I have a Sony CDX-F5500 that was installed in a used car I bought. It has some problems. I can only tune in one direction only. Once you pass the station you want, you have to go all the way around to try and stop on that station. The memory buttons do not work at all. And several other features do not work. About the only thing that does work is the Up tuning and the CD player, but even the CD mode is hard to select. Is there a chip that controls the faceplate functions? Is my problem in the removable faceplate, or is it in the tuning/CD unit? Or should I just trash the unit? Any help is appreciated.