🛞 TPMS Warning Light: What It Means and What to Do

The tyre pressure monitoring system (TPMS) light — usually a cross-section of a tyre with an exclamation mark — comes on when one or more tyres drops below the recommended pressure. It's not always a puncture. Cold weather alone can trigger it.

Why pressure drops without a puncture

Tyre pressure naturally drops in cold weather — roughly 1 PSI for every 10°F (5°C) drop in temperature. If you've had a cold night and the light is on in the morning, checking and topping up the pressures is usually all that's needed.

Tyres also lose a small amount of pressure over time — about 1–2 PSI per month — so a tyre that was slightly low already can tip into warning territory.

How to check your tyre pressures

Your correct tyre pressures are usually printed on a sticker inside the driver's door jamb, or in the owner's manual. They're given in PSI (pounds per square inch) or BAR — petrol station air machines display both. Note that front and rear pressures are sometimes different, and the recommended pressure may increase if the car is loaded.

1. Check pressures when the tyres are cold — not after a long drive. A 10-minute drive to a petrol station is fine; a motorway run isn't.
2. Remove the valve cap from each tyre.
3. Press the gauge or air machine nozzle firmly onto the valve. If you hear air escaping, you haven't got a seal — press harder or adjust the angle.
4. Top up to the correct pressure. It's easy to overfill — add air slowly and recheck.
5. Replace all valve caps.

When it is a puncture

If one tyre is significantly lower than the others (more than 5–8 PSI), or if the car pulls to one side, you likely have a slow puncture or puncture. Inspect the tyre surface for nails, screws, or obvious damage. A slow puncture can often be driven carefully to a tyre shop; if the tyre is very low or visibly deflated, don't drive on it — fit the spare or call recovery.