Most drivers first meet TPMS as a small amber light on the dashboard. The system behind it is straightforward: it keeps an eye on tyre pressure and speaks up when something is wrong, long before a soft tyre is obvious from the driver's seat.
What TPMS does
TPMS stands for Tyre Pressure Monitoring System. Its job is to warn the driver when a tyre has lost enough pressure to affect safety, using a warning light on the dashboard. A tyre can be several PSI low without looking flat or changing how the car feels, and a slow puncture can bleed away over days. The system is there to catch exactly that, the gradual loss that is easy to miss.
It matters because pressure is the single setting that touches grip, braking, fuel use and tyre life all at once. An under-inflated tyre runs hot, wears at the edges and lengthens stopping distances, so an early warning is worth having.
Why every newer car has one
TPMS is not optional on modern cars. New passenger car models had to include it from November 2012, and every new car registered in the UK from 1 November 2014 has carried it since. That is why a 2015 hatchback has the system and a 2010 one often does not.
There is a legal edge to it too. For cars first used on or after 1 January 2012, a TPMS that is broken or flagging a fault has been an MOT failure since January 2015. A light stuck on for a dead sensor is treated as a tyre-related MOT defect, not a cosmetic niggle, so it is worth putting right rather than living with.
The two ways it works
There are two designs, and which one a car has changes how it behaves day to day:
- Direct TPMS uses a small battery-powered sensor inside each wheel that measures the actual pressure and radios it to the car. It can show a real figure and pinpoint the low tyre.
- Indirect TPMS has no pressure sensors at all. It borrows the ABS wheel-speed sensors and notices when one tyre is spinning slightly faster than the rest, which happens when it goes soft and its rolling radius shrinks.
The practical differences, accuracy, resetting and what happens at a tyre change, are covered in the comparison of the two systems.
What it is not
TPMS is a backstop, not a babysitter. It is set to warn at a pressure already low enough to be a problem, often around 25% below the recommended figure, so a tyre can be down a few PSI, costing fuel and tread, with the light still off. The habit that actually keeps pressures right is a monthly check with a gauge against the figure on the car's placard. On a direct system, the sensors live inside the wheel and are serviced, new seals and valve cores, or a replacement when the battery dies, whenever new tyres are fitted, part of the job when a set ordered online from Tyres.co.uk goes on.
From the workshop: the number of people who think the light means "top up a bit and it'll go off" is huge. Sometimes that's all it is. But just as often it's a nail picked up that morning, and the tyre's already halfway down. Treat it as "check all four now", not "deal with it later".
Sources and accuracy. The fitment dates and MOT rule here reflect UK type-approval and DVSA requirements at the time of writing and can change. Anything safety-critical should be confirmed against current official guidance. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
What does TPMS stand for?+
Tyre Pressure Monitoring System. It is the system that watches the pressure in a car's tyres and warns the driver, through a dashboard light, when one is running low.
Do all cars have TPMS?+
All new passenger cars sold in the UK have had to carry TPMS since 1 November 2014. Cars registered before then may not have it, as it was not required. Vans and motorhomes were not covered by the same rule.
Does TPMS replace checking pressures by hand?+
No. TPMS is a safety backstop that flags a tyre already low enough to matter, not a substitute for a monthly gauge check. By the time the light comes on, a tyre is often well below its proper figure.
Is a faulty TPMS an MOT failure?+
Yes, for cars first used on or after 1 January 2012. Since January 2015 a TPMS that is not working or is signalling a fault counts as a major defect and fails the MOT, so it cannot simply be ignored.