I took off my seat when installing my undertail today and noticed there was a wire harness with a green and brown wire going to it, the harness wasn't hooked up to anything, curious what it is because I want to use it to hook up a led license plate light but not sure if it should be hooked up to anything else, thanks!

 

i think thats the ground.

 

It sounds like the service connector.
Jump the two wires and the FI light will flash codes.

Not my pic, found on Google.

 

For plate light I tapped into the running lights in the back tail. Multimeters are your friend.

 

+1

I'll add to that soldering irons and electrical tape.