TPMS, or Tyre Pressure Monitoring System, is an electronic safety system that monitors tyre pressure and alerts you when one or more tyres are underinflated. It can work via the tire-mounted pressure sensors or the car's ABS wheel-speed sensors, which estimate a tyre's pressure loss.
The most common TPMS warning is a yellow tyre-shaped icon with an exclamation point that appears on the car's dashboard. Although TPMS detects pressure loss at an early stage, it does not constitute a tyre pressure check by yourself with a meter at the pressure level stated by your car manufacturer.
What is TPMS in a car?
A TPMS basically keeps track of each wheel's air pressure level inside the tyre. When tyre pressure reaches levels that endanger driving safety, the driver receives a driver's alert.
Having no TPMS can easily lead a car driver to be caught with under-inflated tyres and to drive with tyres in a dangerous condition that can lead to accidents. Under-inflation of tyres might cause more heat to be generated, less efficient fuel use, poorer braking or turning, etc., and faster tyre wear. If ignored, an under-inflated tyre can eventually lead to a blowout or loss of control, and any resulting accident would typically be handled under your car insurance own-damage and third-party car insurance components, depending on whether your vehicle, another person, or another vehicle is affected.
The U.S. National Highway Traffic Safety Administration says a TPMS is a driver-warning device that indicates when a tyre is severely underinflated.
On the car dashboard, the TPMS indicator is an alert usually in the shape of a tyre with a slash mark and an exclamation point. In some cars, the tyre pressures are even shown numerically, 32 psi or 34 psi, on the driver's panel instrument display.
How does TPMS work?
A TPMS can read pressure in different ways, depending on the type you select: direct measurement or inductive estimation.
A direct tyre pressure monitoring system uses pressure sensors mounted on the wheels to measure pressure. An indirect tyre pressure monitoring system calculates the pressure drop based on wheel-rotation data collected by the ABS system.
| Type of TPMS | How it works | What the driver sees | Main limitation |
|---|---|---|---|
| Direct TPMS | A pressure sensor fitted inside each wheel or on the valve stem measures tyre pressure and sends data to the car's receiver. | The system may show actual pressure values for each tyre, depending on the vehicle. | Wheel sensors have sealed batteries and can need replacement when a sensor fails. |
| Indirect TPMS | The system uses ABS wheel-speed sensors to detect whether a tyre is rotating differently because of pressure loss. | The system usually shows a warning light rather than exact pressure for each tyre. | It must be reset after tyre inflation, tyre rotation, or tyre replacement if the vehicle manual requires it. |
What happens in a direct TPMS?
A direct Tire Pressure Monitoring System consists of three primary parts: pressure sensors in each monitored wheel, a receiving or controlling module in the car, and the dashboard warning display. The sensor measures the air pressure in the tyre and sends the result to the vehicle.
The pressure sensor is normally placed inside a tyre, either on the valve stem or fastened to the wheel.
Using a radio signal, the sensor informs the vehicle's receiving device about the pressure levels.
In this phase, the control unit compares the result with the vehicle's designated range of acceptable pressure levels.
The light of TPMS in the dashboard will only light up if the tyre pressure drops below the programmed limit.
Some types of direct TPMSs provide information on all four tyre pressures. For instance, the display on one TPMS may show a front left at 33 psi, a front right at 32 psi, a rear left at 34 psi, and a rear right at 33 psi. However, some direct-type TPMSs may simply illuminate the warning light without displaying numerical values.
What happens in an indirect TPMS?
An indirect TPMS doesn't have pressure sensors inside the tyres. It works by using wheel-speed information provided by the anti-lock braking system (ABS, for short), to detect a tyre that is behaving differently from the others.
If a tyre loses air, its effective rolling radius may be reduced. As a result, that wheel might rotate at a different speed from the remaining wheels. Indirect TPMS software compares the speed differences of individual wheels. If the software detects a loss of tyre pressure as the cause of a change in speed, a warning light is illuminated.
Since indirect TPMS is based on comparison, it may be necessary to calibrate or reset the system when tyres are inflated, rotated, or changed, or when wheel sizes are changed. The reset method varies by vehicle; for example, a button sequence or an infotainment menu step must be followed according to the user manual.
What does the TPMS warning light mean?
A TPMS warning indicates either that a tyre pressure is low or that there is a TPMS fault, depending on how the indicator reacts. It is not advisable to brush off the light as a small leak can lead to pressure loss in a tyre for days, or if a puncture is the reason then it could be a small puncture, it could be a leak from the valve, a leak from the rim, or natural air loss.
| Dashboard signal | Usual meaning | What to do |
|---|---|---|
| Solid TPMS light while driving | One or more tyres may be under-inflated. | Stop safely, check all tyres with a pressure gauge, and inflate to the vehicle manufacturer's recommended pressure. |
| Light turns on after a cold start, then goes off after driving | Tyre pressure may be close to the warning point, because pressure changes with temperature. | Check cold tyre pressure before the next drive and set it to the recommended value. |
| Light flashes, then stays on | Many vehicles use this pattern to show a TPMS malfunction rather than only low pressure. | Check tyre pressure first. If pressure is correct, have the TPMS sensors, receiver, or calibration checked. |
| Warning after tyre rotation or replacement | The system may need relearning, sensor pairing, or reset. | Follow the owner's manual reset process or ask the tyre shop to relearn the sensor positions. |
According to US Federal Motor Vehicle Safety Standard No. 138, the TPMS warning telltale should indicate underinflation in one or more tyres and specify the malfunction indication requirements. The way in which it is to be done is determined by the vehicle manufacturer.
What pressure should you set for the tyre?
The proper tyre pressure is the one recommended by the vehicle manufacturer, not the maximum pressure stated on the tyre sidewall. In most vehicles, you can find the required pressure on the driver's doorjamb, fuel filler cap, glove box label, or owner's manual.
Cold tyre pressure is the most precise pressure reading. The term 'cold tyre pressure' refers to the tyre pressure after the vehicle has been parked for several hours or driven a short distance at low speeds. When driving long distances on the highway, the heat generated increases tyre pressure; hence, the hot reading does not correlate with the cold recommendation.
For instance, if your vehicle's placard states 33 psi for all tyres, inflate them to 33 psi when cold unless another pressure is specified in the owner's manual. You should not inflate the tyre to the maximum number stated on the tyre.
What should you do when the TPMS light comes on?
Pull over if necessary
Do not brake abruptly just because of the TPMS light activation. Pull over slowly at a safe location when you sense any instability, or when you feel a tyre has been punctured.
Examine the tyres
Observe if there is any flat tyre, sidewall injury, nail, or any cut. It is not advisable to drive on a flat tyre since both the tyre and wheel could be easily damaged.
Check the tyre pressure
Use a pressure gauge to check all tyres’ pressures, including the spare tyre, especially when it has a TPMS sensor or when your vehicle manual instructs you to do so.
Reinflate the tyres to the recommended pressure
Inflate the tyres to the recommended pressure as shown in your car's manual. Inflate the tyres to 33 psi when the manufacturer recommends that pressure.
Reset the system if necessary
For an indirect TPMS or a resettable TPMS, follow the reset process outlined in the owner's manual after setting the pressure.
Repair the cause if it returns
If the tyre regains its air after correct inflation, have it checked for any leaks, such as slow punctures, valve leaks, rim leaks, failed sensors, or TPMS problems.
What are the limits of TPMS?
A TPMS is very helpful, but that doesn't mean tyre checks become a thing of the past. The warning might come only when the pressure is so low it reaches the threshold level programmed into the system. The tyre's lifespan, and of course vehicle handling and gas mileage, may be negatively affected even before that happens.
| Situation | What TPMS can do | What TPMS may not do |
|---|---|---|
| Slow pressure loss | Warn when the tyre reaches the system's low-pressure threshold. | Identify the exact cause of the leak without physical inspection. |
| Sudden puncture | Show a warning if the system detects the pressure drop in time. | Prevent loss of control or tyre damage if you keep driving on a flat tyre. |
| Over-inflation | Some advanced systems may show high pressure values. | Basic TPMS may focus on low-pressure warning only. |
| Wrong pressure after service | May warn if the pressure is low enough. | Know whether the pressure matches your loaded-vehicle requirement unless set and checked correctly. |
| Sensor battery failure | May show a malfunction warning. | Recharge a sealed wheel sensor battery. |
Do not use the sidewall number as your normal pressure
Follow the manufacturer's tyre pressure recommendations to inflate your car's tyres. Usually, the number printed on the tyre sidewall indicates the maximum allowable pressure for the tyre, not the correct pressure for your car.
Is direct TPMS better than indirect TPMS?
Direct TPMS and Indirect TPMS are primarily distinguished by their precision, physical components, maintenance, and the type of information they provide to the driver.
| Question | Direct TPMS | Indirect TPMS |
|---|---|---|
| Does it measure actual pressure? | Yes, it uses pressure sensors at the wheels. | No, it estimates pressure loss from wheel-speed behaviour. |
| Can it show psi values? | Yes, if the vehicle display supports individual pressure readings. | Usually no, because it does not measure pressure directly. |
| Does it need wheel sensors? | Yes. | No separate pressure sensor is needed. |
| Does it use ABS sensors? | Not as its main pressure-measuring method. | Yes, wheel-speed data is central to the system. |
| What happens after tyre rotation? | Sensor positions may need relearning if the car shows individual tyre positions. | The system may need reset or recalibration. |
| Common maintenance issue | Sensor damage, sensor battery failure, or valve-stem issues. | Incorrect calibration after pressure correction, tyre change, or rotation. |
Does TPMS work with nitrogen, tubeless tyres, and spare tyres?
Yes, the TPMS works well with nitrogen-filled tyres, since it tracks tyre pressure regardless of whether the tyre contains standard air or nitrogen and will indicate a pressure loss.
Yes, the TPMS works fine with tubeless tyres, since most cars today have them and the TPMS is designed for these tyres. The spare tyre would be tracked only when a sensor is present for that tyre, and the TPMS in your vehicle supports including the spare tyre pressure indication.
Key takeaways
TPMS stands for Tyre Pressure Monitoring System, which alerts the driver to under-pressure conditions and tyre malfunctions.
Direct TPMS uses tyre-mounted sensors to measure tyre pressure, while indirect TPMS calculates pressure loss from ABS wheel speed data.
The TPMS light indicates that all the tyres must be checked for pressure with a gauge and inflated to the recommended level.
Choosing to ignore TPMS alerts when driving with a significantly underinflated tyre increases the risk of accidents and complications during a comprehensive insurance claim due to such neglect.
If the pressure is 24 psi while the recommended pressure is 33 psi, the tyre pressure is 27.3% lower than recommended.
TPMS cannot substitute for a tyre pressure check, since the TPMS light may illuminate after the pressure has already dropped below the pre-programmed value.
Sometimes TPMS needs resetting after tyre rotation, tyre change, puncture repair, or wheel replacement.
Frequently asked questions
TPMS is important because it alerts the driver to low tyre pressure on the dashboard. It helps reduce the risk of an underinflated tyre, but you must still perform a manual tyre pressure check periodically.
If the tyre is not obviously flat and the car seems normal, you should be able to drive a short distance to a safe place or a tyre shop. In case the car pulls, vibrates, or the tyre looks flat, you should stop and check it.
Some reasons for a continued illumination of the TPMS indicator light after inflation include if the tyre pressure is still not at the right level, the pressure in another tyre is low, the system needs to be reset, or there is a problem with the TPMS itself..
No, because TPMS is designed to measure the tyre pressure, while ABS prevents the locking up of tyres. Indirect TPMS uses ABS wheel-speed sensors, but the two systems are different.
The direct sensors used in TPMS are typically placed within the wheel, near the valve stem, or on the wheel assembly. The indirect TPMS system lacks wheel-pressure sensors because it measures pressure loss using wheel-speed information.
TPMS sensors can rarely be fixed. Some cases may allow only the replacement of a serviceable valve. Usually, a sensor is replaced if its electronics, body, or sealed battery is no longer working.
About the authors
Nikhila PS
Written by · Senior Content EditorNikhila is a content creator with 6+ years in EdTech and motor insurance, turning complex policies into clear, engaging content. She enjoys exploring digital trends, social media, and art while planning her next short escape.
Rekhit Singh Kaushal
Reviewed by · Senior Director - Motor UnderwritingRekhit Singh Kaushal is Senior Director at ACKO, a leading digital motor insurance provider in India. With deep expertise in insurance strategy and innovation, he brings trusted insights on car and bike insurance to help drivers stay protected.
