How Does TPMS Work?

By Greg Iorfida

A Tire Pressure Monitoring System (TPMS) works by routinely checking tire pressure levels in all tires that are installed on a vehicle. The type of TPMS (Direct TPMS or Indirect TPMS) determines the mechanics of how tire pressure levels are monitored.

With an Indirect TPMS, all tire pressure monitoring data is estimated, using the ABS (Anti-Lock Brake System) to approximate tire pressure. This is a disadvantage, as an Indirect TPMS often fails to provide accurate tire pressure information, when it is needed most. Ironically, the proper functioning of an Indirect TPMS is largely dependent on the monitored vehicle’s tires already being properly inflated, which essentially defeats the purpose of a TPMS. What’s more, since an Indirect TPMS is unable to read tire pressure status on a tire-by-tire basis, the system may fail to warn drivers when all four tires are equally under-inflated or equally overinflated.

Alternately, a Direct TPMS provides highly accurate tire pressure monitoring results, using tire pressure sensors that are mounted on each wheel of a vehicle. The tire pressure sensors used by a Direct TPMS collect tire pressure data from the tire valves on each tire, reporting tire pressure information in near real-time.

Direct tire pressure monitoring systems are preferred by consumers for their reliability and for their convenience, as Indirect TPMS requires manual resets of the system by the driver, when triggered. What’s more, car owners with an Indirect TPMS must also manually recalibrate the system whenever they add air to the tires in their vehicle. For these reasons, Direct TPMS is the most popular type of tire monitoring solution on the marketplace today.

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