TPMS is a system fitted to a vehicle which constantly monitors the pressures or pressure imbalance in the tyres and provides a warning to the driver if these fall below a certain threshold. However, TPMS should not be seen as a replacement for regular manual tyre safety checks. Two types of TPMS systems are fitted on cars today:
- Direct systems use radio sensors mounted inside of each wheel to measure the tyre inflation pressures – they ‘directly’ measure the pressure within each tyre and send the data to a control unit
- Indirect systems utilise the vehicle’s existing ABS sensors to measure and compare the rotational speeds of the tyres and vibrations to ‘indirectly’ calculate the pressure within the tyres.
Both types of system work with the vehicle’s main Electronic Control Unit (ECU) to alert the driver via dashboard warning lights to any pressure loss or variance issues.
How to use your TPMS
In order to assist you in monitoring the pressure in your tyres, all new cars are now equipped with a tyre pressure monitoring system (TPMS) which notifies you of any pressure issues.
To discover how your TPMS works and how you need to look after it, take a look at our animated video.
What you need to know about warning lights
The air pressure within your tyres is the most important factor in determining how well they perform. Pressure affects the tyre’s speed capability, load carrying capacity, handling response, wear rate and overall safety.
What’s more, under-inflated tyres will cause your car to use more fuel and emit more CO2 emissions. It’s therefore critical for your safety and comfort that your tyres are properly inflated in line with the vehicle manufacturers’ recommendations.
Tyre pressures should be manually checked when they are cold at least once a month or before a long journey. However, in order to assist you in monitoring the pressure in your tyres, all new cars are now equipped with a tyre pressure monitoring system (TPMS) which notifies you of any pressure issues.
To discover how your TPMS works and how you need to look after it, take a look at our animation below or click on one of the links on the left. Download our free Tyre Pressure leaflet or check our online pressure calculator.
If the TPMS warning light on your dashboard illuminates, this should not be ignored as there may be a problem with the pressure in one or more of your tyres.
If you see a TPMS warning while driving, find a safe place to stop your vehicle where you can manually check your tyre pressures against the vehicle manufacturers’ recommended settings. These details can be found in your vehicle handbook, inside the fuel filler flap or on a placard located on the driver’s door sill.
If you are unable to check your pressures yourself, either call for roadside assistance or locate your nearest tyre professional who will be able to help you. You can find the location of your nearest TyreSafe member by visiting our member dealer locator.
Servicing your monitoring system
To ensure your TPMS system continues to operate properly and reduce the likelihood of an MOT failure, it may be necessary to have the system serviced occasionally.
TPMS sensors are designed to last for many years and miles, however, after a certain period, the sensor’s internal battery will run out meaning a replacement is needed. In addition, sensors can become faulty or fail completely as a result of weather damage, corrosion or accidental damage caused when changing tyres.
To ensure the sensor remains in good condition, many manufacturers recommend replacement of the valve cap and core components every time a tyre is changed. When replacement TPMS sensors are fitted to your vehicle, your tyre fitter may need to programme the new component to the car using specialist diagnostic equipment.
If your TPMS sensor does develop a fault, under no circumstances should this be removed and replaced with a ‘standard’ non-TPMS type valve. Removing the sensor will not only reduce your safety on the road, it will also result in your car failing its MOT.
When did TPMS become mandatory?
Since November 2014, all new passenger vehicles sold in the EU must be equipped with a tyre pressure monitoring system (TPMS).
TPMS has been fitted to cars for many years but recently the mandatory fitment and maintenance of such systems has come into force.
The process began with the introduction of legislation on 1 November 2012, whereby all new models of cars sold in the EU had to have a TPMS fitted. This was broadened out in November 2014 to include every new passenger vehicle being required to have a TPMS before being sold.
In the UK on 1 January 2015, legislation came into force stating that for these vehicles, an inoperative or faulty TPMS sensor would result in an MOT failure.
Frequently asked questions
TYRE PRESSURE MONITORING SYSTEMS (TPMS) TPMS is a system fitted to a vehicle which constantly monitors the pressures or pressure imbalance in the tyres and provides a warning to the driver if these fall below a certain threshold. Such is the importance of correct inflation, TPMS is a very useful safety feature.
TPMS should not be seen as a replacement for regular manual tyre safety checks. Two types of TPMS systems are fitted on cars today. Direct systems use radio sensors mounted inside of each wheel to measure the tyre inflation pressures. Indirect systems utilise the vehicle’s existing ABS sensors to measure and compare the rotational speeds of the tyres, which are affected by their pressures. Both types work with the vehicle’s main Electronic Control Unit (ECU) to alert the driver via dashboard warning lights to any pressure loss or variance issues.
All passenger vehicles sold in the EU since November 2014 must be equipped with TPMS. Furthermore, with effect from 1st January 2015, all vehicles fitted with TPMS when new will need to have a fully functioning system when undergoing their annual MOT test. Inoperative or faulty TPMS systems will result in an MOT failure.
Yes. Runflat tyres should only be fitted to vehicles with a TPMS. Runflat tyres are designed to provide a limited run-on period following a puncture. These types of tyres can be identified by the “RF” marking found on the tyre sidewall. Runflat tyres are only designed to run for a limited period, at a maximum speed of 50 mph with a limited load carrying capacity.
If you drive a modern vehicle, chances are it will be fitted with a Tyre Pressure Monitoring System (TPMS) and most new vehicles are equipped with direct TPMS. However, many popular makes and models of car operate with an indirect TPMS, so it’s important to understand the differences between the two and how to maintain the systems.
Indirect Tyre Pressure Monitoring Systems (TPMS) do not have air pressure sensors inside the tyres. Instead, they detect a low tire by comparing relative wheel speeds via the Anti-lock Brake System (ABS) wheel speed sensors. When a tire loses air, its diameter decreases slightly.
The anti-lock brake system on your vehicle uses sensors which measure the rate of revolution of each wheel. Indirect TPMS typically relies on these sensors to interpret the relative size of the tyres on your vehicle. These feedback to an onboard computer system which can pick up relative tyre sizes when one wheel starts spinning faster than expected. The driver is then alerted accordingly.
Indirect tyre pressure monitoring systems do not actually measure tyre pressure, in that it isn’t using a gauge to process a pressure measurement. Instead its alerts are based on tyre rotation speed and concurrent calculations.
Direct Tyre Pressure Monitoring Systems use pressure monitors in each tyre that provide pressure levels, they do not simply rely on wheel revolution data from the anti-lock braking system.
Some direct TPMS will even provide tyre temperature readings. This vital information is then relayed to a centralised system which will interpret the data, which is then transmitted straight to your dashboard. If there is a problem with the pressure in one of your tyres, a warning light will illuminate on your dashboard. In most modern direct TPMS, this information is sent wirelessly and each tyre has a different sensor with its own unique serial number. This systems provides accurate and individual pressure readings for each tyre and does not rely on any other systems in the vehicle.
It is worth periodically servicing your TPMS to reduce the likelihood of an MOT failure, and most importantly ensure the system is operating correctly. Even though sensors are designed to last considerable mileage and time, the internal battery will eventually run out, requiring a replacement. In addition, sensors can become faulty or fail completely as a result of weather damage, corrosion or accidental damage caused when changing tyres.
To ensure the sensor remains in good condition, many manufacturers recommend replacement of the valve cap and core components every time a tyre is changed. When replacement TPMS sensors are fitted to your vehicle, your tyre fitter may need to programme the new component to the car using specialist diagnostic equipment.
Do not remove and replace with a ‘standard’ non-TPMS valve. Removing the sensor will not only reduce your safety on the road, it will also result in your car failing its MOT.
If the TPMS warning light on your dashboard comes on, this should not be ignored as there may be a problem with the pressure in one or more of your tyres. At the earliest opportunity, find a safe place to stop your vehicle where you can manually check your tyre pressures against the vehicle manufacturer’s recommended settings. These details can be found in your vehicle handbook, inside the fuel filler flap or on a placard located on the driver’s door sill. If you are unable to check your pressures yourself, either call for roadside assistance or locate your nearest tyre professional who will be able to help you. You can find further guidance on how to perform basic manual checks here
There are varying reasons why different vehicles are fitted with indirect or direct TPMS. Indirect TPMS is comparatively inexpensive to install and requires less maintenance. However, the trade off for this reduction is cost is arguably a reduction in accuracy and reliability. Direct TPMS deliver actual pressure readings from within each tyre from the moment you turn the vehicle on, however, indirect TPMS require the vehicle to be moving to provide a pressure reading. Indirect TPMS are also more prone to inaccuracies because of wheel replacements or rotation discrepancies.
Indirect TPMS can also become inaccurate if a different sized tyre is fitted to the vehicle and can also be inaccurate if tyres are worn unevenly.
One of the key disadvantages to indirect systems is that the driver may not see a warning light is the tyres are all underinflated by a similar amount. The system will not detect a problem if the rate of deflation is consistent across all the tyres. So it is possible that drivers could be driving on four underinflated tyres without being made aware.
Another key difference is in the maintenance of the different systems. Indirect TPMS need to be reset every time air is added or tyres are rotated to ensure accuracy. Although over time they require less maintenance and programming than direct TMPS, drivers must understand how to reset their systems if they add air to their tyres after performing regular tyre checks. If you are unsure, check your manufacturer’s handbook or consult a tyre professional.
Direct TPMS rely on sensors being in top condition, and incidents on the road including contact with the kerb, potholes or general wear and tear can cause damage to TPMS sensors, and they may need replacing. Furthermore, TPMS sensor batteries tend to last around ten years, and if they die, the entire sensor needs to be replaced. If you are unsure about the condition of your direct TPMS sensors, please check with a tyre professional who will examine them for you.
Whether your car is fitted with direct or indirect TPMS, it is still recommended to check your tyre pressures manually by using an accurate pressure gauge. This is to eliminate risks posed by technological faults and to ensure your tyres are correctly inflated. You can find the correct pressures for your vehicle in the manufacturers handbook, inside the door sill or fuel filler cap or by using our handy pressure look up.