Tire Knowledge

Tire Pressure Monitoring Systems

A tire pressure monitoring system (TPMS) is an electronic system designed to monitor the air pressure of a vehicle and display a warning if one or more tires are under or overinflated. TPMS systems were introduced on some models in the mid to late nineties and became standard on all models in September of 2007.

Direct TPMS Systems

Tire Pressure Monitoring SystemsVehicles that incorporate direct TPMS systems utilize individual sensor / transmitters in each tire and wheel assembly. The sensors can be a part of the valve stem assembly or a band mounted sensor that clamps around the wheel. Direct TPMS sensors broadcast tire pressure data to a receiver mounted in the vehicle. Processed TPMS data can be displayed as a warning or on some vehicles actual real-time pressure readings. Direct system sensors incorporate non replaceable batteries that will require replacement once battery life has depleted. Battery life will vary by manufacturer and conditions, but should last several years.

Indirect TPMS Systems

Indirect TPMS systems utilize the vehicles ABS system to detect low tire pressure conditions. As a tire loses air its overall diameter changes and subsequently turns at a higher rate of speed compared to the other tires. Your vehicles wheel speed sensors pick up the difference in rotational speed; this information can be used to send a warning message if certain conditions are met.


Many direct and non direct TPMS systems require a relearn procedure after a tire rotation. This relearn process is necessary with some manufactures to accurately warn the driver that a specific tire has pressure condition of over or underinflation. Some vehicles require special TPMS tools to relearn, reset, or replace sensors.