On my cars the onboard 'computer' is taught to recognise the fob: there is no change to the fob's output.
Again on mine, you short a wire in the boot to ground and then have so many seconds to set the fob's code into the car. If you only have one fob, you just do it twice.
There are..or were, loads of fobs for sale on e-bay. Mine would have cost $200 with programming, but I paid $21 to a NY company who put a crib-sheet in the box.
Do you not have a Honda [thread SERPI] forum? I'm on the Caddy one for everything I need to know. Fantastic info.