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You must clear all the codes. No tools needed. At the top of this page on the Red bar click "Other", then "Tech Tips", then "C5", then search down the list till you find "Erasing DTC Codes" and it will tell you exactly what you need to know.
You will probably find some codes set. The ones with "H" behind them are nothing to get worried about. Codes ending in a "C" you will need to do something with.