Well first, welcome to the forum, since I see this is your first post! I would be thinking coolant temp sensor as well for the next thing to try, but if you have any warranty on it, I would take it in and let them diagnose it. Could be the temp sensor, could be the gauge, could be a couple things and nothing worse than throwing money into parts that aren't the problem. As for resetting the code, you can try the "key dance" method, clicking the key rapidly from "off" to "on" several times WITHOUT starting the vehicle and see if that doesn't do it. How is your coolant level BTW?
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