On 3/15/2017 around 8am, i started my car to leave for work and the car showed a warning "check hybrid system" and the corresponding warning light came on. the gasoline engine also started right away and stayed on, even though the ev battery was full. the engine remained on throughout my commute to work and back to home in the evening. i plugged the car in my garage for charging overnight with the timer set to start the charging at 10pm. around 10:45pm, my wife and i opened the internal garage door from inside the house and immediately smelled exhaust fumes and heard the engine running. i opened the garage overhead door right away and unplugged the charging cable which turned the engine off. just to be sure, i plugged the cable in again and turned off the timer to restart the charging immediately. as soon as the charging started, the engine came on and after a few seconds started revving up also. i immediately unplugged the charging cable and engine stopped. i took the car to the dealer today and am waiting to hear back from the dealer. i think this is a potentially serious safety issue and hence i am reporting it.