Key takeaways
- A TPMS sensor sits in each wheel and reports tyre pressure to the car; the battery is sealed in and lasts roughly 5 to 10 years.
- When a sensor fails, the dashboard warning light stays on, and on cars first used from 2012 that is an MOT failure.
- Replacing one sensor is usually a modest part cost plus fitting, and it is most economical done while the tyre is already off.
- Direct systems use a sensor in each wheel; indirect systems use the ABS wheel speed sensors and have nothing to replace.
- A failed sensor cannot be repaired because the battery is sealed; the whole sensor unit is renewed.
The tyre pressure warning light is easy to ignore until MOT time, when a failed sensor can fail the test outright. Tyre pressure monitoring sensors do not last forever, and when one dies it needs replacing rather than mending. This guide explains how the system works, what a replacement involves, what it typically costs, and why it is cheapest to sort while the tyre is already off the wheel.
How does a TPMS sensor work?
A TPMS sensor measures the air pressure inside each tyre and sends it wirelessly to the car, which warns you when a tyre drops too low. On a direct system there is a small battery-powered sensor built into each wheel, usually as part of the valve. When pressure falls below a set point, the dashboard light comes on.
The sensor is sealed, including its battery, so nothing can be charged or serviced. That sealed design is why a flat sensor battery means a whole new sensor. Most last between 5 and 10 years, so they often start failing around the same age you are replacing tyres anyway, which makes the timing convenient.
What are the signs of a failing TPMS sensor?
The clearest sign is a tyre pressure warning light that stays on or flashes even when all your tyres are correctly inflated. A failing sensor may also give false low-pressure alerts, or the light may glow steadily after a battery dies. The TPMS warning is an MOT failure on cars first used from 2012, so it cannot be ignored.
It helps to rule out the simple cause first. If a tyre really is low, top it up and see whether the light clears. If pressures are correct and the light stays on, suspect a sensor, a flat sensor battery or a damaged valve. Our guide on why your tyre pressure light is on walks through the causes in detail.
How much does TPMS sensor replacement cost?
Replacing a single TPMS sensor usually means a modest part cost plus the labour to fit it, and it is far cheaper done while the tyre is already off the wheel for another reason. Aftermarket sensors are generally less expensive than genuine manufacturer parts, and a fitter programmes the new sensor so the car recognises it.
Costs vary with the car and the sensor type, so the figures below are a guide rather than a fixed price. The big saving comes from timing: pairing the job with a tyre change avoids paying twice to break the tyre down. The table shows what tends to drive the price up or down.
| Factor | Effect on cost |
|---|---|
| Genuine vs aftermarket sensor | Genuine parts usually cost more |
| Done with a tyre change | Cheapest, as the tyre is already off |
| Done on its own | Adds the cost of breaking the tyre down |
| One sensor vs all four | All four costs more but evens out sensor age |
| Programming and a new valve service kit | Small extra, but worth doing properly |
Can a TPMS sensor be repaired instead of replaced?
No, the sensor itself cannot be repaired, because its battery is sealed inside and cannot be replaced. Once the battery is flat or the electronics fail, the whole sensor unit is renewed. What can be serviced is the valve part: the rubber seal, nut and core, which are often refreshed with a service kit at each tyre change.
This is an important distinction. If your light is on because of a damaged valve or a loose core, that may be a cheap fix without a new sensor. If the sensor electronics or battery have failed, replacement is the only option. A fitter can diagnose which it is with a TPMS tool before quoting.
Should you replace one sensor or all four?
You can replace just the failed sensor, and for a one-off failure that is the sensible, cheaper choice. But because all four sensors are usually the same age, when one battery dies the others may not be far behind. If your sensors are old and you are already paying for fitting, doing all four can save repeat visits.
There is no hard rule, so weigh the cost against the age of the system. A two or three-year-old car with one damaged sensor needs only that one. An older car on its original sensors, where one has died of old age, is a reasonable case for replacing the set. A fitter can read each sensor's health and advise.
Getting a sensor replaced without the garage trip
Because a TPMS sensor sits inside the wheel, replacing it means breaking the tyre down from the rim, which is exactly what mobile fitting equipment does at your door. That makes it easy to pair with a tyre change or to sort on its own before an MOT. For related reading, see how to check your tyre pressure so you can rule out a genuinely low tyre first. When a sensor has failed, Fast Tyre can supply, fit and programme a new one through our TPMS replacement service at your home, work or roadside across London and central England.
Frequently asked questions
Expect a modest part cost plus fitting per sensor, with aftermarket sensors cheaper than genuine ones. It is far cheaper done while the tyre is already off for a tyre change. Doing it on its own adds the cost of breaking the tyre down from the rim.
No. The battery is sealed inside the sensor and cannot be changed, so once it is flat the whole sensor unit is renewed. The valve parts, such as the seal, nut and core, can be serviced with a kit, but the sensor electronics and battery cannot be repaired.
Yes, on cars first used from 2012 a TPMS warning light staying on is an MOT failure. The tester checks the light works and goes out as expected. A dead sensor that keeps the light lit means a fail, so it is worth fixing before your test.
Most TPMS sensors last between 5 and 10 years, limited by their sealed internal battery. They often start failing around the same age you are replacing tyres, so renewing a dead sensor during a tyre change is the most economical time to do it.
No, you can replace just the failed one. But because all four are usually the same age, when one dies the others may follow soon. If the system is old and you are already paying for fitting, doing all four can save repeat visits and even out their age.
You can drive, but you should not ignore it. First check your pressures, as the light may be warning of a genuinely soft tyre. If pressures are fine and the light stays on, a sensor has likely failed, which needs fixing before your MOT and to restore the warning.