A small amber symbol has just appeared on your dashboard, a horseshoe shape with an exclamation mark inside. You do not know if it means a flat tyre, a system fault, or just cold weather. The car feels fine, you are still driving, and you are trying to decide whether to pull over or carry on.
The TPMS light is one of the most common dashboard warnings in UK cars, and one of the most misunderstood.
The same symbol can mean a real flat, a slow leak, a sensor fault, or a cold-morning false alarm. The right response depends on which.
Short version: if the light is solid, you most likely have low pressure in at least one tyre, so check and top up. If it flashes for 60 to 90 seconds then stays on, the TPMS itself has a fault, usually a dead sensor. Here is how to tell the difference and what to do next.
Solid light vs flashing light: what each one means
This single distinction tells you most of what you need to know, so start here.
Solid, constant light
This means at least one tyre is significantly under or over inflated. The usual trigger is pressure dropping around 25% below spec, roughly 6 to 7 PSI low.
The most common cause is a slow loss of air over weeks, from a tired seal, a leaky valve, or a kerb-damaged sensor seat. Action: check your pressures with a gauge as soon as you can safely stop.
Flashing light, then solid
This means the TPMS system has a fault, usually a failed sensor, a dead sensor battery, or a communication problem. It flashes for 60 to 90 seconds on start-up, then stays on.
In this state the system is not monitoring your tyres, so you have to check them manually. Action: get to a fitter, or call us to come to you, for a diagnosis.
Light that comes on and off
This means a tyre is hovering right at the warning threshold. Small temperature swings push it over and back.
It is most common in autumn and winter, when overnight cold drops the pressure and daytime warmth brings it back. Action: top all tyres to spec. If it keeps returning, you have a slow leak.
Not sure which one yours is? WhatsApp a photo of your dashboard to wa.me/447955533000 and we will tell you.
Quick answer: what to do in the next 10 minutes
- Do not panic. The light is not always an emergency.
- Notice the pattern, solid, flashing, or intermittent.
- Ease off the speed and avoid hard braking or cornering.
- If the car feels normal and the light is solid, drive carefully to somewhere you can check the tyres.
- If the car feels wrong, with vibration, pulling, or drag, pull over now. You may have a real flat.
- Check all four tyres by eye for anything clearly low or going down.
- Check pressures with a gauge at the next safe stop, a fuel station, home, or work.
- Top up to spec, found on the sticker in the driver’s door jamb or the fuel filler flap.
If a tyre is actually flat, our guides to a flat on the motorway or a breakdown at night take over from here.
7 reasons the light just came on
The same symbol has several causes. Run down these and you will usually spot yours.
1. Cold weather, the most common false alarm
Pressure drops about 1 PSI for every 5 degrees Celsius the temperature falls. A tyre at 32 PSI in summer can read around 28 on a frosty Glasgow morning.
If you were already at the lower end of spec, the cold tips you over. Fix: top up to spec when cold, and the light should clear after 10 to 20 minutes of driving.
2. A slow puncture you have not noticed
A nail or screw too small to feel can let air out slowly over hours or days. The TPMS catches it before your eyes would. Fix: check the tread for embedded objects, and have a fitter inspect and repair if needed. Our guide to a nail or screw in a tyre explains when it can be repaired.
3. A bead seat leak, often from an old kerb hit
Damage to the wheel edge where it seals against the tyre can let air past, often weeks or months after the original kerb scuff. Fix: remove the tyre, clean the corrosion off the bead seat, and re-seal. Our guide to kerbed wheels covers how this happens.
4. The sensor battery has died
Sensors are sealed units with batteries that cannot be replaced, lasting around 5 to 10 years. A lot of UK cars are now reaching that age, so failures are climbing. Fix: a replacement sensor coded to your car.
5. The sensor is physically damaged
Kerb hits, pothole impacts, or rough tyre fitting can damage the in-wheel sensor, and old ammonia-based sealants can corrode it. Fix: a replacement sensor. Our guides to pothole damage and a sealant kit that will not work cover the causes.
6. New wheels or tyres fitted without a relearn
After a tyre change, rotation, or wheel swap, some cars need a relearn procedure to re-pair the sensors to the right positions. It is common after fitting aftermarket alloys. Fix: run the car’s relearn procedure, or have a fitter trigger it with a tool.
7. A valve stem leak
The valve you fill the tyre through can develop a slow leak after years of use, especially the aluminium stems used in some TPMS systems. Fix: a replacement valve stem, usually done as part of any tyre change.
Can you drive with the TPMS light on?
Here is the honest decision, both ways.
Yes, with care, if:
- You have manually checked all four tyres and they are at the correct pressure
- The car drives normally, with no vibration, pulling, or drag
- You are heading straight to a fitter or home
- It is a system fault (flashing then solid) rather than a real flat
No, pull over now, if:
- You can feel a tyre is wrong
- You can see a tyre is low or going down
- The handling has changed since the light came on
- You hear hissing from a wheel
The legal position
It is not illegal to drive with the light on. But you are legally responsible for keeping the car roadworthy. If the light is on because of a genuine safety issue and you keep driving, the car is unroadworthy, and that can become a driving-in-dangerous-condition offence, up to £2,500 and 3 penalty points.
TPMS and the MOT: what you need to know
This catches a lot of people out, so it is worth being precise.
For cars first registered on or after 1 January 2012, the TPMS must be working. A visible TPMS warning light at the test is a guaranteed fail, whether the cause is a real low tyre or a system fault. You can read the official position in the DVSA MOT inspection rules.
To avoid a needless failure, check the dashboard before the test, fix the underlying cause first, and if a sensor needs replacing, do it at least a week ahead to allow for the relearn. Aftermarket wheels fitted with no sensors will fail automatically, and a sensor with a dying battery may scrape through one year and fail the next.
Direct vs Indirect TPMS: why it matters
Knowing which system your car has changes how the fault gets diagnosed.
Direct TPMS uses a small battery-powered sensor inside each wheel that measures actual pressure. It can tell you which specific tyre is low, sometimes with an exact PSI per wheel. It is used in most premium cars and increasingly across mainstream models.
Indirect TPMS uses the ABS wheel-speed sensors to spot when one tyre rotates differently from the others. There is no sensor inside the wheel, so it tells you something is wrong but not which tyre or by how much. It is common in smaller and cheaper cars.
In practice, a direct system fault usually means a sensor replacement, which we can do at the scene with a programmer. An indirect fault usually just needs a software recalibration after re-inflating. Either way, if there is a real low tyre, the response is the same: top up the right one, recheck, then reset.
How to reset your TPMS light
There are three common methods. Always confirm your pressures are correct first.
Drive to recalibrate. Top up all tyres to spec when cold, then drive at a steady 25 to 50 mph for 10 to 20 minutes. The system relearns and the light goes off.
Reset button. Some cars have a physical button under the steering wheel or in the glovebox. Hold it with the ignition on until the light flashes three times, then drive a few minutes to confirm.
Infotainment menu. Many modern cars from BMW, Mercedes, Audi, the VW group, and Hyundai or Kia reset through a Tyre Pressure or TPMS option in the settings menu.
If the light will not reset, the usual reason is that a tyre genuinely is still low and you missed one. Less often, a sensor is dead and needs replacing. Rarely, it is a software fault that needs dealer diagnosis.
Cost of TPMS sensor replacement: honest UK pricing
Treat these as typical ranges and always ask for the total per-wheel price before any work starts.
| Service | Typical UK cost | Notes |
| Diagnostic check | £20 to £40 | Some fitters fold this into the repair |
| Single sensor replacement | £30 to £80 per sensor | Plus fitting and programming |
| Sensor programming or cloning | £15 to £40 | Needed for a new sensor to be recognised |
| Full per-wheel swap (parts, labour, coding) | £50 to £150 | Total per wheel, varies by car |
| TPMS relearn after a tyre change | £15 to £30 | Sometimes free as part of a fit |
| Valve stem replacement | £15 to £30 each | Usually done with a sensor swap |
Premium German cars and some EVs sit at the higher end, while mainstream brands like Ford, Vauxhall, Hyundai, Kia, and Toyota tend to be lower.
We could push a £150 sensor replacement on every callout. We do not. Most often the real issue is a kerb-damaged bead seat, a cold-morning false alarm, or a slow valve leak. We diagnose first and replace only when it is genuinely needed.
Diagnosis at your driveway, no garage queue, with honest pricing before any work starts.
Why mobile fitting works well for TPMS
Replacing a sensor means taking the tyre off the wheel, swapping the sensor inside, refitting, balancing, and programming. All of that can happen on your driveway or in a work car park.
There is no need to lose time to a garage queue. We diagnose first, so if it is just a bead-seat leak we re-seal rather than sell you a sensor you do not need. Our 30 to 45 minute Scotland-wide arrival means same-day diagnosis even if the light came on while you were at work.
Need us nearby? See our pages for Glasgow, Edinburgh, Aberdeen, Dundee, and Inverness.
Why TPMS lights peak on Scottish winter mornings
There is a simple reason your light loves a frosty start.
Pressure falls about 1 PSI for every 5 degrees the temperature drops. Glasgow can swing from a 10 degree autumn afternoon to minus 2 on a clear winter morning, a 12 degree drop and roughly 2 to 3 PSI lost. Highland mornings can be colder still.
If your tyres are already at the bottom of spec, the cold pushes you over the threshold before breakfast. Top them up in autumn before the first frosts, and aim for the higher end of the recommended range. If the light comes on cold and clears after 10 to 20 minutes, that is the cold cycle. If it returns the next cold morning on the same wheel, you have a slow leak, not just cold.
A real callout pattern we attend most weeks
We do not need to invent this one.
A driver on Glasgow’s Southside sees the TPMS light on a cold January morning. They top up at the garage, the light goes off, then it comes back two days later on the same wheel. By the time they call us, they have topped up three times in a week.
Our diagnosis on arrival was a kerb-damaged bead seat on the front left, from a knock the driver had forgotten about months earlier.
We removed the tyre, cleaned the corroded bead seat, re-sealed it, refitted, and tested. The whole job took around 35 minutes, and the light has stayed off since. If your light keeps returning on one wheel, our guide to one tyre that keeps losing pressure goes deeper.
Frequently asked questions
What does the TPMS warning light mean?
It means your tyre pressure monitoring system has detected something. A solid light usually means at least one tyre is under-inflated, around 25% below spec. A flashing light that then stays on means the TPMS itself has a fault, typically a dead sensor.
Can I drive with the TPMS light on?
Yes, if you have manually confirmed all tyres are at the correct pressure and the car drives normally. No, if you can feel something wrong, see a tyre going down, or hear hissing. It is not illegal, but you remain responsible for the car being roadworthy.
Why does my TPMS light come on in cold weather?
Cold air takes up less space, so a drop of about 5 degrees reduces pressure by roughly 1 PSI. If your tyres sit at the lower end of spec, a cold Scottish morning can push them under the threshold. Top up to the higher end of the range in autumn.
How do I reset my TPMS warning light?
Top all tyres up to the manufacturer’s spec, then either drive 10 to 20 minutes at a steady speed to auto-recalibrate, press the TPMS reset button, or run the reset through your dashboard menu. Confirm the pressures are correct before resetting.
Will the TPMS light cause an MOT failure?
Yes, for cars first registered on or after 1 January 2012. A visible warning light at the test is a guaranteed fail, whether the cause is a low tyre or a sensor fault. Fix the underlying issue at least a week before the MOT to allow for a relearn.
How much does it cost to replace a TPMS sensor in the UK?
Typically £50 to £150 per wheel, including the sensor at £30 to £80, plus labour and programming. Premium German cars and EVs sit higher, mainstream brands lower. Always ask for the total per-wheel price upfront.
How long do TPMS sensors last?
Usually 5 to 10 years. The sensors are sealed units with batteries that cannot be replaced. Many UK cars are now reaching that age, which is why sensor failures are becoming more common.
Can sealant damage my TPMS sensor?
Factory-issued kits supplied with your car are generally safe. Older or aftermarket ammonia-based sealants can damage the sensor. Use the kit that came with your vehicle where you can.
Do I need a TPMS sensor in my spare wheel?
Most space-saver spares do not have one, so the system will not monitor them. If you have a full-size spare with a sensor, it needs the matched ID code programmed to your car. Some premium models include this as standard.
If your TPMS light is on right now, here’s what to do
You spotted it, the car feels fine, and you are working out the next step. That is the right instinct.
- Note the pattern, solid, flashing, or intermittent
- Top up all four tyres to spec at the nearest safe stop
- If the light will not clear or returns the next day, call us on 07955 533000
- WhatsApp your location: wa.me/447955533000
- Sensor diagnosis and replacement on your driveway or at work, no garage queue
- Average arrival 30 to 45 minutes across Scotland, 24/7
A TPMS light is rarely a crisis. It is just your car asking you to check something. Let us help you find out what.
