This tool is one of the best I have seen and used.  It is so user friendly and even tells you righ in the scanner what the code number is and what the code means.  This item is priceless!  If you own a car you need to own one of these.  I have an Audi TT, which made me skeptical that this tool would do an accurate job of reading the diagnostic codes.  The other reviews I read were all about domestic made vehicles.  But; no problems whatsoever!  it read the codes and erased them easily.  You can also check different sensors throughout the engine to make sure they are working properly.  This tool diagnosed my faulty air mass meter with a P0172 code = System to rich.