You hop into the car, ready to head out and notice a new light shining brightly on your dashboard, the tire pressure indicator light. Being conscientious and concerned about safety, you stop at the nearest gas station, ensure all your tires are filled to the right pressure and hop back into the car -- only to notice that that tire pressure light is still on. You assume the pressure gauge was probably off, recheck the tires at another gas station, but the reading is the same. Every tire appears to be filled to the right pressure.
What could be the problem?