Certain vehicles may have been assembled with a transmission range sensor (TRS) that was calibrated out of specification for reverse gear. If this condition exists, the transmission may not properly engage reverse gear and/or if reverse gear does engage, the "R" indicator on the dash or the backup lamps may not illuminate. These conditions increase the risk of a crash or a pedestrian being struck due to the vehicle's not signaling it is in reverse. Dealers will inspect and replace the transmission range sensor as necessary to correct this concern. The Ford recall number is 12C23.
Resources for the Repair and Maintenance of your 2012 Ford Mustang
2012 Ford Mustang
2012 Ford Mustang Recalls (Recent)
2012 Ford Mustang Reviews
I rated reliability for the 2012 V6 Convertible only 3-stars simply because I've only owned it for a few weeks so it's too early to tell. I did want to report on two issues. 1) The V6 model doesn't come with a spare tire - the first car I've owned that didn't have one. According to Ford's web site: "Neither a full-sized nor a mini-spare tire is available from production as an option." And, 2) Water leaks into the trunk. Being repaired as I type this - according to a Google search this problem plagued Mustang convertibles in previous model years as well. :-(