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First thing double check the gas cap, make sure it is not loose, if it is loose you will need to drive around for awhile for the light to go off. There could be many, many reasons why the light went off. The best way to tell what is going on is to ask your vehicles computer what it is having a problem with, this will require a scan tool to pull codes. Once a code is found it will give you or the technician an idea of what is going on. Some Auto Zone's will pull codes for you at no charge, this being a new vehicle with only 900 miles I would take it to the dealer because any repairs or costs to you should be covered under warranty.
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