I have a light on that the local chevron says is a 420 code? I called the dealer and he says it may be the catalytic converter and that there is some kind of a flush that helps in most cases.. Then I hear from another engine savvy person, that you don't flush catalytic converters?? They thought it has something to do with the Exhaust system.. I have no warranty so am looking to trouble shoot before the dealer has too! I just received the airbag recall, that they now have the parts- so I will have them check it then also?