Since the system became a legal requirement on new passenger cars in the European Union in 2014, the majority of cars on UK roads built since then carry some form of TPMS. It comes in two main types, and knowing which you have helps you understand the warning.
Two types of TPMS
- Direct TPMS uses a small sensor inside each wheel that measures actual pressure and sends it to the car. Sensors run on a built-in battery.
- Indirect TPMS uses the ABS wheel speed sensors to detect a tyre that is rotating faster than the others because it has less air. It does not measure pressure directly and usually needs resetting after you adjust pressures.
Solid light versus flashing light
A steady light normally means one or more tyres are below the set pressure. A light that flashes for about a minute when you start the car and then stays on usually points to a fault in the system, such as a failed sensor, a flat sensor battery or a missing sensor after a wheel change. Always check your handbook, as wording varies by manufacturer.
What to do when the light comes on
- Slow down and avoid heavy braking or hard cornering.
- Pull over safely and look at the tyres. Check for obvious flats or damage.
- Use a gauge to check all four tyres when cold, if possible, and inflate to the figures in your handbook or door frame label.
- Drive a short distance and see whether the light goes out. Indirect systems often need a manual reset through a menu or button.
- If the light stays on or returns, there may be a slow puncture, a faulty sensor or a leaking valve.
Cold weather can lower pressure enough to trigger the warning on a frosty morning. A temporary light that clears after a short drive is often this, but it still means pressures should be checked.
When the sensor itself is the problem
Direct sensors contain a battery that eventually runs flat. They can also be damaged during tyre changes, corroded by moisture, or knocked by a pothole. If the pressures are correct but the light persists, a technician can scan the sensor and replace it. The valve stem and seal are also replaced when a tyre is changed to prevent leaks.
Our TPMS and valve replacement service covers sensor checks, valve replacement and resetting the system on site. If the cause is a puncture, the tyre may need puncture repair or replacement through mobile tyre fitting.
Run-flat tyres and TPMS
On a car with run-flats, the warning is especially important because the tyre can look normal when deflated. See run-flat tyre puncture and slow puncture signs.
Do not ignore the warning
Driving on low tyres affects handling, braking distances and tyre life, and can lead to the kind of failure described in our motorway blowout guide. If you are not sure why the light is on, have the car checked.
We attend homes and workplaces across areas like Birmingham, Manchester, Croydon and Watford. Call now for a quote on 0800 772 0355, or book now.
Quick checklist
- Check all four tyre pressures cold.
- Reset the system if your car requires it.
- Look for nails, damage and valve leaks.
- Have sensors tested if the light stays on.
- Ask for sensors to be checked whenever new tyres are fitted.
Common mistakes with the pressure warning
Many owners assume the light is a fault and ignore it, or assume it is only about cold weather. Neither is safe. Another mistake is inflating to the pressure printed on the tyre sidewall: that figure is the tyre maximum, not the recommended pressure for your car. The correct number is in the handbook, on the fuel flap or on the door pillar label.
Also remember that the spare wheel on some cars has its own pressure, and that a heavily laden car usually needs a higher pressure setting, which is shown on the same label. If you adjust pressures for a load and then unload, reset them.
Sensors and new tyres
When new tyres are fitted, the sensor should be checked, and the valve seal and core replaced if the fitter recommends it. Corroded valve stems on older alloy wheels are a frequent cause of slow leaks and false warnings. If a tyre is changed and the light later appears, mention this to the fitter, as the sensor may have needed relearning to the car.
Frequently Asked Questions
Why is my tyre pressure light on when tyres look fine?
Tyres can be low without looking flat, and temperature changes alter pressure. Check each tyre with a gauge.
What does a flashing TPMS light mean?
Often a system fault such as a failed sensor. Check your handbook and have the system scanned.
Do I need to reset TPMS after inflating?
On many cars, particularly indirect systems, yes. The method is in the handbook.
Can sensors be replaced at my home?
Yes, in most cases. Call now for a quote on 0800 772 0355.
Related Help
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