Having recently been through this with mine here's a few bits I can tell you. I have the Bose system so some bits may differ slightly.
If you're running the cable in to the cd changer port on the back of the head unit it won't do a thing. The system is designed in such a way that it needs to communicate with the changer or something pretending to be one.
Fortunately for me my car came with the changer so I was able to bodge together a setup that 'worked' as you can see here.
As to how well it worked, well that's another matter. It turns out the right channel and ground are swapped (I think) as when I was charging anything connected to it the right channel would stop playing. That wouldn't take too much to sort out. However, the setup does rely on the changer being there to keep the audio path active.
Short of that your choices become very limited. In the end I went for the basic Grom Audio Aux unit (be sure to get the right cable as their vehicle identifier can get it wrong). This is connected in place of the changer and tells the head unit that it's there and 'playing' a disc. Works perfectly well.
Its the original one but think im gona change to aftermarket.
MedicalFlyer thanks for your help, i dont think ive got a cd changer in the car as i only got it a few days again so just finding things out with it, not had a honda before so evrrything is new to me about them and just trying to find out how things work. Thanks for the reply