The TPMS light means at least one tyre is 25% or more below its recommended pressure, OR a tyre pressure sensor has failed. Check all four tyres cold against the door-jamb sticker — a 2-minute top-up clears most cases.
Here's a quick, honest answer from a working UK mechanic — what causes it, what it costs to fix, and what to do next.
What the symbol actually means
The TPMS (Tyre Pressure Monitoring System) light is the exclamation mark inside a horseshoe — sometimes shown as a flat tyre cross-section. UK and EU law has required it on every new car since November 2014, and a permanently-lit TPMS warning is now an MOT fail under the major-defect category. The system is doing one of two things: telling you pressure has dropped (solid light), or telling you the system itself has failed (flashing light for 60–90 seconds then solid).
Check this first — before you book anything
Drive to your nearest petrol-station air pump and check all four tyres cold (or after no more than 2 miles of driving). The correct pressures are on a sticker inside the driver's door jamb or inside the fuel-filler flap — not always what the tyre wall says. Top each tyre to spec, then drive 5–10 minutes. On most cars the light will clear itself. On some (BMW, Mini, Mercedes) you have to hold the TPMS reset button or use the dash menu to reset after re-inflating.
Why it usually comes on in autumn and winter
Tyre pressure drops roughly 1 psi for every 10°C the temperature falls. A car set to 32 psi in summer can read 27 psi on a cold November morning — enough to trigger the warning on a sensitive system. This is the single most common reason Bob sees TPMS lights in the UK between October and March. Pump them back up to the door-sticker spec and the light usually clears.
The two TPMS system types
Direct TPMS uses a battery-powered sensor inside each wheel (typically lasting 5–10 years). When the battery dies, the sensor goes silent and the light comes on permanently. Indirect TPMS uses the ABS wheel-speed sensors to detect a tyre rotating faster than the others (a low tyre has a smaller rolling diameter). Indirect systems are cheaper but less precise — they need to be reset after every pressure adjustment via the dash menu.
Common causes the air pump will not fix
(1) A slow puncture from a screw or nail — the tyre re-inflates fine but is back down within 48 hours. Visual inspection or a soapy-water test usually finds it. (2) A leaking valve core or corroded alloy bead — both common on UK roads after a few winters of salt. (3) A failed TPMS sensor battery — typical at 7–10 years old. (4) New tyres fitted without resetting the system. (5) Wheels swapped between cars without recoding the sensors.
Real UK repair costs (2026)
Pressure top-up: free at most supermarket forecourts. Slow puncture repair (legal British Standard repair in the central tread zone): £20–£40. Valve replacement during a tyre change: £5–£15. Single TPMS sensor replacement (parts and coding): £45–£95. Set of four TPMS sensors (worth doing together if they are 8+ years old): £160–£320. TPMS coding/programming after wheel swap: £25–£60. Do not let a garage tell you a TPMS sensor reset needs a £200 specialist tool — any half-decent diagnostic kit handles it.
MOT and legal position
From January 2015 onwards, any car first used after 1 January 2012 fails its MOT if the TPMS warning is on or has been tampered with (bulb removed, system disabled, sensors disabled). The fail is a Major defect — you cannot drive away on the old certificate. If your TPMS is genuinely faulty, get it fixed before the MOT, not the day of.
How to reset the tyre pressure light (step-by-step)
Step 1: Inflate all four tyres cold to the pressures on the driver's door-jamb sticker (not the tyre wall). Step 2: Start the engine. Step 3: On most cars, drive at 25 mph or more for 10–20 minutes — the wheel-speed sensors recalibrate and the light goes out on its own. Step 4: If it stays on, you'll need to trigger a manual reset. The button is usually a small TPMS or "SET" button under the steering wheel, in the glovebox, or buried in the infotainment menu (Vehicle → Tyre Pressure → Reset / Set / Store). Hold it with the ignition on (engine off) until the dashboard light blinks twice, then release. Step 5: If the light comes back on within a day or two, a sensor battery has died or you have a slow puncture — neither will clear with a reset. The exact reset procedure varies by make, model and year — Ford, BMW, VW Group, Vauxhall and Japanese makes all do it differently. Not sure where the button is on your car? Scroll down and ask Bob below with your reg or year/make/model — he'll send the exact step-by-step reset procedure for your vehicle within 6 hours.
What the tyre pressure warning light actually means on your car
Quick summary for anyone landing on this page from a Google search of "tyre pressure warning light" or "tyre pressure light". The symbol you're looking at — usually an exclamation mark inside a horseshoe, sometimes shown as a flat tyre in cross-section — is the TPMS warning. Mandatory on every UK new car sold after November 2014. It has two behaviours you need to tell apart. Solid light means one or more tyres is measuring below the pressure threshold (typically 20–25% under the door-sticker value). Flashing light for 60–90 seconds then going solid means the TPMS system itself has a fault — usually a dead sensor battery or a sensor that's lost its coding after a wheel change. If the light comes on during a cold snap in October or November, 8 times out of 10 the fix is a two-minute top-up at the petrol station air pump. If it comes on in summer or after new tyres, it's more likely a sensor issue. Either way you cannot legally pass an MOT with a TPMS warning illuminated, so it needs sorting either way. The full step-by-step reset procedure is below, but if you want your exact make-and-model button location, drop your reg into the "Ask Bob" form at the bottom of this page and he'll send it back within 6 hours.
My TPMS light is on, but my tyres look fine. What else could it be? — Even if your tyres look okay, don't ignore the TPMS light. It could be a slow puncture you can't see, or a faulty TPMS sensor. Sensors can fail due to battery depletion (they usually last 5-10 years) or damage. A new sensor can cost £30-£80 per wheel, plus fitting and reprogramming. It's best to get it checked by a mechanic as soon as possible to avoid further issues and ensure your safety.
Is a TPMS warning light an MOT failure in the UK? — Yes, absolutely. Since 2012, a lit or malfunctioning TPMS warning light is a major defect and will result in an MOT failure. This is because it indicates a potential safety hazard relating to tyre pressure. Don't go into your MOT with the light on, as you'll just be wasting your time and money. Get it sorted beforehand, even if it's just a simple re-calibration.
Can I reset the TPMS light myself, or do I need a garage? — Sometimes you can reset it yourself after adjusting the tyre pressures. Check your car's manual for the specific procedure – it often involves a button on the dashboard or a sequence through the infotainment system. However, if the light comes back on or you can't reset it, you'll need a garage. They have specialist diagnostic tools to identify if it's a faulty sensor, wiring issue, or a more complex problem, which a DIY reset won't fix.
My TPMS light is on, but my tyres look fine. What else could it be? — Even if your tyres look okay, the TPMS light means there's a pressure issue. It could be a slow puncture you can't see, or a faulty TPMS sensor itself. These sensors are inside the wheel and can fail due to battery drain or damage. A diagnostic scan at a garage will pinpoint if it's a sensor problem or actual low pressure. Don't ignore it – low pressure wastes fuel and is dangerous.
Can I just reset the TPMS light myself, or do I need a garage? — Some cars allow a manual reset via the infotainment system or a button, usually after you've inflated the tyres to the correct pressure. However, if the light comes back on, or you can't find a reset option, then you definitely need a garage. They have specialist tools to properly diagnose and recalibrate the system, especially if a sensor needs replacing. Ignoring it means potentially driving on unsafe tyres.
Is a TPMS warning light an MOT failure in the UK? — Yes, absolutely. If your TPMS warning light is illuminated when your car goes for its MOT, it's an automatic failure. The system is a mandatory safety feature on all cars registered after 2014. It indicates a fault within the tyre pressure monitoring system, which needs to be fixed before your car can pass its MOT. Get it sorted, otherwise, it's a retest and more hassle.
Will the TPMS light fail my MOT? — Yes — on cars registered after 1 January 2012, a permanently illuminated TPMS warning is a Major MOT defect and the car will fail. Sort it before the test.
How do I reset the TPMS light after inflating my tyres? — On most cars, drive 5–10 minutes above 20 mph and it resets automatically. On BMW, Mini, Mercedes and some Vauxhalls you need to hold the TPMS reset button (often near the steering wheel) for 3 seconds, or use the dash menu — check the handbook.
Can I drive with the TPMS light on? — Short distances at low speed to reach an air pump, yes. Long motorway journeys, no — if a tyre is significantly underinflated, sidewall flex generates heat and can cause a blowout. Always check the actual pressures before you set off.
How long do TPMS sensors last? — 5–10 years, limited by the sealed internal battery. Most UK cars need their first TPMS sensor change between 7 and 9 years old. When one fails, the others are usually close behind — replacing as a set of four is often more economical.