What is "TPMS"? TPMS stands for "Tire Pressure Monitoring System". TPMS is a warning system indicating to the driver when a tire is significantly under-inflated. Beginning in September 2007, all new light duty vehicles sold in the U.S. are mandated to be equipped with TPMS. Most people ignore their tires, yet tires are undoubtedly a critical safety component. A tire can lose up to half of its pressure without appearing to be underinflated. The small battery operated sensors are located inside of the tire to prevent drivers operating their vehicle with unsafe low tire pressure.