I'll bet it is the switch on the dash. They are known to go out. I would order a spare to have on hand. In the mean time, pull the dash panel, unplug it, plug it back in and it will likely work fine. Mine acted up at 37k miles and has been fine for the last 9k miles. I don't believe that is covered under the power train warranty, but it is under the bumper to bumper warranty.