tire pressure sensor?

If the tire isn't actually underinflated, yes. According to Hyundai, this is a normal condition. I'm not so sure, however. The lamp is set to come on when the tire is about 20% low. Considering the normal variation in temperature in most areas of the United States, and using the ideal gas law to estimate, I'd say the normal pressure variation due to cooling to be about 13%.

The short story is to check your pressures. You probably need to add a few psi to all the tires.

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thanks that's what i did ,even though they all read the same and only one tire showed up. its all good now.