Your tire pressure monitor light means at least one tire is underinflated or overinflated, or the sensor itself has failed

The tire pressure monitor light — usually a yellow or amber icon shaped like a tire with an exclamation mark — turns on when your vehicle's tire pressure monitoring system (TPMS) detects a problem. Most commonly, one or more tires have dropped below the recommended pressure, often by 10 percent or more. Less often, a tire is overinflated, or a sensor battery has died and stopped reporting. The light can also mean a sensor has malfunctioned or become loose.

The light does not mean you have a flat tire. It means the pressure inside one or more tires has drifted outside the safe range for your vehicle. Driving on underinflated tires reduces fuel economy, causes uneven wear, and can overheat the tire. Overinflated tires reduce traction and wear faster in the center. Either way, you should check and adjust your tire pressure within a day or two.

Key Takeaways

  • Check all four tire pressures with a manual gauge or at a gas station air pump — the light tells you a problem exists but not which tire or how much pressure is wrong.
  • Find your vehicle's correct tire pressure on a sticker inside the driver's door jamb, not on the tire sidewall, which shows the maximum pressure the tire can hold.
  • Adjust pressure when tires are cold (before driving or at least three hours after driving), because pressure rises as tires warm up and gives a false reading.
  • If all four tires are at the correct pressure and the light stays on, a sensor battery has likely died or a sensor has failed, and you will need a replacement.
  • A single tire losing pressure repeatedly points to a slow leak — a puncture, valve stem problem, or bead leak — that may need professional repair.

How to check your tire pressure correctly

You need a tire pressure gauge, which costs $5 to $15 and is available at any auto parts store or gas station. A digital gauge is easier to read than an analog dial gauge, but both work. You also need to know your vehicle's correct tire pressure, which is printed on a white or silver sticker inside the driver's door jamb — not on the tire itself. The number on the tire sidewall is the maximum pressure that tire can safely hold, which is usually higher than what your vehicle needs.

Check all four tires when they are cold, meaning before you have driven the vehicle or at least three hours after you stop driving. Tire pressure rises as the tire heats up from friction, so a warm tire will read 3 to 5 pounds per square inch (psi) higher than it actually is when cold. Remove the valve cap from the first tire, press the gauge onto the valve stem firmly until you hear air stop hissing, and read the pressure. Write it down. Repeat for all four tires, then replace all four valve caps.

If any tire reads more than 3 psi below the recommended pressure, or more than 3 psi above it, adjust it. Use the air pump at a gas station or a portable compressor at home. To add air, attach the pump nozzle to the valve stem and add air in short bursts, checking pressure every few seconds so you do not overfill. To release air, press the small metal pin inside the valve stem with a small tool or the back of your gauge. Check the pressure again after adjustment.

Why the light came on in cold weather

Tire pressure drops in cold weather because air contracts as temperature falls. For every 10 degrees Fahrenheit the temperature drops, tire pressure falls by about 1 psi. If you drove on warm days and parked overnight when temperatures fell, or if a cold front moved through, your tires may have lost enough pressure to trigger the light even though nothing is wrong with the tires themselves.

Check and adjust your tire pressure as described above. Once you do, the light should turn off within a few minutes of driving. If the temperature warms up again, your tire pressure will rise back toward normal. This is normal and not a sign of a problem — you do not need to let air out when it warms up. The system is designed to alert you when pressure drops below safe levels, and cold weather is the most common reason the light comes on in winter.

What to do if the light stays on after you adjust pressure

If all four tires are at the correct pressure and the light remains on, one of your tire pressure sensors has failed. Each tire has a small wireless sensor inside the valve stem or mounted on the wheel. These sensors have batteries that last 5 to 10 years. When a battery dies, the sensor stops reporting pressure to your vehicle's computer, and the light stays on.

You will need to replace the failed sensor. A tire shop or dealership can identify which sensor is not reporting and replace it for $50 to $250 per sensor, depending on the vehicle and whether the shop replaces just the sensor or the entire valve stem assembly. Some shops charge less if you bring your own wheel to them. If multiple sensors fail at once (which is rare), it usually means they are all the same age and were installed together, so you may want to replace all four at once to avoid repeated trips.

Until you replace the sensor, the light will stay on, but your tires are still safe to drive on as long as you check the pressure manually every week or two. The TPMS is a convenience feature that alerts you to pressure changes; it is not required for safe driving. However, if you ignore a real pressure problem because you assume the light is just a bad sensor, you could damage a tire or reduce fuel economy.

Diagnosing a slow leak

If one tire keeps losing pressure and the light comes back on within a few days or weeks after you refill it, you have a slow leak. The leak could be a puncture (often from a nail or screw), a faulty valve stem, or a bead leak where the tire does not seal properly against the wheel rim.

First, visually inspect the tire for nails, screws, or obvious damage. If you see a foreign object, do not remove it — mark it with tape and take the tire to a shop. If you see no obvious damage, take the tire to a tire shop and ask them to perform a pressure test. They will inflate the tire, submerge it in water or spray soapy water on it, and look for bubbles that indicate where air is escaping. A puncture in the tread can usually be patched for $15 to $30. A valve stem leak requires replacing the valve stem, which costs $20 to $50. A bead leak may require breaking the tire off the rim and reseating it, which costs $30 to $100.

Do not ignore a slow leak. A tire that loses pressure over time will eventually become dangerously underinflated, and a slow leak can become a blowout if the tire loses pressure suddenly while you are driving.

When the light flashes instead of staying steady

A flashing tire pressure monitor light means the TPMS system itself is malfunctioning, not that your tire pressure is low. This usually indicates a problem with the vehicle's receiver module or wiring, not with the sensors or tires. You should have this diagnosed by a dealership or shop with TPMS diagnostic equipment, because the problem cannot be fixed by adjusting tire pressure.

A flashing light is less common than a steady light, and it does not mean your tires are unsafe. However, you have lost the benefit of the pressure monitoring system, so you should check your tire pressure manually every month until the problem is fixed. The repair typically costs $100 to $300 depending on what component has failed.

Frequently Asked Questions

Can I drive with the tire pressure light on?

Yes, but only if you have confirmed that all four tires are at the correct pressure and the light is on because a sensor has failed. If a tire is actually underinflated, driving on it reduces fuel economy, causes uneven wear, and can overheat the tire. Check your pressure first before assuming the sensor is the problem.

Should I fill my tires to the pressure on the tire sidewall?

No. The number on the sidewall is the maximum pressure the tire can hold, not the pressure your vehicle needs. Always use the pressure listed on the sticker inside your driver's door jamb. Overinflating to the sidewall pressure will make your tires wear faster and reduce traction.

Why does my tire pressure light come on only in winter?

Cold air contracts, so tire pressure drops when outdoor temperature falls. For every 10 degrees Fahrenheit colder, tire pressure drops about 1 psi. Check and adjust your pressure in cold weather, and the light should turn off. This is normal and does not mean your tires are damaged.

How much does it cost to replace a tire pressure sensor?

A single sensor replacement typically costs $50 to $250 depending on your vehicle and whether the shop replaces just the sensor or the entire valve stem assembly. Some shops charge less if you supply your own wheel. Call ahead to ask for a quote.

Can I ignore the tire pressure light if I check my tires manually?

You can drive safely if you check pressure manually every week or two, but ignoring the light means you might miss a real pressure problem if you forget to check. The system is designed to alert you automatically, so a working TPMS is more reliable than remembering to check manually.