One problem related to automatic transmission control module has been reported for the 2009 Cadillac CTS. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2009 Cadillac CTS based on all problems reported for the 2009 CTS.
When driving a 2009 Cadillac Cts the car generates a drone, boom and vibration. This happens when accelerating to or driving at highway speeds. I bought the car new and there has been a problem has been with this car since I took delivery from the Cadillac dealer. Gm has issued a service bulletin (#08-07-30-044b) to install rubber insulators and reprogram the transmission control module. This "fix" did not help. It only moved the onset of the vibration to a higher rpm/speed. When the vibration occurs the car does not feel safe. I am not sure if a mechanical component is going to fail. The drone is constant, distracting and annoying while driving. There is also a boom noise at 5 mph when coming to a stop. This is not a smooth quiet safe car. The Cadillac service mgr says he does not hear anything. I do not agree. Cadillac also says the noises are inherent in the vehicle and have no fix. They are making no attempt to fix the car at this time.