The TPMS warning light: what it means and what to do
5 min readBy Wheel Fit
The short answer: a steady TPMS light means at least one tyre is genuinely low — stop somewhere safe and check all four. A light that flashes for a minute then stays on usually means a system or sensor fault, not a flat tyre.
What TPMS is
Tyre Pressure Monitoring System. It has been mandatory on new cars in the UK and EU since 2014, and it comes in two flavours:
- Direct. A battery-powered sensor inside each wheel measures actual pressure. Accurate, and can usually tell you which corner. The batteries last several years and are not replaceable — the sensor is.
- Indirect. No sensors. It infers pressure from wheel speed via the ABS: a deflating tyre has a smaller rolling radius so it turns fractionally faster. Cheaper, but it needs resetting after any pressure change and cannot detect all four going down evenly.
Reading the light
| Behaviour | Usually means |
|---|---|
| Comes on steady while driving | Genuine pressure loss. Check all four. |
| On at start-up in cold weather | Air contracting overnight. Still check and reinflate. |
| Flashes ~60 seconds, then stays on | System fault — dead sensor battery, or a sensor missing after a wheel change. |
| Comes and goes | A slow puncture, or a sensor on its way out. |
The first cold morning of autumn
Every year, the first proper cold snap sets off TPMS lights across the country. Air contracts as it cools, and pressure drops with it — roughly 1 to 2 PSI for every 10°C.
That is not a false alarm. The pressure really has dropped and the tyre really is under-inflated. Top it up to the figure on the door plate rather than ignoring it.
Never just reset it
It is tempting, especially with indirect systems where reset is a menu option. Do not. Resetting an indirect system tells the car "these pressures are correct" and it will calibrate against a genuinely flat tyre.
Check and correct the pressures first, then reset.
Sensors and tyre changes
If your car has direct TPMS, the sensors live inside the wheels. Any competent fitter works around them, but they are consumable: batteries typically last five to ten years, and a sensor damaged during a rushed tyre change is a real cost.
Tell us when you call whether your car has TPMS so we arrive prepared. Call 07989 606060, or read about checking pressures properly.
