Ignition Coils Failure problems of the 2009 Cadillac CTS

2009 Cadillac Cts. Consumer writes in regards to vehicle vibration/unexpected loss of power and transmission shifting and acceleration problems. The consumer stated the vehicle began shifting gears erratically, vibrating and lacked power. The condition appeared irregular and for some time, no trouble light appeared. Once a light finally appeared, the vehicle was taken to a Cadillac dealer who determined that all the ignition coils on one side of the engine were defective. The service representative explained that when one or more ignition coils fail, the engine would have a greater vibration and lack of power. In addition, the coil failure would cause the transmission to unexpectedly downshift to compensate for the loss of power and with multiple coil failures it may shift multiple times each time more power was needed to maintain the throttle speed. In July 2013, the consumer began experiencing the same performance issues. Again, no trouble light appeared. A trip to the dealer resulted in nothing being found, despite the service history of the vehicle. The condition continued and in August 2013. The trouble light appeared. The dealer found an ignition coil on the other side of the engine was defective.