So I drove the car to work yesterday and when I went to drive home I had two warning lights: low tire pressure and flat tire warning. The tire profiles looked good, no sagging sidewall. It was around 40 degrees and the pressures were at 27 rear and 26/27 front. When I checked the message center it said -4 below tire pressure. After driving home the pressures were back to 29 rear and 27 front(default) but the warning lights haven't gone out even after restarting the car several times. Am I missing something really simple?

 

Those tire pressures seem really low to me, especially since those are post-driving. Are those within the recommended psi range?

 

Yup, too low...30front/31rear is acceptable cold tire pressure
I might have a bad sensor?

 

Make sure you check the pressure in the TPM sub menu, and not the quick check in the main menu. It has been my experience that once the sensor triggers it does not go off until you add the required amount of air. It will tell you how many psi you need to adjust.