Think you may need the service manual for this one, but try a memory reset:
Locate the microprocessor, usually on the control panel pc board. There should be a large value capacitor or a battery on this board. sometimes it's on the main board. If it's a cap (4.7 Farad or something huge like that) with the power cord unplugged, short the cap for 1 minute, then plug the cord in and try it. If it's a battery (silver disc type) remove it by desoldering it, then reinstall it.
If this doesn't work, get the manual. You need to locate the reset line to the microprocessor. With the unit powered up, short the reset line to ground for 5 seconds, then check the tuning again. If this doesn't work it has to be a hard wired option. When you order the manual, make sure to ask for any technical bulletins on that model. They are available, you just have to know to ask for them. Get it from Sony DAPC
http://servicesales.sel.sony.com/web/index.jsp
You may want to call them to ask about the bulletins.