Brake Controller and 7 Pin Installation on 2017 Tacoma Questions

I am trying to install both a 7 pin connector and a trailer brake controller on my 2017 Tacoma. I already have 4 pin wiring in place. It is my understanding that since my truck is not prewired I’ll need to hard wire the brake controller and run the wires myself. My only question is which wire should I tap into for the stop light switch. I found a connector behind the brake pedal with 4 wires.

 

Your post was in October so this may no longer be relevant for you. Do you still need this information? I'm going to do the same installation you are doing soon and I believe I have figured out a process that will work, correctly identifying the wire without damage while standing on my head under the steering wheel.