wiring diagram

Suggest picking up a Haynes manual for your vehicle, which will have this. The other option is to take the backup light off, and look at the wire itself -- it should match in color to the one you are seeking. Often times it will be multiple colors -- black with a pink stripe, or something like that. These are usually not shared by different wires so whichever goes to the backup light is the one you want to find under the dash.