Hi, my 99 side markers & tail lights (everything that's that's supposed to light up on the butt when you have your headlights on) are not working, everything else does and all the fuses light up except for my "running light" fuse which I've replaced with a new one already. The (running light relay) fuse was missing when I bought it and I placed a new one there and it lights up too. I've swapped with tail light harness and bulbs on side markers as well, still nothing. Every other fuse lights up, I tested them all. Can provide any pictures necessary. Horn also does not work if that matters

 

Update* noticed this button on my console to the left of the steering wheel and traced where it went. Nothing happens when I push it and nothing changes when I disconnect it, maybe this is what's wing with my lights? Anyone know what this might be for?

 

Still don't have power to the running light fuse at all, to-or-from but i resolved my tail lights issue, it was fuse 35 had blown, the License light fuse on the diagram. It seems my strange wire had nothing to do with it, but if anyone knows what the button/wire might do or be connected to, please let me know because i Hate unnecessary wires.

 

That looks like its from the car alarm. Its used to defuse the Alarm if its going off and your remote doesn't work or is dead or missing and that button is also used to program the car alarm remotes. Maybe the car had a aftermarket Alarm that may have been removed.