2009 suburban 1500 2wd, 5.3 gas .....

I found a random red wire with a black stipe on it with a ring connector as if it were a ground not connected to anything I was just under the hood trying to find the fuel pressure regulator since this engine seems to not be like any other 5.3, and I came across a dangling wire that intersects the loom going to the back of the relay/fuse box... any ideas guys?

 

It looks like it comes out of the wire harness or it wouldn't be a mystery.

A mechanic will start "the chase" by removing fuses at (the three or four) panels to isolate which circuit the wire is on.

If the wire has no voltage or continuity in any fuse configuration - perhaps it was added and removed for some "add-on" that was removed.

I'm sure you've already seen the wire is a particular length. It could only attach to anything within reach of it's length.

-----------------------------
if it were my car i'd say it looks like it had gone to the the little red plastic box between the batter and AC that attaches the battery RED to the rest of the car's red. if i remember - i had a wire there that looked like that which was loose or off and re-attached it. i had been surprised there had been no apparent effect from it not having contact.

 

That's the wire that's for adding 12V for a trailer brake controller. It's taped to the wire harness from the factory. If you voltage test it you'll see that it's no hot. Just tape it back to that wire harness bundle.