Thanks again! I've found this site extremely helpful. I had found a jpeg of the pinout of the radio/CD connectors, but in German. After doing a little translation, it became obvious the connector you mentioned is the intercom connection. Continuing, I disassembled the radio and found considerable corrosion around the PC board that the connecter is on and a half a dozen components in the vicinity. I cleaned up everything the best I could with component cleaner, and reassembled, making sure all the connectors were seated. No change, same symptoms.
At this point, my assumption is that there is a failed component in the radio. I also noticed that the CD eject button doesn’t seem to work either. I read a posting from another that Becker will rebuild the unit for $400. I call them Monday to inquire about that.
As an aside, in my case, the boot that the radio sits in had collected noticeable water after I washed the bike. That boot doesn’t have any kind of drain and the radio is not water tight, so it does not seem surprising that many people have radio problems after exposure to water. On examining the radio during disassembly, it is pretty well constructed, but no radio is going to survive sitting in a bath of water…