2001 Mercedes Benz ML320 check engine light

Check enigne lights can be caused by many failures, some more serious than others. The best way to find out what is causing the light is to have an engine diagnostic scanner put on the vehicle. You should be able to go to any Autozone and have this checked out for free. Get all the code info including the number (i.e. P0300) and the listed info (Low voltage O2 sensor bank 1 sensor 1). You can send me the info through this site or post another comment and one of us will explain the next step to take.