I would also try to disconnect, then reconnect the electrical connectors on the BCM located under the passenger seat foot well. They have been known to corrode if moisture is allowed to sit down there and not cleaned up. 
 I would also spray some electrical cleaner on both ends of the connectors, and add some dielectric grease to them. You just don't know if the car was left out in the rain with the top down prior to your purchase. Wet connectors and add time can lead to corrosion.
How long have you owned the car? And what area are you in? We have a pretty national Solstice/Sky group so someone may be in your area willing to help.