TPMS stands for Tyre Pressure Monitoring System which is a valuable safety feature which has been required to be fitted on all passenger cars in the United Kingdom and EU since November 2014 and has been fitted to all vehicles in the United States since 2008.
What is a TPMS? (Tyre Pressure Monitoring System)
A Tyre Pressure Monitoring System (TPMS) is an electronic system that monitors tyre air pressure and alerts the driver to the pressure in the vehicle tyres being adrift from the manufacturers recommended pressure by 25% or more.
Parts of the TPMS system are usually integrated into the car’s electronic control system and a light on the dashboard often accompanied by an alert noise will indicate to the vehicle user that there is an issue.
What is the purpose of a TPMS system?
The main purpose of a TPMS is to warn the driver when tyre pressure is too low, usually, this indicates that the pressure dropped below a minimum tolerance level or by a 25% or larger deviation from the manufacturer’s recommended pressure.
Maintaining the correct tyre pressure helps to prevent uneven tyre wear, and potential tyre blowouts but also helps to improve fuel efficiency and both ride and steering comfort.
What are the types of TPMS?
There are 2 different types of TPMS Systems, Direct TPMS and Indirect TPMS.
Indirect TPMS uses the ABS system to determine potential differences in tyre pressure, and Direct TPMS uses 4 dedicated sensors, one for each wheel to detect an accurate pressure reading for each tyre.
Indirect TPMS Systems
With indirect TPMS, the vehicle uses a combination of data collected from both the Anti-lock Brake System (ABS) wheel speed sensors and traction-control system to calculate the rate at which each wheel rotates, this helps to determine if a tyre has a reduction in pressure compared to the other wheels.
Indirect TPMS systems do not have TPMS Sensors inside the tyre or wheel rim and do not use the actual PSI to determine the pressure inside the tyre.
The theory behind indirect TPMS is that the circumference of a tyre will be decreased slightly as it loses pressure or deflates, and hence the rolling resistance of the tyre increases, and it is this data that the car’s computer will use to determine that one or more of the tyres has lost pressure.
What this means is that there is no need to fit individual TPMS tyre valves.
The downside of indirect TPMS is that the readings tend to be less accurate than direct TPMS as they are not tyre-specific readings, but rather an assessment looking for inconsistencies across the 4 wheels of the vehicle.
Direct TPMS Systems
Direct TPMS involves a sensor being installed inside each wheel or wheel valve, which can detect the pressure within an individual tyre, and the readings collected from these are sent to the car’s computer which monitors them constantly looking for a deviation from the manufacturer-recommended inflation PSI by 25% or more, and alerting the driver if this tolerance level is hit.
As per the products sold by Concept Garage Equipment, the direct TPMS sensors are very accurate and have been the tyre industry standard since 2014 in the UK and EU. These are fitted, replaced or inspected as part of any car tyre replacement or replacement of the tyre valve.
Please note: unless otherwise stated all other information on this website and TPMS product data that we sell relates only to Direct TPMS Systems.
How Does TPMS Work?
A TPMS system uses sensors to monitor tyre pressure and feeds this data back to the car. If one or more of the tyres has a change in tyre pressure outside of a tolerance level set by the manufacturer, then the system will show a warning light on the dashboard and often an audible alert to inform the driver that the tyre pressures need to be corrected.
How do TPMS sensors work?
A TPMS sensor is an individually battery-powered air pressure sensor that is fitted either to the wheel rim or as part of the tyre valve, such that it sits inside the pressurised area of the tyre but against the solid rim of the wheel.
The sensor is constantly communicating with the car’s computer so that it
- Knows what the pressure for each tyre should be based on the manufacturer’s recommendations for this car, wheel and tyre size
- Reports back when this pressure deviates by a predetermined amount, usually 25%. From the recommended tyre pressure
When this change in pressure is detected a warning light will show on the dashboard to warn the driver.
When the tyre pressure has been corrected by the driver, or local garage, or following a tyre or valve change, then it may take several revolutions of the wheel for the TPMS sensor to be fully re-calibrated and reading the corrected new tyre pressure, and for the warning light to be extinguished.
Is TPMS on the rim or tyre?
Cars with TPMS will typically have a sensor for each wheel, and these most commonly form the part of the tyre valve that is inside the wheel rim, and hence inside the tyre.
Some manufacturers use Banded TPMS sensors that are not part of the valve but instead sit in a cradle that attaches to the wheel rim 180 degrees away from the tyre valve by use of a strap or band, this is also inside the tyre when mounted on to the rim and hence is able to read the PSI of the tyre and send back to the car’s computer in the same way as TPMS valve sensors.
How to tell if tyres have TPMS installed
There are a few ways to determine if a vehicle has TPMS fitted
- The age of the vehicle, as all cars since November 2014 have been manufactured with TPMS a simple check on the age of the car could be enough to determine of TPMS is fitted
- Check for a TPMS warning light on the dashboard, as any vehicle with TPMS will have this, although it may not be illuminated, you may be able to see it light up when you first engage the ignition
- If you are removing the tyre or valve, a visual inspection around the wheel rim within the area that the tyre usually covers, looking for a small box at the back of the valve, or a box strapped or attached to the rim itself would likely show you that TPMS is installed
What pressure triggers TPMS?
The tyre pressure dropping or increasing by 25% compared to the manufacturer’s recommended setting would usually trigger the TPMS warning light and potentially a brief audible alarm also.
Check the vehicle handbook for the recommended tyre pressures for this vehicle, with this size of the wheel rim and both size and type of tyre, as these may differ even on the same make and model of vehicle.
Some vehicles also have the tyre pressure recommendations on a sticker inside the driver’s door jamb or placard, otherwise, contact the manufacturer or check online for recommended tyre pressures.
Is TPMS required when replacing tyres?
The law states that all passenger cars in the United Kingdom and EU since November 2014 must be fitted with some form of TPMS system. This may be direct or indirect, though most commonly in the UK the direct TPMS system is fitted to vehicles, and this has to be maintained or replaced when fitting tyres, or changing valves.
When a tyre is being removed, be sure to take extra care not to damage the TPMS monitor, as these can usually last without replacement for between 5 and 10 years or up to 100,000 miles but if suitable care is not taken they are easy to snag and break with a tyre iron for example, and the replacement can prove costly.
Is it worth it to replace TPMS sensors?
If the vehicle is fitted with TPMS sensors, and these are working fine then there is no reason to replace them. If the tyres are being replaced for example, and suitable care is taken during the removal and replacement process, then the TPMS sensors should continue to work and record the tyre pressures from the first few revolutions of the new tyres when the car is driven.
However, if one or more of the sensors is faulty, or is damaged whilst changing the tyres, then this must be replaced to maintain a fully functioning TPMS system, as a faulty TPMS system will result in an MOT failure.
How often do TPMS sensors need to be replaced?
A TPMS sensor valve contains a small battery and can last between 5 and 10 years or up to 100,000 miles and is generally determined by the life expectancy of the lithium-ion batteries inside the TPMS Valve itself, although this can vary depending on vehicle use, tyre damage or replacement, since the valve can be damaged whilst tyres are being changed, equally if the valve stem needs replacement sooner then either this or the whole TPMS valve may need to be replaced at that time.
Can a pothole damage TPMS?
Yes, it is possible, as driving over a pothole can damage the tyre and in extreme cases even the wheel rim. It can puncture the tyre or the sidewall of the tyre leading to a deflation of the tyre.
When the car computer senses the deflation of the tyre the TPMS light on the dashboard will illuminate, but continuing to drive on the deflated tyre could lead to catastrophic damage to the tyre, wheel rim and potentially to the TPMS valve or sensor also.
Will changing wheels affect TPMS?
If the wheels are being changed for the same type exactly, with the same rim size, and same tyre type and size, then the TPMS sensors would need to be removed carefully from the old wheels and added into the new ones, and these should continue to work as they did previously, assuming the tyre pressures are set to the same as previously and the vehicle may need to be driven for a few rotations of the tyre for the TPMS system to re-read the pressures.
However if different wheels, with potentially different rim sizes, and different tyre sizes, with potentially different pressures are being used then the TPMS monitors will either need to be re-programmed to account for these differences or in extreme cases the TPMS valves may need to be completely replaced, especially if these were damaged during the change of wheels and tyres.
What happens if you don’t replace TPMS sensors?
If you change your wheels, and tyres or even swap between summer and winter tyres, then your TPMS monitors need to be considered as an essential part of the process.
As a minimum, the TPMS monitors must be re-calibrated or re-programmed to cater for the difference in tyre, size and pressure. Failing to do this could mean that the TPMS either does not work at all or will be registering the tyre pressures incorrectly, leading to false alarms or unsafe driving pressure in your tyres.
Can you fail MOT for the TPMS light?
Not necessarily. If a warning light relating to the tyre pressure monitor system suggests that the system is faulty then this is an MOT failure, but simply having the TPMS light illuminated due to reduced pressure is not in itself an MOT failure.
The MOT inspection manual states that:
The inspection of the tyre pressure monitoring system (TPMS) is for M1 vehicles first used on or after 1 January 2012.
The TPMS warning lamp can operate in many ways depending on the vehicle type. You must only reject vehicles if it’s clear that the lamp indicates a system malfunction and not simply indicating that one or more of the tyre pressures is low.
Tyre pressure itself is not checked as part of the MOT, however, the TPMS light being illuminated may result in further investigation and delays to the MOT pass, so it is always best to ensure that tyres are properly inflated to manufacturer standards and that no other issues are prevalent with the TPMS system before completing the MOT.
How to remove a TPMS sensor
Before starting work, check if this vehicle is fitted with TPMS, you can do this by checking the vehicle’s year of manufacture and also check for a TPMS light on the dashboard.
Remove the valve stem core to relieve the pressure, before breaking the tyre bead, but do so carefully as the TPMS monitor may either form part of the tyre valve (TPMS valves) or may be installed in a separate unit attached to the wheel rim on the opposite side of the wheel to the valve (Banded TPMS sensors), and the bead breaker can damage this if it impacts the TPMS sensor.
Now you have 2 choices, you can either
- Remove one side of the tyre from the rim, to expose the TPMS sensor for removal or
- Remove the whole tyre before dealing with the TPMS valve or sensor
The TPMS sensor may either be held in place in its own cradle which is attached to the rim in the case of a Banded TPMS, but most likely (and most common) is that it will be attached to the inside end of the tyre valve.
In the case of the TPMS valve, you can remove the whole valve from the rim, by removing the valve stem nut and pushing the TPMS sensor in from the outside of the rim.
The alternative is that you can unscrew the TPMS monitor from the rear or inside of the valve using the correct size screwdriver, hex bit or special tool supplied with the TPMS valve – this would leave the valve stem in place, for example, if you are planning to simply replace the TPMS monitor part and not the valve stem.
How to replace TPMS valves or TPMS sensors
First, check that TPMS is fitted to this vehicle by checking the age of the car and the TPMS symbol on the dashboard. Next, you need to release the air from the tyre and carefully break the bead. On the tyre, be mindful that you don’t damage the TPMS sensor inside.
Next, you need to gain access to the TPMS monitor either by removing one or both sides of the tyre from the wheel rim, and then removing the TPMS valve with the tools supplied, these are usually either a tool specific to this TPMS valve, a hex bolt, or some can be removed with a screwdriver.
Now check the TPMS monitor you plan to fit, ensure it is the correct type and size, and that it has been programmed to this make and model of vehicle, for the correct tyre size and pressure.
Now the old TPMS monitor has been removed, the replacement is a reverse of removal. Fit the new TPMS valve or sensor into place, then re-fit the tyre, taking care not to damage the TPMS monitor in the process.
Fit the valve core and inflate the tyre to the correct pressure.
There may be a relearn procedure, or some vehicles simply need to be driven around for a few rotations of the tyre for the sensors to communicate with the car computer TPMS system correctly again.
Can you remove and reuse TPMS sensors?
Yes, you can reuse both your manufacturer-installed tyre pressure monitoring sensors as well as aftermarket TPMS valves and sensors. Just be sure to practise care when removing and refitting tyres as TPMS sensors can easily be damaged with tyre-changing tools and tyre-changing equipment. Also, you must ensure that the TPMS sensors are properly calibrated once they have been installed on the new wheels or inside the new tyres.
How much does TPMS cost to replace?
There are several parts to consider in a TPMS system.
Standard TPMS sensors with valve stem built-in cost in the region of £30 each.
The valve stems that can be replaced separately usually come in packs of 10 or more, and are around £5 each.
Alongside these there are several ancillary items such as nuts, washers, valve caps and valve cores, these often come as a kit for anywhere from around £20.
By far the most expensive part of any TPMS system (apart from the car!) is the diagnostic tool used to read from and write to the TPMS sensors, and these are essential if you are working on multiple vehicles, as it enables you to use TPMS valves and sensors across a range of vehicles, by encoding them to each vehicle, rather than buying a single set of TPMS sensors for a single vehicle make & model.
These TPMS diagnostic machines can range from a mobile phone application to several hundred or even thousands of pounds depending on the capability of the diagnostic tool and the range of valves and vehicles it is suitable to use it on.
Note: Prices depend on the supplier, but are correct at the time of writing November 2022, but will likely change over time.
How can I make sure my TPMS is working?
When you turn on the vehicle ignition the TPMS light should light for a short period of time and then extinguish – this indicates that the system is functioning and operating normally.
If the TPMS light stays on then it would indicate that one or more of the tyres are at least 25% below or above the recommended inflation pressure.
If the light flashes, changes colour or is accompanied by an alarm or beep, then there may be a problem with the TPMS system.
Refer to the user’s handbook or maintenance manual for this specific vehicle as each make and model could have different meanings for the set of symptoms seen.
Do you need to reset TPMS after new tyres?
If you have removed, repaired and refitted, rotated, or replaced tyres then the TPMS system may need to be reset, calibrated and always checked to ensure it is operating correctly.
If the tyres were swapped with like for like, and the recommended tyre pressures are the same, then the settings on the TPMS system should still be correct, but inflate the tyres to the recommended pressure, and drive the car for a few minutes to ensure the TPMS light is extinguished and everything is operating as it should.
If the tyres, or indeed the wheels have been changed for different types, then the TPMS system settings will likely need to change, and you will need a TPMS diagnostic machine to do this. Depending on whether these are manufacturer-fitted TPMS sensors, hybrid aftermarket, or other types of universal TPMS sensors, then some may need a visit to the dealership to be properly reset, but if you have the correct TPMS diagnostic machine for the TPMS valves or sensors fitted then setting them up for the new settings should not be a problem.
What is the best tyre pressure monitoring system?
There are several manufacturers of TPMS systems, as well as the OEM manufacturer’s systems and TPMS Sensors fitted when the vehicle leaves the factory, several aftermarket suppliers now have universal valves that are not vehicle specific and can be programmed using the suitable TPMS diagnostic tool to fit most makes & models of vehicle. For most garages, other than vehicle make specific dealerships, these hybrid TPMS systems are the best in terms of cost-effective systems, as the TPMS valves can be bought and programmed to the correct vehicle as required, therefore reducing any wastage or having to buy TPMS valves and sensors for every kind of vehicle that may drive in needing tyres changed.
The best systems for programming TPMS sensors will have a vehicle-specific database for domestic, Asian and European vehicles to cover the majority of cars in the UK, as well as programming there should be a diagnostics mode for easy TPMS problem-solving, and batch programming to be able to encode multiple TPMS sensors at the same time.
How much does a TPMS system cost?
The main component of a TPMS system for a garage to use is the diagnostics tool for programming the TPMS Sensors. If you work on multiple makes and models of vehicles you will need a TPMS programming tool for encoding universal TPMS sensors as these can easily be adapted to work on any car.
These TPMS diagnostic machines can range from a mobile phone application to several hundred or even thousands of pounds depending on the capability of the TPMS programming tool and the range of valves and vehicles it is suitable to use on.
Other than this, the consumables which are the parts which fit into the car wheel are the TPMS Sensors, the TPMS valve stems and the ancillary fittings for these to attach to the wheel inside of the tyre, and these are generally between a few pounds up to hundreds if you are buying your TPMS valves and TPMS sensors in bulk as some garages and workshops do, especially those that specialise in tyre changing or mobile tyre fitting.
Note: Prices depend on the supplier, but are correct at the time of writing November 2022, but will likely change over time.
Is a tyre pressure monitoring system accurate?
Direct TPMS sensors are very accurate and these have become the de-facto standard form of tyre pressure monitoring since 2014 in the UK and EU because of this reason.
Indirect TPMS systems which use the Anti-lock Brake System (ABS) wheel speed sensors and traction-control system to calculate the rate at which each wheel rotates tend to be less accurate and as a result are less popular.
In 2016 Garagewire exposed that some car makers were manipulating the lab tests of indirect TPMS systems and this may have somewhat attributed to direct TPMS systems being the preference for many car manufacturers and customers alike.
How does a tyre pressure monitor system work?
A tyre pressure monitor system also known as a TPMS uses sensors to monitor tyre pressure and feeds this data back to the car. If one or more of the tyres has a change in tyre pressure outside of a tolerance level set by the manufacturer the system will show a warning light on the dashboard and often an audible alert to inform the driver that the tyre pressures need to be corrected.
Is it OK to drive with the TPMS light on?
If the TPMS light is illuminated, then it is highly recommended that you stop the vehicle and check the information on your vehicle tyres immediately.
Without checking the tyres and the inflation levels you could be driving around with significantly under, or over inflated tyres, decreasing your traction on the road, along with your ability to steer or corner correctly, and increasing the risk of injury to yourself and the other road users.
The recommended action is to stop, check the condition of the tyres and the level of inflation in each tyre using a calibrated tyre pressure gauge, and correct any under or over inflation.
In the case of the tyre(s) being under-inflated this could be due to a number of factors, for example, you may have a puncture, a broken tyre bead or a leaking tyre valve, and these also need to be corrected before continuing your onward journey.
Why is my TPMS light on but the tyres are fine?
If you have checked all tyres and the tyre pressures are correct and in line with manufacturers’ inflation levels, then the most common reason for this would be that one or more of the TPMS sensor’s batteries is failing or has failed.
Another possible reason could be that the TPMS monitor was damaged during the replacement or repair of a tyre.
In both of these circumstances, the TPMS sensor would need to be inspected and potentially replaced.
What causes TPMS malfunction?
TPMS issues can be caused by one of the following:
- The TPMS sensor battery has failed or died
- One or more TPMS sensors have been damaged during a tyre change or repair
- The TPMS module is not receiving a signal from one or more sensors because of an antenna or wiring fault
- The TPMS sensor could be programmed for the wrong vehicle or pressure, which can happen if tyres or wheels are changed, but TPMS sensors are not re-programmed
How do I get the TPMS light off?
If the TPMS light is illuminated then the first thing to do is to check all tyre pressures, inflate all to the recommended tyre pressure, and drive the vehicle for a few minutes to ensure the TPMS light goes off.
If the TPMS light remains on after correctly inflating the tyres to the manufacturers recommended pressure, then here are some additional things to try
- Drive the car at 50 mph for about 10 minutes. This will often reset the TPMS tyre sensors
- Inspect the tyres and valves to ensure there are no leaks, or valve issues causing the tyre to deflate
- Use the TPMS diagnostic tool to diagnose the issue
- Check the manufacturer’s instruction manual, or TPMS Sensor manual to check for additional issues common to the vehicle being inspected
Can a TPMS reset itself?
If you have not changed the tyres and have not removed or replaced the TPMS sensors, but are simply inflating or deflating the tyres to correct a TPMS light being on then you do not need any special tools to reset the system. Simply inflate or deflate the tyres and then drive the car for a few minutes and the TPMS system should reset itself.
However, if the wheels, tyres or TPMS sensors have been changed, then the TPMS sensors will likely need to be programmed or replaced in line with the changes made.
Will over inflated tyres cause the TPMS light to come on?
Yes, the TPMS systems on cars are used to determine incorrect tyre pressure, and any deviation, usually by 25% or more from the recommended inflation will cause the warning light to be illuminated, and this includes both under inflation and over inflated tyres.
Help with your TPMS Sensors or TPMS Programming Tool
If you are considering adding TPMS to your garage offering speak to Concept Garage Equipment first. We can advise on the best equipment to purchase to get you started in TPMS without breaking the bank or buying too much stock, by using our TPMS programming tools and TPMS sensors you can keep your stock levels to a minimum whilst always being able to cater to 99% of major car makes and models that come through your MOT Bay or Garage door. Don’t forget even if you use mobile tyre fitting equipment you should have your TPMS valves and diagnostic tool with you for changing tyres on the drive too.
We can offer you advice over the phone at 0113 469 0572, we sell TPMS Valves, TPMS Sensors and TPMS Programming tools over the phone, and as with everything we sell, all product prices include delivery as well as free advice on the best use of the equipment, or indeed any other garage equipment up to a full MOT Bay.
Note: All information, data, facts and prices are correct to the best of our knowledge at the time of writing November 2022, but will likely change over time.