It pissed me off today, so I started looking for a solution. My wife ended up finding it on a Heritage forum. The trick was getting into the service menu. With the car in park, or in drive or accessory mode; hold the physical Home button and while holding it press the tune button twice as a double click.
There is a camera option and you can turn those lines back on. You can run diagnostics on the speakers/volume (be careful as they use the speakers at full volume), you can test the microphone levels and see a bunch of other information about the electronics. The best thing is that you can see the battery voltage when the car is running, if you enter the menu with the engine running. If you do it in accessory mode, you can see the quiet battery voltage.
I hope this helps.
