TPMS is an abbreviation for "tire pressure monitoring system," a system that monitors a tire's internal air pressure electronically. A TPMS is available in direct and indirect variants.
A direct TPMS uses a sensor inside the tire's assembly and communicates with the car's computer system directly. This type of system generates a warning if the pressure of a tire drops below 25 percent of the manufacturer's default pressure level.
An indirect TPMS system uses a vehicle's anti-lock braking system to measure the diameter in each tire. If there are any problems with the vehicle's tire pressure, it causes the "low tire pressure" warning light on the dashboard to flash.