Does a tyre pressure light fail an MOT?

It depends what the lamp is telling you, and this is the single most misunderstood point about the rule. A tyre pressure monitoring system that is malfunctioning or obviously inoperative is a major defect on cars first used on or after 1 January 2012, with 97,515 recorded failures in the DVSA data behind this site. But the defect is about the system being broken, not about a tyre being soft. If the lamp is on because a tyre genuinely is under-inflated, inflating it correctly clears the warning and there is nothing to fail. If it is on because a sensor has died and the system can no longer monitor anything, that is the failure. Cars first used before 1 January 2012 are not failed on this.

How long do TPMS sensor batteries last?

Typically seven to ten years, depending on how much the car is driven, since the sensors transmit more often when the wheels are turning. The battery is sealed inside the sensor and cannot be replaced on its own, so a flat battery means a new sensor. Because all four are usually the same age and have done the same mileage, when one fails the others are generally close behind, which is why replacing them as a set is often better value than paying for four separate tyre removals over the following couple of years.

Why did my TPMS light come on after fitting winter wheels?

Almost certainly because the new wheels' sensors have not been registered to the car, or because those wheels have no sensors in them. Each sensor transmits a unique identity, and the receiving module only listens to identities it has been told belong to the vehicle. Swap to a second set of wheels and the module hears identities it does not recognise and stops hearing the ones it expects. Most cars need a relearn procedure, done with a scan tool or a specific sequence from the handbook, each time the wheels are swapped.

Can I replace a TPMS sensor myself?

Not realistically, because the sensor lives inside the wheel and the tyre has to come off to reach it. That means a tyre machine and a balance afterwards, so it is a job for a tyre fitter. What you can usefully do is ask them to fit a service kit — new valve core, seal, nut and cap — at the same time, because corrosion at the valve stem is one of the main reasons these sensors fail, and to relearn the sensor identities to the car before you leave.

Chassis code · standard

C0950Front left tyre pressure sensor not reporting

Standard definition: Tyre Pressure Monitoring Sensor Front Left

Last updated 27 July 2026

Quick answer

The tyre pressure monitoring system has stopped hearing from the sensor in the front left wheel. The tyre may be perfectly well inflated; what has failed is the system's ability to tell you about it, and that distinction matters at MOT time.

How the car works this out

A direct tyre pressure monitoring system has a small battery-powered sensor inside each wheel that measures pressure and temperature and transmits them by radio every few seconds or minutes, each with its own unique identity. The receiving module knows which identities belong to the car and expects to hear from all of them. C0950 is set when the front left sensor stops transmitting, transmits an implausible value, or reports that its own battery is failing. There is a second kind of system, called indirect, which has no sensors at all and infers a soft tyre from the wheel speed sensors; a car with that arrangement cannot set this code.

What you might notice

Tyre pressure warning lamp on, often flashing for around a minute at start-up before staying steady
One corner showing dashes, blanks or no pressure on the dashboard display
The system unable to be reset no matter how carefully the tyres are inflated
Warnings appearing after a wheel change or a switch to winter wheels
Everything otherwise normal, with correctly inflated tyres

What causes it

Most likely first. A code names the check that failed, not the part that failed it, so more than one of these can produce the same number.

1The sensor's internal battery reaching the end of its life, typically after seven to ten yearsCommon
How to check: A TPMS trigger tool wakes each sensor and reports its identity, pressure, temperature and battery condition. It is the definitive test and takes a tyre fitter moments per wheel. If one sensor is at end of life, the others are usually the same age.
2A sensor damaged during tyre fitting, which is easily done if the fitter is not looking for itCommon
How to check: Ask whether the fault appeared immediately after a tyre change. The timing is usually conclusive.
3A corroded aluminium valve stem, which can seize to the steel core and snap off, taking the sensor with itCommon
How to check: Inspect the valve stem for white powdery corrosion where the two metals meet. Service kits with new valve cores, seals and caps are cheap and should be fitted at every tyre change.
4Sensor identities not relearned after a wheel change, a tyre rotation or a swap to a second set of wheelsCommon
How to check: Ask whether the sensors were registered to the car after the last wheel change. Many cars need a scan tool or a specific relearn procedure and will not find them on their own.
5A replacement wheel or a space-saver spare with no sensor fitted at allPossible
6Radio interference, or a fault in the receiver or its aerialLess common

What to do about it

1Check and correct all four tyre pressures with a gauge you trust before assuming the system is broken. Cold pressures against the figures on the door pillar or filler flap, and do not forget the spare on cars that monitor it.
2Have the sensors read with a TPMS trigger tool. It identifies which sensor is silent and reports the battery condition of the others, which tells you whether you are about to have the same conversation three more times.
3Ask for the sensor identities to be relearned if the wheels have been changed, rotated or swapped for a winter set.
4Have service kits fitted whenever tyres are changed. New valve cores, seals and caps are inexpensive and prevent the corrosion that destroys these sensors.
5Consider replacing sensors as a set if they are all of a similar age and one has died of battery exhaustion, because the others will follow within a year or two and each visit costs a tyre removal.

Can you keep driving?

Yes

Nothing about the car's braking, steering or handling is affected, and if the tyres are correctly inflated you are as safe as you were before. What you have lost is early warning of a slow puncture, so check the pressures manually with a gauge every couple of weeks until it is fixed. That is what everybody did before these systems existed, and it works.

Will it fail an MOT?

This is a major defect with an important condition attached. A tyre pressure monitoring system that is malfunctioning or obviously inoperative is a major defect on cars first used on or after 1 January 2012, and 97,515 failures have been recorded against it in the DVSA data behind this site, ahead of the braking and airbag lamps. The nuance that catches people out is what triggers it: the car fails because the system itself is faulty, not because a tyre happens to be soft. A lamp showing low pressure is telling you to put air in; a lamp showing a system fault is telling you the monitoring has stopped working, and only the second is the defect. Cars first used before 1 January 2012 are not failed on this at all, even if they have the system fitted.

The light this turns on

Tyre pressure monitoring system fault lightThe monitoring system itself has failed, rather than a tyre being soft. On most cars it uses the same symbol as the ordinary tyre pressure warning but announces itself differently: it flashes for around a minute after you switch on and then stays on steadily. That behaviour is the single most useful thing to know here, because it is also exactly what the MOT tester looks for.

Common questions

Does a tyre pressure light fail an MOT?: It depends what the lamp is telling you, and this is the single most misunderstood point about the rule. A tyre pressure monitoring system that is malfunctioning or obviously inoperative is a major defect on cars first used on or after 1 January 2012, with 97,515 recorded failures in the DVSA data behind this site. But the defect is about the system being broken, not about a tyre being soft. If the lamp is on because a tyre genuinely is under-inflated, inflating it correctly clears the warning and there is nothing to fail. If it is on because a sensor has died and the system can no longer monitor anything, that is the failure. Cars first used before 1 January 2012 are not failed on this.
How long do TPMS sensor batteries last?: Typically seven to ten years, depending on how much the car is driven, since the sensors transmit more often when the wheels are turning. The battery is sealed inside the sensor and cannot be replaced on its own, so a flat battery means a new sensor. Because all four are usually the same age and have done the same mileage, when one fails the others are generally close behind, which is why replacing them as a set is often better value than paying for four separate tyre removals over the following couple of years.
Why did my TPMS light come on after fitting winter wheels?: Almost certainly because the new wheels' sensors have not been registered to the car, or because those wheels have no sensors in them. Each sensor transmits a unique identity, and the receiving module only listens to identities it has been told belong to the vehicle. Swap to a second set of wheels and the module hears identities it does not recognise and stops hearing the ones it expects. Most cars need a relearn procedure, done with a scan tool or a specific sequence from the handbook, each time the wheels are swapped.
Can I replace a TPMS sensor myself?: Not realistically, because the sensor lives inside the wheel and the tyre has to come off to reach it. That means a tyre machine and a balance afterwards, so it is a job for a tyre fitter. What you can usefully do is ask them to fit a service kit — new valve core, seal, nut and cap — at the same time, because corrosion at the valve stem is one of the main reasons these sensors fail, and to relearn the sensor identities to the car before you leave.

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