Displays a warning on the instrument panel if one or more tires are under- or over-inflated. The warning will come on if one tire goes flat, but will also come on if, for instance, cold weather has caused the pressure in all tires to drop below safe limits. Some are more specific about which tire(s) are affected and by how much, but having some sort of tire-pressure monitor has been federally mandated on new cars since the 2008 model year.
