OP said he want to change door lock "code" so that would not be the "black box" controller the above posts are showing. The key FOB controller is different from the door keypad controller.
Do you have the Grab Handle style with the built-in keypad?
If so, the controller is built into the handle. You need to access the wiring (there would be a removable panel on the inside of coach) and there will be a single wire (yellow) that is not connected to anything that needs to be grounded - or the factory could have installed a momentary push button to connect the yellow to ground). That wire needs to be grounded to put the keypad in program mode.
If you don't have the Grab Handle style - forget what I said above