I'm looking at adding turn signals to my mirrors on a 2015 SCrew. Why? Too cheap to spend big $$ to buy them. So, my main question is if there is existing wiring to tap into or do I need to run a wires to the mirror from someplace?? Thanks!

 

If you take that triangular piece of trim off the "A" pillar, you can access the connector. See if it's an 8 pin with all sockets filled.
Right now, I'm still waiting for my TT mirrors, but, I just might have the small mirrors up for sale, that have the turn, and I've got an adapter to give you running lights too.
Shoot me a PM if you might be interested.

 

My aftermarket tow mirrors gave me turn signals on the Boost mirrors (new), heated main mirrors (have rear defroster). 8 pin, plug and play.