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Tire Pressure Monitoring System – what is it? and how does it work?

The use of the Tire pressure monitoring system started in the year 2008. Every model car designed that year features their very own Tire pressure monitoring system. Because of its success in keeping roads safer, the law recommended the system to all vehicles.

Note: The system is not only great for safety. Fuel economy is another perk to enjoy.

What is TPMS?

TPMS front side
Credit: commons.wikimedia.org
TPMS back side
Credit: commons.wikimedia.org

A Tire pressure monitoring system is an electrical unit designed to monitor air pressure within a vehicle’s tire. This is possible with the help of sensors. They give a real-time record of the air pressure within tires.

How does the TPMS work?

When in use and the pressure within the tire reduces the TPMS indicator will light up. This means the tire is detecting low or high air pressure within a tire. The indicator is located on the car’s multi-information display. It’s not hard to miss.

Direct vs. Indirect TPMS

There are two types of TPMS. The difference between them is how they measure air-pressure within a tire. The types of TPMS includes:

  • Direct TPMS
  • Indirect TPMS

InDirect TPMS

This type of TPMS makes use of a tire’s external properties to measure its air pressure. It is the standard for European countries and it can be found within the speed sensors and the braking system.

There are two generations of the Indirect TPMS named:

  • First generation indirect TPMS
  • Second generation indirect TPMS

All are classified based on how air pressure is measured.

First generation indirect TPMS: The first generation TPMS adopts a working principle that measures air pressure within a tire. That principle allows the system to detect under-inflated tires through detecting small changes in their diameter. But it is only for one tire at a time.

Note: The difference in diameter size is measurable with the help of speed sensors of ABS or ESC systems.

Second generation indirect TPMS: this generation of TPMS also detects small changes in the diameter of an under-inflated tire. The difference from the first one is the ability to detect all tires of a vehicle at once.

Note: The second generation TPMS ability to detect low air pressure in all tires at once is due to the software in use. The software is capable of handling advanced processing techniques with the aid of spectrum analysis to measure each tire.

Direct TPMS

The Structure of direct TPMS
Credit: www.researchgate.net

This type of TPMS makes use of pressure sensor installed in the tires to measure air pressure in tires. Because of the pressure sensor location, It gives accurate air readings compared to the indirect TPMS.

Newer versions of the TPMS system can also measure the temperature in a tire. This can give a much accurate reading of air pressure in tires. As temperature do have an effect on tire air pressure.

How does temperature affect tire air pressure

Internal air temperature within tires has a significant effect on vehicles tire air pressure. Heavy-duty vehicles to be specific.

Heavy-duty vehicles tend to have its air pressure a little below, above or exactly 2 bar. This occurs on a sunny day. The perfect time for air temperature in tires to increase. The 2 bar of pressure mentioned is actually above the standards. So, as the air temperature in the tire increases the air pressure within will follow suit.

During the winter, the pressure of the tire will be lower than the standard settings. It would linger around 1 bar of air pressure.

Note: As you notice, the temperature does have a significant effect on the temperature. Which is why both pressure and temperature should be measured, in order to get an accurate and reliable assessment of the air pressure within the tires.

Components of a direct TPMS sensor

 The direct TPMS sensor consists of components, both internal and external. Once assembled, it should be placed or fixed to the valve stem of the tire.

Components include:

  • Pressure sensor
  • Oscillator
  • Radio frequency transmitter
  • Low frequency receiver
  • Voltage regulator
  • Analog to digital converter
  • Microcontroller
  • System controller

Benefits of TPMS

The function of a Tire pressure monitoring system is self-explanatory. It notifies the driver of a vehicle about change in the air pressure within the tires.

Given that being its function, the TPMS unit provides the driver with lots of advantage on the road.


  • TPMS cautions a driver about possible flat tires
  • Enables proper maintenance of air pressure in tires
  • Reduces tire wear and tear
  • Ensures reduction of braking distances which makes for better fuel economy

How to reset TPMS?

If your tire pressure sensor isn’t working properly there are several ways of fixing it. Here are steps to follow that will get your vehicle’s TPMS in proper working conditions.

1. Identify the type of TPMS your Vehicle is Using

This should be the first action to take when resetting your vehicles TPMS. You have to know what type of TPMS your vehicle is using, as It could be Direct or Indirect. They both have their own unique way of being reset.

1.1 How to reset a Direct TPMS

If your vehicle makes use of direct TPMS, resetting the pressure sensors will require a push of a knob on the dashboard. This knob is known as a ‘reset knob’.

1.2 How to reset an Indirect TPMS

If your vehicle uses an indirect TPMS, a tool will be required to reset the pressure sensors. This tool is either a scanning tool or magnet.

Note: If you can’t determine your vehicle’s TPMS, it’s advisable to consult an auto expert.

2. Inflate your tires

After completing the first step your tires have to be inflated. The reason is to ensure there is accurate calibration of the tire’s air pressure. After all the pressure sensors are on ‘zero’.

If the tires are not properly inflated the air pressure readings will be inaccurate.

3. Monitor the battery

If your vehicle’s TPMS makes use of a battery to power up the pressure sensors, make sure it is fully charged.

4. ReAdjust the transponder

This part is located in your vehicle’s tire TPMS. When replacing your tire or after resetting the TPMS, it is best to readjust the transponders till it’s fitted well.

5. Make use of magnet

This is one of the effective ways to reset a TPMS.

What to do:

  • Push down both buttons that says lock and unlock simultaneously on the key fob
  • Make sure the key is on and the is engine off. Then place a magnet over the all valve stems
  • Do it until the horn chirp for each tire in the order left front, tight front, right rear and left rear

6. Use the scanning tool

This is another way of resetting a vehicle’s TPMS. It doesn’t require removing any pressure sensors. Instead, it involves using an OBD2 scanning tool to relearn and reprogram the TPMS sensors.

Frequently Asked Questions

 Q: Can TPMS sensors report their battery status?

A: it depends solely on the model of TPMS in use. There are certain models capable of sending signals in order to indicate battery status. But it only sends the signal after the battery depletes to a certain level.

In the end, a battery report isn’t that necessary, as their battery lives are known to last longer. The reason why the battery life drops too quickly is due to the road hazards.

Q: is it possible to turn off TPMS?

A: No, it is not possible to turn off the TPMS of a vehicle, as it is mandated by a law passed by Congress called the ‘tread’ law.

Q: can the TPMS sensors fit on all wheels?

A: Most tires are able to fit a TPMS sensor. Some tires are not compatible with the TPMS sensor. The way they are placed in the tire’s valves stems holes would cause the motion detection component to malfunction.

Go get one…

 So there you have it…now you know all the basics about the TPMS. its definition, working principle, and reasons why it is needed.

If you don’t have one, get your car a Tire pressure monitoring system. It would make you and the world a much safer place.

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