I wanted to make the footwell lights come on whenever my headlights come on but I don't know how to wire it so can anyone help me? Perhaps a wiring diagram would be very helpful as well. This is for the 2012 TSX Special Edition
This is should be an easy modification so you dont really need a wiring diagram. All you have to do is find a wire near the steering column that gets 12v only when the headlights/parking lights come on. Tap into it then run a wire to the harness of the footwell lights.
Its pretty simple.
The following is for the 09-10 tsx but should be the same for the 11/12. Just make sure you test with a multimeter.