Bill I would "assume" that a code is required but the fact that you have other functions makes me think maybe not? My '95 E320 requires a code like when the battery is disconnected (or goes dead blush ) but at that point nothing functions until you put in the code. I think with your VIN and a call to your local RAM dealer they can tell you if it needs a code and what your code is. On the other hand I wonder if the lack of audio is the reason for the replacement radio??

Mike