Genuine OEM Audi Engine Stop Start Switch, part number 4L0905217. This switch manages the automatic engine stop and start feature, which temporarily shuts off the engine when the vehicle is stationary to improve fuel efficiency and reduce emissions. It is typically located on the center console or dashboard, providing easy access for the driver. Weighs approximately 0.068 kg and features distinct 'ENGINE START' and 'ENGINE STOP' buttons. Selecting a genuine OEM switch ensures precise electronic communication with the engine control unit and durable tactile feedback, maintaining the intended functionality of this advanced system.