I had this happen when the temperatures started getting cool in the mornings. I checked the pressures and they were all low (~26 psi). I filled them up to 32 in front and 33 in the rear and haven't seen the light come on again.

The pressure sensors are part of the valve stem (on the '04 coupe stock wheels). If the pressure is correct and you still are getting the light, your dealer can plug in to the OBD-II port and determine which one is bad.