What Is TPMS and How Does It Work?

TPMS stands for Tire Pressure Monitoring System, an electronic system that monitors the air pressure in a vehicle’s tire. There are two types of TPMS, direct and indirect. Direct TPMS measures tire pressure through a valve-mounted sensor located in each tire, while indirect TPMS uses the ABS system to signal air pressure loss.  

How Does TPMS Work?

Both direct and indirect warning systems notify drivers about the changes in the air pressure of one or more tires. With both direct and indirect TPMS, if a tire is detected to be underinflated by 20% or more, a warning light illuminates on your dashboard. Although they have the same goal, the two types of TPMS work differently - it is important to understand the difference.  

As the name suggests, indirect TPMS approximates tire pressure “indirectly” by using data from the vehicle's antilock brake system (ABS). One of the biggest downsides of indirect TPMS systems is that they do not display the actual pressure value of each tire. Also, depending on the vehicle, the warning light will appear when it detects low pressure, but will not display which tire is low - it needs to be manually checked.  

Direct TPMS readings are provided by pressure sensors mounted inside of each tire that send pressure readings to the vehicle’s central computer (ECU) which are later displayed on the dashboard. A warning indicator light on the instrument panel and an audible warning notify the driver if a 20% drop in pressure occurs. With direct TPMS, drivers are alerted sooner, and if the car is equipped with pressure by location display, it will show readings for each individual tire.  

A TPM system is a safety feature that helps drivers to always keep their tires properly inflated. A direct TPMS offers more accurate pressure readings compared to an indirect one. On a shop level, learning the difference between the systems helps to offer the best solution for your customers and provide the best service. 

We would love to hear from you if the vehicles you service are equipped with Direct TPMS or not? What about your personal vehicle?