I have a 2007 Cts 3.6L and the a/c was on, and I noticed the air wasn't coming out very cold like usual, and it was set to 60 degrees on both sides. After a few hours, the A/C Off message kept flashing and the air would still come out, but warmer now that the a/c was shutting itself off. Could this be a refrigerant leak? It's all the original parts, never added any refrigerant. Any suggestions?, oh and the only code I received was P0403 which is Bank 2 sensor, thank you in advance