Tire pressure light: what it means and what to do
A solid tire pressure light means at least one tire is far below its recommended pressure. Under the federal rule for these systems (FMVSS 138), the light must come on when a tire is 25% or more under the pressure the carmaker recommends. Check all four tires with a gauge at the next safe stop and fill them to the pressure on the sticker in the driver’s door jamb. If the light flashes for about a minute when you start the car and then stays on, the tire pressure monitoring system (TPMS) itself has a problem.
On this page (10 sections)
The short answer
| What you see | What it means | What to do |
|---|---|---|
| Light stays on | One or more tires are about 25% or more below the recommended pressure | Stop somewhere safe soon, look at the tires, check them with a gauge, and add air |
| Light flashes for about 60–90 seconds at start-up, then stays on | The TPMS has a fault and may not warn you about low pressure | Check the pressure with a gauge yourself, and have the system checked by a shop |
| On after a cold night, off after a few miles | A tire is close to the warning level; cold air lowered the pressure | Check the tires before driving and fill them to the door sticker pressure |
| On after new tires, new wheels, or a rotation | The system may need a reset, or a sensor didn’t work with the new parts | Follow the reset steps in your owner’s manual; if it stays on, go back to the tire shop |
Based on FMVSS 138 (49 CFR 571.138). Your owner’s manual has the details for your car.
What the tire pressure light means
The light is the warning lamp of the tire pressure monitoring system. Federal rule FMVSS 138 requires this system on cars, SUVs, pickups, and vans with a gross vehicle weight rating of 10,000 pounds or less (except those with dual rear wheels) built on or after September 1, 2007.
The rule says the light must come on within 20 minutes after a tire drops to whichever is higher:
- 25% below the carmaker’s recommended cold pressure, or
- a minimum pressure set in the rule for that type of tire.
Example: if the door sticker says 35 psi, 25% below that is about 26 psi. So by the time the light comes on, the tire is already well under the right pressure. The light means “significantly low,” not “a little low.”
The symbol is a horseshoe-shaped tire cross-section with an exclamation point inside. Some cars show which tire is low; others only show one light for all four.
Solid vs flashing tire pressure light
Solid: a tire is low. This is the common case.
Flashing, then solid: the system has a malfunction. FMVSS 138 lets carmakers use one light for both jobs: in that case, the light must flash for 60 to 90 seconds after you turn the car on, then stay lit, and repeat this on every start until the problem is fixed. Other cars use a separate light with the letters “TPMS.”
When the malfunction light is on, the system may not be able to warn you about low pressure. The owner’s manual statement that the rule requires names one common cause: replacement tires or wheels that keep the system from working. A shop with a TPMS tool can read which sensor isn’t reporting. Until then, check the tires with a gauge yourself.
What to do when the tire pressure light comes on
- Slow down and find a safe place to stop. The owner’s manual statement required by FMVSS 138 says to stop and check your tires as soon as possible.
- Look at each tire. If one is flat or clearly low, don’t keep driving on it. Driving on a badly underinflated tire makes it overheat and can lead to tire failure. Put on the spare or call for roadside help.
- Check all four tires with a gauge (and the spare, if your car monitors it). The number on the dash, if your car shows one, is a good guide; a gauge is better.
- Add air to the recommended pressure. Use the number on the sticker in the driver’s door jamb or in your owner’s manual, not the maximum pressure printed on the tire.
- Drive a few miles. On many cars the light turns off by itself once the pressure is right. If it doesn’t, use the reset steps in your manual (see below).
- Check again the next day. If one tire keeps losing air, it may have a nail or a leaking valve. Have it repaired.
Why the light comes on in cold weather
Air pressure drops as the temperature drops. Michelin says tires lose about 1 psi for every 10 °F drop in temperature, on average.
Example: tires set to 35 psi in a 70 °F garage lose about 5 psi on a 20 °F morning outside, down to about 30 psi. That alone usually won’t trigger the light. But if a tire was already a few psi low, the cold can push it past the warning level overnight. As the tires warm up on the road, the pressure rises and the light may go off. The tire is still low; check it.
The recommended pressure on the door sticker is a cold pressure. Check it before you drive, or after the car has been parked for a few hours. Michelin advises checking at least once a month, when the tires are cold.
How to reset the tire pressure light
There are two kinds of systems, and they reset differently:
- Turns off by itself. Many systems read the pressure from a sensor inside each wheel. Once all tires are at the right pressure, the light goes off after a short drive. FMVSS 138 lets the light stay on until the pressure is corrected or until it is reset the way the carmaker describes.
- Needs a reset or calibration. Some systems estimate the pressure from how fast each wheel turns, and they must learn the new “normal” after you add air. Honda, for example, says its TPMS needs to be calibrated after a tire is filled or replaced, or the tires are rotated. The steps are in a settings menu or on a button, depending on the model.
The exact steps differ by make, model, and year, so use your owner’s manual. Set all four tires to the right cold pressure first; a reset with a low tire teaches the system the wrong number. If the light comes back after a reset, a tire is still losing air or a sensor has failed. After a tire rotation or new tires, some cars also need the shop to relearn the sensor positions.
The light is not a monthly check
Because the light waits until a tire is about 25% low, it can’t replace a gauge. The owner’s manual statement required by FMVSS 138 says each tire, including the spare, should be checked monthly when cold. A tire a few psi low won’t turn on the light, but it still costs you:
- Gas mileage. Fueleconomy.gov says underinflated tires lower gas mileage by about 0.2% for every 1 psi drop in the average pressure of all four tires. See how to calculate MPG to spot a drop.
- Tire life and handling. The same manual statement says underinflation reduces tread life and may affect handling and stopping. Our guide on how long tires last covers tread checks.
Our car maintenance checklist puts the pressure check in the monthly list. For other lights on the dash, see dashboard warning lights.
What to write in your log
When the light sends you to a tire shop, write down:
- The date and odometer reading
- Which tire was low, and the pressure you found
- The cause, if the shop found one (nail, valve, sensor)
- What was done and the cost
A tire that loses air again and again shows up quickly in a log.
FAQ
Can I drive with the tire pressure light on?
Only as far as the nearest safe place to check the tires. The light means a tire is about 25% or more below its recommended pressure. If a tire looks flat, don’t drive on it: use the spare or call for help. Your owner’s manual says what your car allows.
Why is my tire pressure light on when my tires look fine?
A tire can be 25% low and still look normal. Check each tire with a gauge. Other common reasons: cold weather, a low spare that the system monitors, or a system that needs a reset after you added air.
Why is my tire pressure light flashing?
A light that flashes for about 60 to 90 seconds at start-up and then stays on means the TPMS has a fault, under FMVSS 138. The system may not warn you about low pressure until it is fixed, so check the tires with a gauge and have a shop look at the system.
How long does it take for the tire pressure light to go off?
On many cars it goes off after a short drive once all tires are at the right pressure. Some cars need a reset or calibration first. If it stays on, check the pressure again and follow the steps in your owner’s manual.
What PSI should my tires be?
Use the pressure on the sticker in the driver’s door jamb or in your owner’s manual. It is a cold pressure. The number on the tire’s sidewall is the maximum the tire can hold, not the right pressure for your car.
Sources
- 49 CFR 571.138, Federal Motor Vehicle Safety Standard No. 138, Tire pressure monitoring systems (application, 25% threshold, 20 minutes, malfunction light flashing 60–90 seconds, required owner’s manual statement, September 1, 2007) (checked November 12, 2026): govinfo.gov
- Michelin, How to prepare your car for winter (about 1 psi per 10 °F; check monthly when cold) (checked November 12, 2026): michelinman.com
- U.S. Department of Energy and EPA, Keeping your vehicle in shape (0.2% per 1 psi) (checked November 12, 2026): fueleconomy.gov
- Honda Info Center, How to calibrate the tire pressure monitoring system (TPMS), 2019 Civic Hatchback (checked November 12, 2026): hondainfocenter.com
- Consumer Reports, What the dashboard warning lights mean in your car (tire pressure light; updated April 23, 2026; checked November 12, 2026): consumerreports.org