That little tyre pressure warning light on your dashboard — the one that looks like a flat tyre with an exclamation mark — can mean a few different things. Sometimes it’s a straightforward case of a tyre being low on air. But other times, you pump everything back up, the pressures look fine on your gauge, and the light still won’t go away. Sound familiar?
If that’s the case, there’s a good chance one of your TPMS sensors has gone bad. The tricky part is figuring out which one — and that’s exactly what this article is here to help you with.
What Is a TPMS Sensor, Anyway?
Before we dive into diagnosing a faulty one, it’s worth quickly explaining what TPMS sensors actually do.
TPMS stands for Tyre Pressure Monitoring System. It’s a legal requirement on all new cars sold in the UK since November 2014, and it’s been standard on most vehicles since the mid-2000s. Each wheel has a small battery-powered sensor mounted either inside the tyre valve stem or strapped to the wheel rim. These sensors continuously (or periodically) measure the air pressure inside each tyre and transmit that data wirelessly to your car’s computer.
When pressure drops below a certain threshold — usually around 25% below the recommended level — the system triggers that warning light on your dashboard. Simple enough, in theory. But when a sensor itself stops working properly, the system can behave erratically, and that’s when diagnosis gets a bit more involved.
Signs That a TPMS Sensor Might Be Bad
The TPMS warning light doesn’t always mean a sensor is faulty — it could genuinely just be low tyre pressure. So before you assume the worst, check your tyre pressures manually with a reliable gauge. If the pressures are all within spec and the light is still on, then you’re likely dealing with a sensor issue.
Here are the most common signs that one or more TPMS sensors have gone bad:
The Warning Light Stays On Even with Correct Tyre Pressures
This is the classic tell-tale sign. You check all four tyres, they’re all properly inflated, but the dashboard light refuses to switch off. This usually means the car’s computer isn’t receiving a valid signal from at least one sensor — either because the sensor has died, its battery has run out, or it’s been damaged.
The Warning Light Blinks Before Staying Solid
Most vehicles use the TPMS light in two ways. A steady light means a tyre is genuinely low on pressure. A flashing light — typically for around 60–90 seconds before going solid — usually indicates a system fault rather than a pressure problem. If you see that blinking pattern, a faulty sensor is high on the list of suspects.
One Tyre’s Reading Is Completely Missing or Frozen
Some cars have more advanced TPMS displays that show you the individual pressure reading for each wheel — either as numbers on the infotainment screen or through a dedicated dashboard gauge. If one corner is showing “—“, “0”, or a pressure that never changes regardless of the actual tyre condition, that sensor is almost certainly faulty or dead.
Readings That Jump Around Wildly
A sensor that’s on its way out might not fail completely all at once. Instead, it can produce erratic, inconsistent readings — jumping from one value to another with no real pattern. If one tyre appears to fluctuate wildly on your display while the others remain stable, that sensor is likely struggling.
The Light Came on After a Tyre Change or Puncture Repair
TPMS sensors sit inside the wheel and can be damaged during tyre fitting if the technician isn’t careful. They can also be displaced or damaged during a puncture repair if a probe is pushed past the valve. If the warning light appeared shortly after any tyre work, there’s a reasonable chance the sensor was disturbed or damaged during the process.
A Specific Sensor Fault Code from the Vehicle
If you or a garage plugs an OBD-II diagnostic scanner into your car’s port (usually located under the dashboard, near the steering column), it may show specific fault codes related to individual TPMS sensors. Codes like C0750, C0755, C0760, or C0765 (which vary by manufacturer) often correspond to specific wheel positions. This is the most precise way to identify the faulty sensor without guesswork.
How to Pinpoint Which Sensor Is Bad
Knowing a sensor is bad is one thing. Knowing which wheel it’s on is another. Here are your main options:
Use a TPMS Diagnostic Tool
This is the most reliable method. A TPMS-specific diagnostic tool (or a professional-grade OBD scanner with TPMS functionality) can communicate directly with each individual sensor. It will attempt to read the signal from each wheel in turn and will flag any that aren’t responding.
Many garages — including mobile tyre fitting services — carry these tools. It takes just a few minutes to scan all four sensors and identify which one (or more) is causing the problem. If you’re not a DIY mechanic, this is the route we’d recommend.
Check Your Car’s In-Vehicle TPMS Display
If your car has a screen that shows individual tyre pressures for each wheel, take a careful look at the readings. Inflate all tyres to the correct pressure (check your door sill label or owner’s manual for the spec), reset the TPMS system as described in your manual, and then watch the display closely over the next few minutes or the next drive.
- If one corner shows no reading or a clearly wrong value, that’s your suspect wheel.
- If all four show readings but one seems “stuck” or doesn’t change when you adjust the pressure, that’s also a red flag.
The Process of Elimination Method
If you don’t have access to a diagnostic tool and your car doesn’t show individual pressure readings, you can try a more manual approach — though it’s less reliable.
Check each tyre’s pressure with a separate handheld gauge. Then compare those readings to whatever the car’s system shows (if it shows anything at all). Any significant discrepancy between what the car thinks and what you’re measuring manually points toward a sensor on that specific wheel.
This method works better on vehicles that do show individual readings, but it’s better than nothing if you’re stuck without specialist equipment.
Ask a Garage to Read the Sensor IDs
Every TPMS sensor has a unique ID that the vehicle’s computer stores. A garage with the right software can pull up a list of stored sensor IDs and compare them to the sensors that are actively transmitting. Any sensor that isn’t transmitting its ID — or is transmitting a weak or corrupted signal — will stand out as the problem unit.
Why TPMS Sensors Go Bad
It’s worth understanding the common reasons sensors fail, especially if you’re trying to decide whether to repair or replace:
Battery Failure
This is by far the most common cause. TPMS sensors run on small lithium batteries that are permanently sealed inside the sensor housing. They typically last 5–10 years or 100,000 miles. Once the battery dies, that’s it — the whole sensor needs replacing. There’s no way to swap just the battery.
Physical Damage
Sensors can be cracked or broken by kerb impacts, pothole strikes, or rough handling during tyre changes. If your car’s been through a significant wheel impact recently, sensor damage is worth considering.
Corrosion
The valve stem area is exposed to moisture, road salt, and grime. Over time, corrosion can eat into the sensor housing or valve, causing leaks or communication failures.
Signal Interference
Rare, but it happens. In some areas, radio frequency interference can disrupt the sensor signal temporarily. This usually isn’t a persistent issue, but it can cause intermittent warnings.
Wrong Sensor After a Tyre Change
If you’ve had new tyres fitted and the technician replaced sensors at the same time, there’s a chance the wrong type was installed, or the new sensors weren’t properly programmed to the car. The vehicle’s computer needs to “learn” each sensor’s unique ID — if that programming step was skipped, the light will stay on.
What Happens If You Ignore a Faulty TPMS Sensor?
The honest answer: in the short term, probably not a lot — if your actual tyre pressures are fine. TPMS is a warning system, not a safety mechanism that actively controls your tyres.
However, ignoring the warning is risky for a couple of reasons:
- You lose your early warning system. The whole point of TPMS is to alert you when a tyre is losing pressure — potentially before you’d notice by handling or feel. A faulty sensor leaves you flying blind on that wheel. If that tyre develops a slow puncture, you won’t get a warning until it’s very flat indeed.
- It will likely fail your MOT. In the UK, a TPMS malfunction indicator that’s permanently illuminated is a reason for an MOT advisory, and in some cases a failure, depending on the vehicle and tester. It’s worth getting it sorted before your next test.
- The warning light becomes meaningless. If the TPMS light is always on because of a faulty sensor, you’ll start ignoring it entirely — which means you’ll also ignore it if a genuinely low tyre triggers it in future. That’s a bad habit to get into.
Can You Drive with a Bad TPMS Sensor?
Technically, yes — as long as your tyres are all correctly inflated, a faulty sensor doesn’t make the vehicle unsafe to drive. But as mentioned above, you’re losing your pressure early-warning capability on that corner of the car.
Our advice: get it checked and sorted sooner rather than later. TPMS sensor replacement is usually a straightforward job, especially for a mobile tyre fitting service that can come to you at home or at work.
How to Reset the TPMS Light After a Sensor Fix
Once a faulty sensor has been replaced and programmed, the TPMS light should go off on its own — but it sometimes needs a little help. Here’s the usual process:
- Make sure all four tyres are inflated to the correct pressure as specified in your vehicle handbook or door sill sticker.
- Find the TPMS reset button — on many vehicles it’s located under the steering column, in the glovebox, or accessible via the infotainment menu. Your owner’s manual will tell you where it is.
- Hold the reset button (if applicable) until the TPMS light blinks three times, then release it.
- Drive the car for a few minutes at above 25 mph. The sensors need to transmit a few signals before the system confirms everything is working correctly.
On some vehicles, particularly those where sensors have been replaced, the car may need to go through a “sensor relearn” procedure — sometimes done with a scan tool, and sometimes done via a specific driving routine. Your fitting technician should handle this as part of the sensor replacement job.
How Much Does TPMS Sensor Replacement Cost in the UK?
Costs vary depending on your vehicle make, the type of sensor it uses, and who does the work, but as a rough guide:
- Budget aftermarket sensors: £20–£40 per sensor (parts only)
- OEM/manufacturer sensors: £40–£100+ per sensor
- Labour and programming: Typically £20–£50 per sensor at a garage
- Mobile fitting service: Often comparable or slightly more convenient, with the added benefit of no travel or waiting time
On average, most drivers pay somewhere between £50 and £150 all-in per sensor for supply and fitting. If multiple sensors need replacing at once, many garages will offer a small discount on the labour.
It’s worth noting that if your car uses “indirect TPMS” (which calculates tyre pressure from wheel speed sensors rather than dedicated pressure sensors), there are no physical sensors to replace — in that case, the fault lies elsewhere in the system.
Should You Replace All Four Sensors at Once?
This is a question we get asked a lot, and honestly, there’s no single right answer.
If one sensor has failed due to a dead battery and your other three are around the same age (say, 7–9 years), it’s not a bad idea to replace all four at the same time. You’ll likely be back within 12–18 months to do the others anyway, and replacing them as a set saves on multiple labour charges.
On the other hand, if the failure was due to physical damage (a kerb strike, for example) rather than age-related battery death, and the other sensors are only a few years old, replacing just the damaged one is perfectly reasonable.
Ask your technician for their opinion based on the age and condition of your existing sensors — a good one will give you an honest answer rather than just trying to upsell you.
Final Thoughts
A bad TPMS sensor is one of those jobs that’s easy to put off, but it’s really worth getting on top of relatively quickly. Identifying which sensor is faulty doesn’t have to be complicated — a proper diagnostic scan will pinpoint the problem in minutes, and the fix is usually straightforward.
If you’re unsure whether your TPMS warning is a genuine pressure issue or a sensor fault, start by checking your tyre pressures manually. If everything’s topped up and the light stays on, or if you’re seeing that characteristic flashing pattern, get in touch with a tyre specialist who can carry out a sensor scan and advise on next steps.
And if your car is overdue for a tyre check, a TPMS diagnostic, or sensor replacement — we’re here to help, coming to you wherever your car is parked.
Frequently Asked Questions
How do I know if it’s a bad TPMS sensor or just low tyre pressure?
Check all four tyres manually with a handheld pressure gauge. If the pressures are all correct and the TPMS warning light is still on, or if the light is flashing before staying solid, it’s more likely a sensor fault than a pressure issue. Genuinely low pressure usually causes a steady light that goes off once you’ve inflated the tyre.
Can I find out which specific wheel has the faulty sensor without going to a garage?
If your car has an infotainment display that shows individual tyre pressures per wheel, you may be able to spot a missing or frozen reading yourself. However, the most reliable way is a TPMS diagnostic scan, which most tyre fitting professionals and garages can carry out quickly and inexpensively. Without a tool, it can be difficult to pinpoint the exact wheel.
What does it mean when the TPMS light flashes instead of staying solid?
A flashing TPMS light — typically blinking for around 60–90 seconds before going solid — is your car’s way of signalling a system fault rather than just low pressure. It usually means one or more sensors aren’t communicating with the vehicle’s computer properly. This is a strong indicator of a faulty or dead sensor.
How long do TPMS sensors last?
Most TPMS sensors last between 5 and 10 years, or around 100,000 miles — whichever comes first. The limiting factor is the internal battery, which is sealed inside the sensor and can’t be replaced separately. Once it dies, the whole sensor unit needs to be replaced.
Will a faulty TPMS sensor cause my car to fail its MOT?
It can, yes. In the UK, a TPMS malfunction warning light that is permanently illuminated is considered a defect under MOT testing rules for vehicles that were originally fitted with TPMS from the factory. Depending on the tester and vehicle, this can result in an advisory or an outright failure. It’s worth getting it sorted before your test.
Can I still drive safely with a bad TPMS sensor?
You can drive with a faulty sensor as long as your actual tyre pressures are correct — the sensor failure itself doesn’t make the car mechanically unsafe. The real risk is that you lose your automatic early warning for that wheel. If that tyre develops a slow puncture, you won’t get an alert until it’s significantly underinflated. We’d recommend getting it fixed sooner rather than later for that reason.
My TPMS light came on after a tyre change. Could the garage have damaged the sensor?
Yes, unfortunately this does happen. TPMS sensors sit inside the wheel and can be cracked or dislodged during the tyre fitting process if care isn’t taken. It’s also possible that a replacement sensor was fitted but wasn’t properly programmed to the vehicle — the car needs to “learn” each sensor’s unique ID, and if that step was skipped, the warning light will stay on. Contact the garage that did the work and ask them to check.
How much does it cost to replace a TPMS sensor in the UK?
As a rough guide, expect to pay between £50 and £150 per sensor all-in for parts, fitting, and programming. Budget aftermarket sensors tend to cost less; OEM manufacturer sensors cost more. Labour and programming typically adds £20–£50 on top of the parts price. If you’re replacing multiple sensors at the same time, many garages will discount the labour.
Do I need to replace all four TPMS sensors at once?
Not necessarily. If the failure was caused by physical damage (like a kerb strike) and your other sensors are relatively new, replacing just the damaged one is fine. However, if the failure is age-related — a dead battery after 7–9 years — and your other sensors are a similar age, it often makes financial sense to replace all four at once and save on multiple call-out or labour charges down the line. Ask your technician what they’d recommend based on the age of your sensors.
Can a TPMS sensor be repaired, or does it always need replacing?
In almost all cases, a faulty TPMS sensor needs to be replaced entirely. The battery inside is permanently sealed, so it can’t be swapped out. If the sensor has been physically damaged, repair isn’t a practical option either. The valve core and cap can sometimes be replaced separately if that’s the source of a minor leak, but the sensor unit itself is generally treated as a non-serviceable component.
How do I reset the TPMS light after a sensor has been replaced?
First, make sure all four tyres are inflated to the pressures specified in your owner’s manual or door sill sticker. Then locate the TPMS reset button (usually under the steering column or in the glovebox — check your manual). Hold it until the warning light blinks three times, then drive the car for a few minutes above 25 mph. On some vehicles, a technician needs to perform a “sensor relearn” procedure using a scan tool — this is especially common after sensor replacements and should be included as part of the fitting job.
My car shows individual tyre pressures on the screen. One wheel says 0 or “—“. Is that definitely a bad sensor?
Almost certainly yes. If one corner of your display is showing zero, dashes, or a reading that never changes regardless of the actual tyre pressure, that sensor has either lost its battery charge or stopped transmitting. A diagnostic scan will confirm it, and a replacement sensor will need to be fitted and programmed.
Are TPMS sensors specific to my car, or are they universal?
There are broadly two types — OEM sensors (made specifically for your vehicle by the manufacturer) and aftermarket “programmable” or “multi-application” sensors that can be configured to work with a wide range of vehicles. Both can work well, but the sensor needs to be compatible with your car’s frequency and protocol, and it must be programmed with the correct settings before it’ll communicate with your vehicle. This is another reason why proper programming after fitting is so important.
