Visit this site http://www.totalcardiagnostics.com/toad for more information on OBD2. Let's look at the OBD2 Scanner tool first, since we sell low cost OBD-II scan tools. It will probably be the only thing you will need to buy to do your own diagnostics and clear your trouble codes, which turns off the check engine light. We have found that all of the above packages are free downloads that work with our OBD2 Scanner tool.