I am trying to install a Yada reverse camera. It says to tap the two wires going to the reverse light. I discovered, as you will already have guessed, that my 2012 Titan has two black wires (one centered, one to the side), not one, plus the white wire. So, which black wire should I tap? (I want the camera to be on only when the truck is in reverse.) THANKS in advance for your assistance!