We had that happen with both front blinkers. The fast-flash is a warning to the driver that a bulb went bad. I just replaced the bulbs and haven't had a problem since -- which surprised the dealership when I told them about it. They were ready to replace the blinker sockets. I just got bulbs at Pep Boys, not any expensive glass-socket items. I'm kinda watching it to see if it happens again before the 50k warranty runs out.