What is TPMS and how does it work?

There are two main kinds of TPMS: direct and indirect. A direct TPMS measures tyre pressure directly via a pressure sensor attached to the back of each tyre’s valve. This sensor is battery powered and transmits data to the vehicle’s central computer. An indirect TPMS collects data from existing sensors, such as ABS and wheel speed sensors, which is then interpreted by software to infer the tyre pressure. This kind of system makes use of the fact that low tyres rotate at a different speed than correctly inflated ones. Either system will activate the tyre pressure symbol on the dashboard when pressure falls significantly below the recommended pressure for the vehicle.

When the TPMS light is on, it most likely means that the system is performing exactly as designed: alerting you that your tyre pressure is outside the recommended range. You should manually check the tyre with a gauge and inflate or deflate the tyre to the manufacturer’s recommended pressure setting.
If the light is on but you find that that the tyre pressure is correct, the system may be malfunctioning. Another possible sign of a faulty sensor is a TPMS indicator light that blinks when you start your car and then remains on. Temperature can also affect tyre pressure, so if the TPMS light is alternating on and off, it may be that excessive heat or cold is pushing the pressure beyond the recommended values.

If your TMPS light is on, you should always assume that your tyre is underinflated and check it as soon as possible. Underinflated tyres do not perform correctly and can lead to blowouts, loss of control and poor handling. They are the cause of an average of 1,500 serious accidents per year in the UK alone, so it’s an issue that shouldn’t be taken lightly. If you check your tyre pressure and none of your tyres are low, it may be okay to keep driving slowly and carefully with the TPMS light on but you should fix the problem as quickly as possible at your nearest garage.

A tyre pressure sensor’s price tag will depend on your car model and the part it requires. It is generally necessary to replace the sensor and the batteries together – they are usually a single unit. For the part and labour, you can expect to pay anywhere from £12 per sensor to over £150, depending on your vehicle.

Yes, TPMS have been a required safety feature (under EU regulation) since 2014.

TPMS sensors most often need to be replaced because their batteries have reached the end of their 5- to 10-year lifespan, although they could be damaged sooner by road conditions. Most sensor models have built-in, non-replaceable batteries, so the only solution is to replace the whole sensor. In some instances, problems with the valve stem can be fixed without putting in a complete new sensor unit via the use of sensor stem service kits. It is recommended that you have your TPMS sensor serviced every tyre change to prolong the lifespan and accuracy of the sensor.

You should always try to keep your tyres inflated to the pressure recommended by your vehicle manufacturer. When tyres are operated at improper pressures, the tyre’s sidewalls can flex and damage the belting structure in the tyres. You will not be able to see this damage, which can increase over time. This is why you should maintain proper inflation pressure and try to avoid driving when the TPMS light is on. If you absolutely must drive a short distance on a tyre with severely low pressure, drive very slowly and use extreme caution. The tyre should be inflated or changed before driving anywhere.

If you still have questions about your TPMS or suspect that your system or tyres are not functioning properly, get help from your nearest tyre dealer so you can stay safe on the road.