03 Tacoma battery dies after sitting for 3 or 4 days

Do you have a scan gauge or other obd 2 hooked up all the time?

 

If it's a factory installed hitch and wiring then the fuses are located under the back seat. If it's not factory installed then who knows where they are

 

I do not have a scan guage hooked up all the time. I can tell you that the hitch and lights are not factory installed because when I took the carpet and seats out to clean nothing was under there, the only wires under it behind the seat is for my emergency lights and my CB antenna.