This was something that was added to the software in the truck and if you ever go to the dealer and they reflash your ECM you will get this back-up-door-open alarm. They might be required to do it. I know a guy that had it done to his truck and he used a Dodge DRB computer to try to find it in the program and disable it and he couldn't do it. It is non-reversable at this point. I have heard of some guys putting in a switch to turn off the horn while backing but other than that I don't think you have a choice