The audio system has a self diagnosis feature, that is accessed differently than you describe. If you go to www.infinitiservicemanual.com
and navigate to the 2013 G37, then open the link for the AV section, you can see it starting at page AV-94. Hopefully getting in to this mode, and then exiting it will fix whatever it's doing. If that doesn't work, you might try disconnecting the car's battery overnight to see if it resets something.