The TPMS light is one of the more misunderstood symbols on a dashboard. The shape rarely makes its meaning obvious, and it actually signals two different things depending on how it behaves. Telling them apart is the key to knowing what to do.
The symbol
The standard warning is an amber symbol shaped like a cross-section of a tyre, a horseshoe or open bracket sitting on a flat base, with an exclamation mark in the centre. It is easy to mistake for a brake or fluid warning at a glance. Some cars skip the symbol and instead show a small diagram of the car with a pressure figure against each tyre, or simply the words "tyre pressure low".
Steady light: a tyre is low
A light that comes on and stays on means the system has detected at least one tyre below its threshold, usually around a quarter under the recommended pressure. The common causes are:
- A slow puncture: a nail or screw letting air out over hours or days
- Cold weather: pressure falls as temperature drops, so a cold snap can trigger the light overnight with no leak at all
- Natural seepage: all tyres lose a little air over months, and one can simply reach the threshold first
The response is the same in every case: check all four with a gauge and bring them back to the correct cold figure. If one is noticeably lower than the rest and drops again soon after, that points to a slow puncture rather than weather.
Flashing light: a system fault
A light that flashes for about a minute when the engine starts and then settles to a steady glow is a different message. That pattern points to a fault in the system itself rather than a soft tyre, most often a sensor with a flat battery or a sensor that has failed. It can also appear after a tyre change or wheel swap if the system has not been told about the new arrangement.
A fault like this will not clear by inflating the tyres, and because a broken TPMS is an MOT failure on cars first used from 2012, it is worth diagnosing rather than ignoring.
After topping up
Once the pressures are corrected, the light does not always go out instantly. Some cars clear it after a short drive on their own; others need a reset or relearn before the warning disappears. A light that stays on despite correct, confirmed pressures usually means either a reset is needed or a sensor has failed.
From the workshop: nine times out of ten in autumn, the light is just the first cold morning of the year, and every tyre is two or three PSI down. The tenth time it's a slow puncture. The gauge tells you which in about a minute, so never guess, a soft tyre you "topped up by eye" can still be the one with a screw in it.
Sources and accuracy. The symbol, the steady-versus-flashing behaviour and the MOT point here reflect common manufacturer practice and DVSA rules at the time of writing, which vary by model and can change. The car's own handbook is definitive. If anything here looks wrong, get in touch and we will check it and put it right.
Common questions
What does the TPMS warning light look like?+
It is usually an amber symbol shaped like a cross-section of a tyre, a horseshoe or bracket shape, with an exclamation mark in the middle. Some cars spell it out or show a small car with tyre pressures instead.
Why is my TPMS light on but my tyres look fine?+
A tyre can be several PSI low without looking flat. Cold weather alone can drop pressure enough to trigger it, and a slow puncture bleeds away gradually. Check all four with a gauge against the recommended figure rather than going by eye.
What does a flashing TPMS light mean?+
A light that flashes for around a minute at start-up and then stays on usually means a system fault rather than a low tyre, most often a failed sensor or a sensor battery that has died, rather than pressure itself.
Can I drive with the TPMS light on?+
It is safe to drive carefully to somewhere you can check and inflate the tyres, but not to ignore it. A steady light can mean a tyre is losing air, which gets worse with miles. Check the pressures at the first safe opportunity.