WHILE OUT SHOPPING WITH MY CHILDREN WHEN I ATTEMPTED TO TURN OFF THE VEHICLE TO DEPART FOR THE MALL, THE IGNITION TURNED TO THE OFF POSITION, I REMOVED THE KEY BUT THE CAR REMAINED ON. I THEN NOTICED THAT THE CHECK ENGINE LIGHT ILLUMINATED. SHORTLY AFTER, THE CAR BEGAN SHAKING VIOLENTLY; I ASSUME AS IT WAS ATTEMPTING TO SHUT OFF. I INSERTED THE KEY, SHIFTED INTO TO REVERSE, PULLED OUT OF SPOT AND THEN BACK IN AGAIN. PROCEEDED TO TURN VEHICLE OFF AND AGAIN, KEY REMOVED BUT CAR STILL RUNNING. AGAIN THE VIOLENT SHAKING ALONG WITH LOUD NOISES BEGAN. AFRAID, I INSTRUCTED MY CHILDREN TO LEAVE THE VEHICLE. WE GOT A COMFORTABLE DISTANCE FROM THE VEHICLE AND CONTINUED TO WATCH. IT TOOK 25 MINUTES FOR THE CAR TO SHUT TOTALLY DOWN. WHEN I WENT BACK TO THE CAR, AS I OPENED THE DOOR, I NOTICED THE WARNING SOUND AS IF THE KEY WAS IN THE IGNITION AND ALSO ALTHOUGH THE ENTIRE DASH WAS OFF, THE CHECK ENGINE LIGHT WAS STILL ON, (IM NOT SURE HOW SINCE THE CAR WAS "OFF" AND NO KEY INSERTED). I DROVE THE CAR HOME AND THE SAME THING HAPPENED WHEN EXITING THE VEHICLE. THE CAR REMAINED ON, BEGAN SHAKING AND THE CHECK ENGINE LIGHT ALSO STAYED ON AFTER THE CAR WAS TOTALLY SHUT DOWN. VERY SCARY EXPERIENCE. I NOTICED VIA THE INTERNET THAT THIS WAS NOT A NEW ISSUE. I WONDER WHY GM WOULD NOT HAVE CORRECTED THIS PROBLEM WITH ITS VEHICLES BY NOW. I AM A SINGLE PARENT AND MY TEENAGE DAUGHTER SOMETIMES HAS TO RUN ERRANDS FOR ME IN THIS VEHICLE, I WOULD HATE FOR THIS TO HAPPEN WHEN IM NOT WITH HER.... ITS WAS FRIGHTENING ENOUGH FOR ME! *TR