got looks more like a relay or sensor.

That could be the trailer battery charge relay that should have been installed before delivery. Usually the only item left in the glove box is the cap for the tailgate camera harness that is used when the tailgate is removed.

I remember reading something about that awhile ago, but of course I can't find the post now! Need to look closer at it with my glasses on and see if there is a part number as Flamintaco suggests.

When I got the 2012 F150, there was a relay in a bag, along with instructions on where to plug it in, which should have been done by the dealer. It plugged directly into the relay panel and didn't have a harness on it like yours, but my guess is it serves the same purpose.

I don't think that's a relay. How many pins in the connector? Any relay will have at least 4. It looks more like an annunciator/buzzer.

Newer trucks do not use these relays. Everything is built into the trucks electronics. Those were just a relay without a wire connected. The wiring harness was for a brake controller pigtail.

The part the OP posted is NOT a brake controller harness. Those either have a connector on both ends, or one end and bare wires on the other. What is posted could be something that got left behind during assembly and has nothing to do with towing, could just be a dropped part. Seen that before too. For all we know, it could be for the HVAC.

Thanks everyone. Still a mystery though. Looked it over and there isn't a marking anywhere on it....no part #, nothing.
they're are only 2 prongs connected to a red wire and a black one. The wires run to the black cube which is sealed.
https://cimg9.ibsrv.net/gimg/www.f15...08232412e9.jpg
https://cimg2.ibsrv.net/gimg/www.f15...fb5fd3b728.jpg
https://cimg0.ibsrv.net/gimg/www.f15...8d28b66c5c.jpg

Was any aftermarket equipment installed. Possibly a tracking device or the like?