Is it a grounding cable? it’s under the passenger side

where does it connect?
thanks

4.6
xtl v8

 

That goes from the body to the frame you should see a bolt hole on the frame near by

 

Yep that's a ground. As mentioned look for the threaded hole nearby, clean it well and reattach.

 

See attached.
First photo shows where the ground strap attaches to the frame. You need to look, probably opposite side of frame, for the small square hole for the lug protrusion to fit into. Likely obvious when you look on the other side of the frame rail.
Second photo is the same end of the ground strap as your photo.

 

Edit
Duplicate posting deleted, see above.

 

Thank u

 

Fixed. Thank you

let’s see if I notice a difference

 

While I feel sure Ford does not put extra ground straps on their trucks for looks, I doubt you will notice any difference BUT if you do, please report back.