What is TPMS & How Does it Work?

What is TPMS & How Does TPMS Work?

TPMS stands for tyre pressure monitoring system, it consists of small electric sensors fitted to each wheel of the vehicle to monitor tyre pressure and feed this data back to the car. Should one or more tyre see a change in air pressure, the system will show a yellow warning light on the dashboard to alert the driver. All new cars in the UK manufactured after 2014 are fitted with TPMS and any vehicle with a faulty or inoperative system will fail its MOT test. 


What are the Benefits of TPMS?

Having TPMS fitted to your vehicle provides the following safety and handling benefits:

  • Provides visual warning of low pressure whilst travelling
  • Reduces risk of tyre failure due to early warning
  • Helps to ensure optimal tyre pressure
  • Decreases tyre wear from incorrect pressure levels
  • Maintains vehicle handling
  • Helps to provide optimum fuel economy 

How Does TPMS Work?

TPMS works by monitoring tyre pressures with sensors – if the pressure changes above or below a certain point an alert is shown on the dashboard. There are two different types of pressure monitoring systems – direct and indirect that work differently. 



How Does Direct TPMS Work?

Direct TPMS works via air pressure sensors in each wheel on the valve of the tyre, that monitor the pressure within the tyre – these systems are usually able to provide these real time readings for each tyre along with temperatures. The system then transmits this information wirelessly to the car which creates an alert on the dashboard should the pressure change.

Advantages of Direct TPMS
Disadvantages of Direct TPMS

Provides a reading on the actual tyre pressure

Easier to damage sesnors during changing/maintenance of the tyre

Better acurracy of reading

Expensive system in comparison to indirect

Does not require a reset following tyre inflation or rotation

Lifetime of sensor/battery lasts longer

How Does Indirect TPMS Work?

Indirect TPMS works differently, without the use of air pressure sensors in the tyres. Indirect systems detect a loss in pressure using the ABS wheel speed sensors to read the relative wheel speed to create pressure readings to compare between all 4 tyres. The theory behind this system is that once a tyre is under-inflated it begins to rotate faster than expected – which will then lead to an alert being sent to the dashboard.   

Advantages of Indirect TPMS
Disadvantages of Indirect TPMS

System is cheaper than direct TPMS

Does not provide an accurate reading of tyre pressure

Needs less system collaboration or maintenance compared to direct systems

May provide incorrect reading if new tyres are different sizes

Requires resetting after tyre maintenance – rotation, inflation, etc.








TPMS Legislation

TPMS is now a mandatory fitment in all new vehicles in the UK as of 2014. From 2015 onwards inoperative or faulty TPMS sensors would lead to a failed MOT.


How to Tell if Your Car has TPMS

If your vehicle is 2014 or newer it is likely to have TPMS. You can check if you have TPMS by checking for the TPMS light when turning your key in the ignition without starting the engine – causing all dashboard lights to show. If you have RunOnFlat or Run Flat tyres, you’ll also have TPMS. The owner’s manual will also detail if you have TPMS and which system.


TPMS Maintenance

TPMS can be serviced by your local tyre dealer – especially when fitting new tyres to ensure that the system is collaborated correctly to the right tyre size and recommended pressures. Tyre pressures should also be checked manually on a regular basis as well as carrying out checks on the general health of the tyre such as tread and sidewalls, a guide to this can be found here.


What to do if Your TPMS Light Comes On

If your TPMS light comes on whilst driving you should stop as soon as it is safe to do so in order to check the tyre pressure of all of your tyres manually using a gauge to identify which tyre is having pressure issues in order to decide if a tyre change is needed or whether it is safest to head to the nearest garage. 


TPMS FAQs

How Long Do TPMS Sensors Last?

The battery life of direct sensors can last between 5-7 years, whereas indirect systems utilise the ABS of the vehicle requiring no additional batteries. 

Will the TPMS Light Come on if Over-inflated?

Check with the vehicle or TPMS manufacturer to understand whether your system has this option available.  

How Far can I Drive with the TPMS light on?

It is recommended that once the TPMS light is on the dashboard to pull over as soon as it is safely possible to do so to check all 4 tyres for any damage. From here you will need to establish whether to change the tyre or visit the nearest garage for help. 

Can I Remove the TPMS Sensor?

It is not recommended to remove the TPMS system as it is there to provide a safety warning should the tyre pressure change. New changes to UK automotive legislation now means from 2021 the UK no longer has to comply or enforce EU regulations on TPMS – however, if you plan to drive your vehicle in the EU your vehicle will have to comply with that country’s laws.

Where is the TPMS Sensor Reset Button?

In most vehicles, the TPMS reset button is located under the steering wheel – otherwise, the location of the button will be detailed in the owner’s manual.

How to Replace TPMS Sensor Battery?

As most batteries are attached the to the sensor, it’s often not possible to replace the battery alone without also replacing the sensor. It is recommended to visit your local garage for help and advice on your specific TPMS battery. 

What Should I Do if my Warning Indicator Comes on?

If the warning indicator is showing on the vehicle dashboard you should pull over as soon as it is safe to do so. If your TPMS does not show the air pressure in each tyre to identify the issue, you should check all 4 tyres for any signs of puncture or damage. This will allow you to assess whether to change the tyre or continue your journey to the nearest garage

Can I add TPMS to my Car?

It is possible to retrospectively fit TPMS to an older vehicle using an aftermarket kit that is easy to install or can be installed by your local garage. The reading system can be displayed using power from a cigarette receptacle which will alert you should the pressure change in your tyres. 

How to Read TPMS Sensor ID?

The sensor ID is located on the sensor itself – or is discoverable with a TPMS tool that is held close to the tyre sidewall which encourages the sensor to transmit its ID and other information. 


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