What is TPMS and how does it work?
Tyre pressure monitoring systems (TPMS) are a safety feature on all modern passenger vehicles post November 2014. TPMS is a combination of hardware and software used to warn drivers when their tyre pressures are below a certain threshold (parameters set by the manufacturer) of the recommended pressure for that vehicle. Since November 2014 in the UK, manufacturers have been legally obligated to install TPMS on all new cars and light trucks to reduce accidents caused by incorrect tyre pressure. A TPMS lets drivers know when their car’s tyre pressure is low by activating an indicator light on the dashboard. This indicator light looks like a horseshoe with an exclamation mark inside it (though it actually depicts the cross-section of a tyre).
How does TPMS 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.
What does it mean when the TPMS light comes on?
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.
Is it safe to drive with the TPMS light on?
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.
How much does it cost to replace the tyre pressure sensor?
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.
Is TPMS required when replacing tyres?
Yes, TPMS have been a required safety feature (under EU regulation) since 2014.
How do you fix a TPMS sensor without replacing it?
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.
Tyre pressure and safety
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.
FAQs
Recommended tyre pressure varies based on the make and model of your car. The specific number (measure in pounds per square inch – PSI) can be found in the car’s manual or on a placard on the driver’s door post.
TPMS are not required to notify a driver of overinflated tyres. However, most TPMS do.
The TPMS reset button resets the TPMS when pressed after you have checked the pressure in the tyres are correct. To locate the reset you must refer to the vehicle handbook, as an example sometimes the button can be under the steering wheel. It is advisable that a trained tyre professional should reset Tyre pressure monitoring system.
If you see that your tyre is low or flat but the TPMS indicator light does not come on, chances are that you have a faulty sensor. Conversely, if the light comes on but all tyres have stable and correct pressure, this also may mean that you have a faulty sensor, especially if the light blinks when you first start the vehicle. Take your vehicle to a tyre service professional to have them check the sensors, however remember to insure your tyre pressures are checked and correct before driving.
In most cases, a TPMS can be transferred over to a new set of wheels. But before doing so, you should take into account the age of the sensors and the cost of potentially having to dismount and remount both sets of tyres to switch over the sensors.
Nearest dealer
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.
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