I have done this on a couple of radios. The MP3s act differently than the others and the layout is slightly different. On my MP3, the radio stations and sound settings are lost after the car is off for a little bit just as a previous poster stated. I am going to solder the pin back on and find a dealer and stop this. Note, the rest of my post deals with the eeprom soldered to the board in normal status: I noticed that when the car is in ACC, the radio functions perfectly and when the car is put into on, the radio locks after the signal from the class 2. However, what is actually telling the radio to communicate with class 2 at the moment the car is turned on? The reason I ask this is because if I unplug the class 2 and then turn the car to "on" right away, I can see the radio lock before the 10 seconds end and the screen turns off...however, if I have the key in ACC, I can pull the class 2 and the radio will go off in 10 seconds without locking....therefore, something is telling the radio to look at the class 2 and lock if the information does not match or if there is no information at all. I grounded out the class 2 with my multimeter and watched the voltage signals, when the car goes on, it spikes to 3V for a second and then keeps transmitting its serial data that shows up in varying voltages bouncing around from .1 to .4V.
I hope I am being clear.. =\
I know the radio gets its information through the data bus from the bcm, but the act of the radio locking when the data bus is unplugged and the car is turned on does tell me that another signal is being transmitted somewhere to the radio somehow... I grounded out all of my other wires with the multimeter and saw no changes from ACC to ON for any of them so I don't know what is changing in order to tell the radio "check out the data bus now to see if you're not stolen!" =P
Yeah, anyway.. You guys get the jist of it. If we can somehow figure out and stop this change going to the radio when the car is switched on from ACC, then we don't have to worry about anything. The radio will retain all of the information and we won't see any calibration signals. At least for me.... I don't see any calibration or anything as long as I keep using ACC (with the eeprom still connected, that is).