Warning lights
Tire pressure warning light on: what to do
The tire pressure warning light (a horseshoe with an exclamation mark) warns that at least one tire has lost pressure. If it flashes for a while and then stays on, on many cars it means a fault in the monitoring system itself.
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Reviewed by Daniel Morales, founder of Reprorace SL, on
Is it serious? Can I keep driving?
Carefully, and only as far as the garage. Slow down and check the tires as soon as you can stop safely. If one is clearly low, do not drive on: change the wheel or call for assistance. If they all look fine, drive slowly to a gas station and measure the pressures.
A careful, general answer: only someone who inspects the car can say whether it is safe to drive. When in doubt, stop somewhere safe and call for assistance.
Most likely causes
- Puncture or slow leak: a nail, a valve or a damaged rim letting air out little by little.
- Drop in temperature: pressure falls in the cold and the system warns even with no leak.
- System not reset: after inflating or changing tires, many indirect systems need resetting from the car's menu.
- Valve sensor: on direct systems, the sensor battery runs out or the sensor was not registered after a wheel change.
Listed from more to less common in general; on your car they may be different. A fault-code reading and a check at the garage confirm which one it is.
To understand it better: How often should you run diagnostics on your car? Can I diagnose my car myself?
Car system: Steering and suspension
What you can check yourself
Look at all four tires for one that is lower, a nail or a cut in the sidewall.
Measure the pressures cold and set them to the values on the car's label (in the door frame or the fuel flap).
After inflating, reset the system if your car asks for it, as the handbook explains.
If a tire loses pressure again within days, have it checked.
Safe checks only: with the engine off and cold whenever you look under the hood, without taking anything apart and without touching hot or moving parts.
Related fault codes
This symptom is usually mechanical and does not always store a generic fault code. Even so, reading the faults of every control unit helps to rule out other problems and to reach the garage with data.
How the ECO-LITE helps diagnose it
Plugged into the OBD socket, the ECO-LITE reads the fault codes of the control units that answer, with the freeze-frame data captured when the fault happened, and shows live data on your phone or computer. With your permission, your garage can see them remotely before you bring the car in.
What to look at here: tire pressure system codes when the car stores them in a reachable control unit; the speed of each wheel, used by indirect systems.
Frequently asked questions
Can I keep driving with the light on?
Only until you check the pressures, and at moderate speed. With a low tire, braking distances grow and the tire can fail.
Why does it come on when it is cold?
Because pressure drops with temperature. Set the pressures cold and the warning goes away.
I inflated them all and it is still on. What now?
Reset the system as the handbook says and drive a few miles. If it stays on, it may be a sensor or the system itself: have it checked.
Keep reading
- Steering and suspension: how they work and what fails
- Car pulls to one side: causes and what to do
- Car uses more fuel than normal: causes and what to check
- ABS or ESP warning light on: what it means and what to do
- Car symptoms: what they mean and what to do
- Check engine light on: what to do
- How to read and clear your car's fault codes
- OBD fault codes: what each one means