How do tire sensors work in modern autos?

when the temperature changes the tire pressure changes and wheel Sensor pick up on the change and will notify the computer of the change if you have just air in the tire. but if you don't wont the light to come on every time the temp. changes. thy now have been taking out the air and installing nitrogen which the temp. does not effect.

In colder weather, the pressure drops. Also, tires lose about 2psi/month, rubber lets the air bleed thru. Get a gage and check/fill your tires. You can't tell just by looking at them. That's why they started using the pressure monitoring systems.