What is a TPMS Sensor?

TPMS? What's it all about?

TPMS stands for Tire Pressure Monitoring System. In other words, TPMS is a sensor that measures the air pressure in your tires. In fact, TPMS consists of a valve and a sensor. Not all TPMS systems are created equal. TPMS sensors monitor the vehicle's tire pressure in real time. They tell the driver if the pressure is adequate or if it is adversely affecting vehicle control, driver and passenger safety, and fuel economy.

Insufficient tire pressure, or even a discrepancy in tire pressure levels, has a significant impact on driver comfort and vehicle behavior in difficult situations (such as hard braking or maneuvering). Too low tire pressure increases fuel consumption. Conversely, if the pressure is too high, passenger comfort is compromised. In general, tires that are underinflated or overinflated wear out faster.

Drivers generally do not feel or see the difference in tire pressure because it is invisible to the naked eye. What's more, with low-profile tires, it's easy to overlook even a 1-bar pressure difference. In addition, uneven surfaces make it impossible to gauge tire pressure at a glance. Few drivers are in the habit of checking their tires regularly.

That is why vehicles are now equipped with tire pressure sensors. In a TPMS system, sensors monitor either tire pressure or pressure differential in real time. The driver receives real-time tire pressure status information.

How do TPMS sensors work?

TPMS pressure sensors installed on passenger vehicles fall into two categories:

• Indirect TPMS pressure sensors
• Direct TPMS pressure sensors

A direct TPMS system is a device typically installed on tires near the valves. It consists of the following components

• Pressure sensors
• Radio transmitters
• an autonomous power supply

These allow the direct TPMS system to send the pressure levels of all tires to the on-board computer and display them on the screen. The synchronization between all the sensors and the on-board computer is extremely precise. This means there's nothing to stop you from changing wheel positions, as long as you reset TPMS direct after each wheel change and then import the new data into the system. These tasks should be performed by a trained professional.

In practice, an indirect TPMS system mimics a TPMS system. Because of the way it works, it is one of the components of the ABS and ESP systems. Don't forget that the indirect TPMS system is much easier for the driver to use.

These sensors send the rotational speed of each wheel to the ABS and ESP systems in real time. The higher the tire pressure, the larger the actual wheel diameter. Conversely, the lower the pressure, the smaller the diameter. The indirect TPMS system accesses this information and counts the number of wheel rotations. If it detects a wheel with an out-of-range speed, it alerts the driver by illuminating the warning light on that tire.

What are the benefits of a tire pressure monitoring system?

TPMS pressure sensors on vehicles offer a number of benefits. Here are just a few:

• The TPMS pressure sensor helps the driver maintain proper tire pressure.
• The TPMS pressure sensor increases driver and passenger safety.
• The tire pressure sensor contributes to driving comfort.
• The TPMS pressure sensor slows tire wear.
• TPMS pressure sensor optimizes stopping distance.
• Tire pressure monitoring significantly reduces fuel consumption.

Why is tire pressure monitoring important?

Tire pressure monitoring helps drivers properly maintain their vehicle's tires, improves vehicle safety and contributes to fuel efficiency. The U.S. National Highway Traffic Safety Administration (NHTSA) estimates that 533 deaths per year are caused by tire failure in traffic crashes. Adding TPMS to all vehicles could prevent 120 of the 533 annual deaths and save up to 8,400 injuries each year. The French road safety organization Sécurité Routière estimates that 9% of all fatal road accidents are due to underinflated tires, and Germany's DEKRA estimates that 41% of personal injury accidents are related to tire problems. Tires naturally leak, and a typical new tire can lose between 3 and 9 psi over the course of a year. With most drivers checking their tires only at service intervals and when problems arise, there are significant opportunities for fuel savings and efficiency.

With this in mind, the U.S. federal government has mandated the use of TPMS. The TPMS required by U.S. law must warn the driver when a tire is underinflated by up to 25%.

How do I know if a vehicle is equipped with TPMS sensors?

To determine if a vehicle is equipped with TPMS sensors, simply turn the ignition key to the ON position. You can be sure your vehicle has a TPMS pressure sensor if the low tire pressure warning light illuminates on the instrument panel.

How do you reset a tire pressure sensor?

The technique for resetting TPMS depends on the make and model of your vehicle. In general, here are the main steps to reset your vehicle's TPMS:

• Inflate the tires to the correct pressure: This can be found in the vehicle's service manual or on the decal on the bottom of the driver's door.
• Press the reset button: Most cars equipped with TPMS have a button on the steering wheel that recalibrates the sensors. Turn on the ignition and press the button for 3 seconds or until the light flashes.
• Drive for 20 minutes: Driving at a steady speed will recalibrate the TPMS sensors in the tires.

In some cases, the tire pressure must be reset using a TPMS electronic reset tool that plugs into the tire valve. If this is the case for your vehicle, you'll need to visit a service center to have it reset.