I went to start the car this morning and the battery was too dead to light anything or ring any chimes. Put a jumper on it and it started right up. BUT it had lost trip odometer reading, mileage reading, and the radio asked for CODE. What's going on that so much information was lost?

 

Probably have a bad cell in the battery. You don't say what model or year you have, but since the '90's this kind of stuff is normal to see when you get a really dead battery. Many shops use a tool that keeps current flowing while they change the battery to keep from losing clock and radio settings.

 

How do I reset the code for the radio? I have a 2001 C 70. I will get the battery checked. Thanks.

 

The code is unique to each radio. Assuming it is the original radio that came from the factory your local dealer should be able to retrieve the code for you using the car VIN. Assume that they will require proof of ownership before handing it over.