There's a device called "steering interface" that you call use to make your original Car steering remote work when you change your stereo head unit. Its made by Skott http://www.skott-audio.com .
I recently bought a Montero sports and it comes with a JVC head unit with OEM steering wheel remote. I plan to change the head unit to Pioneer that's why I learned of this "steering interface" device. My friend gave me this device but I still haven't install my new radio.