This weekend, my 2008 grand prix just started giving me both the yellow light by the dash and the message that the low tire warning system has been activated message. I checked all my tires and none of them have a leak or are even low. My left front tire is the only tire not showing a psi reading on the HUD though so I know its an issue with that tire. Does anyone know how to fix or how much it costs to fix the sensor in that tire as I am assuming thats the problem?