The "TPMS" light illuminated. The low tire pressure light did not come on, however. I called my local Kia dealership and they said to bring the car in. They hooked the car up to their computer and said that one of the tire pressure wheel sensors had failed. They said that on these newer cars with tire pressure sensors mounted inside the wheel, it's common that tire shops accidentally cut the sensors off when removing tires from their rims. If this had been the case, the sensors are $200 EACH (there is 1 in each wheel) and it would have come out of my pocket. Thankfully, this was not the case. The sensor was simply faulty. Since my Optima was still under warranty, they replaced it free of charge. It only took them about 30min. while I waited. The "TPMS" warning light is no longer illuminated. I'm happy not to have it starring in my face anymore.

Should one of these wheel sensors go bad, the car is perfectly safe to drive. Your tire pressure monitoring system won't notify you of low tire pressure is all. No biggie, but an expensive problem for something rather insignificant.