I just picked up a 2000 E39 M5 last week. The previous owner put a Mk IV widescreen nav system in it a while ago. He used the nav on the way to get a new battery the weekend just before I got it and everything worked fine including audio instructions. The unit has a ICE-link iPod interface that works fine, as does the FM tuner.

When I got around to try programming a destination this past weekend, I found that I get the map instructions fine, but I get no audio from the nav. If I have the radio or iPod playing, the audio goes down in level for a few seconds as I approach an indicated turn, but there is no audio instructions from the nav unit.

I've tried setting the nav volume (in the settings menu) all the way up and there is no effect.

The only clue is that the audio was there before the battery was replaced and now everything is OK except the nav audio is missing.

Any ideas where to look? Am I missing a setting somewhere?