Tire pressure light on: solid vs flashing, and what to do
A solid tire pressure light means at least one tire is significantly low; a light that flashes first and then stays on means the monitoring system has a fault. Here is how to check safely and who fixes what.
Updated October 2026 · How we write guides
A solid light means at least one tire is significantly low, which hurts grip and braking. If a tire looks flat, is losing air fast or has sidewall damage, don't drive on it.
A solid tire pressure light means at least one tire is significantly underinflated, often from a cold snap or a slow leak. If it flashes for about a minute and then stays on, the TPMS system has a fault. Check all tires with a gauge, fill to the door-sticker pressure, and have a leaking tire properly repaired.
a tire looks flat or nearly flat, you can hear air escaping, the car pulls hard or shakes, or you see a bulge or cut in the sidewall. Pull over somewhere safe, away from traffic, and fit the spare if you can do it safely, or call roadside assistance. Call 911 if you are stuck in traffic danger.
Is it safe to drive with the tire pressure light on?
Only carefully, and only as far as the nearest air pump or a safe place to check. NHTSA says the TPMS symbol means at least one tire is significantly underinflated. An underinflated tire grips, steers and brakes worse, and it can overheat and fail. The light is not a “whenever you get to it” warning.
If the tires look normal, the car drives straight and the light came on during a cold snap, low pressure from the weather is the likely cause, and topping up usually solves it. If one tire keeps going low, you probably have a slow leak that needs a proper repair.
Solid or flashing: what the light is telling you
The TPMS light looks like a horseshoe (a U shape) with an exclamation mark inside, as AAA describes it. How it behaves matters:
- Solid from the start. One or more tires is low. Federal rules (FMVSS No. 138) require the light to come on within 20 minutes of a tire falling to 25 percent below the manufacturer’s recommended cold pressure, or a set minimum, whichever is higher. For example, if your door sticker says 35 psi, the light should be on by the time a tire drops to about 26 psi.
- Flashes for about a minute, then stays on. That is the system reporting a fault, not a low tire. NHTSA says a malfunction may be shown by the symbol flashing for 60 to 90 seconds and then staying lit. Common reasons include a failed sensor, a sensor with a dead internal battery, or new wheels or tires fitted without working sensors. The tires still need checking with a gauge, because a system fault means it can’t warn you.
NHTSA says TPMS has been required on passenger cars, light trucks and vans since model year 2008, and that it is not a substitute for checking your tires monthly with an accurate gauge.
What you can safely check yourself
- Find the right number. AAA says the recommended pressure is on the sticker in the driver’s door jamb (on some cars, the glove box or fuel door) and in the owner’s manual. Don’t use the number molded into the sidewall; that is the tire’s maximum, not your car’s setting.
- Check cold if you can. AAA says tires read 2-6 psi higher when hot, and suggests checking before driving or about three hours after. If you must check warm, don’t let air out to match the sticker.
- Check all four, and the spare if it has a sensor. One tire much lower than the others points to a leak, AAA notes.
- Look at each tire. Nails or screws in the tread, cuts, bulges or cracks in the sidewall are all reasons to stop and get help.
- Fill to the sticker pressure and drive a few miles. On many cars the light goes off once the pressures are right; some need a reset procedure in the owner’s manual.
- Recheck in a day. If the same tire is low again, it is leaking.
Cold weather is the classic trigger. AAA says pressure can drop 1-2 psi for every 10-degree drop in temperature, so a 30-degree overnight drop could take several psi out of every tire. Keeping tires at the right pressure also helps fuel economy; fueleconomy.gov estimates about 0.6 percent on average, up to 3 percent in some cases.
Symptom, common causes, and what a mechanic would check
| What you notice | Common causes | What a mechanic or tire tech would check |
|---|---|---|
| Solid light on the first cold morning | Temperature drop, tires slightly low already | All pressures, filled to the door sticker |
| Solid light, one tire much lower | Nail or screw, leaking valve stem, leak at the rim | Leak search; proper repair or replacement at a tire service |
| Flashes about a minute, then stays on | TPMS sensor fault or dead sensor battery, sensor missing | Sensor scan with a TPMS tool |
| Light on after new tires, wheels or a rotation | Sensor not installed, damaged, or not relearned | Sensor check and relearn procedure |
| Light on but all tires correct by gauge | Sensor fault, relearn needed, spare tire low | Sensor scan, spare pressure |
| Light plus pulling, shaking or noise | Very low or damaged tire | Tire condition; replace if damaged |
These are patterns, not a diagnosis. A technician who can see the tire will know more than any guide.
Mobile mechanic, mobile tire service, or tire shop?
A general mobile mechanic can usually check and set pressures, fit your spare, scan TPMS sensors and run a relearn on many cars. Fixing a puncture or replacing a sensor is different, because the tire has to come off the wheel. AAA says a proper repair is only for a clean puncture in the main tread no larger than 1/4 inch, never the sidewall or shoulder, and uses a combination plug and patch applied from inside after dismounting the tire. That needs a tire changer, which most mechanics’ vans don’t carry.
For those jobs, look for a mobile tire service (a separate trade with tire equipment in the truck) or a tire shop. NHTSA says tires should be replaced when tread is worn to 2/32 of an inch. More on who does what in what a mobile mechanic can do.
What it usually costs
Our standard price table has no single line for TPMS or puncture work, so the technician quotes after looking. Prices vary by vehicle and city.
| Item | Typical mobile price |
|---|---|
| Diagnostic | $85–130 (usually credited toward the repair) |
| Trip or service-call fee | $25–85 (often waived or credited if the repair is done the same visit) |
Filling tires yourself at a gas station air pump costs little or nothing, so start there. See mobile mechanic cost for other jobs.
What to do next
Check and fill all four tires to the door-sticker pressure, then watch the light. If it stays on, flashes at start-up, or one tire keeps going low, find a mobile mechanic in your city, book a mobile tire service, or send a request saying whether the light is solid or flashing and which tire is low. If the car also pulls or shakes, read car pulls to one side or steering wheel shaking.
A mechanic who can see the car will know more than any guide.
Questions people ask
Is it safe to drive with the tire pressure light on?
Only carefully and only to the nearest air pump or safe spot. NHTSA says the light means at least one tire is significantly underinflated, and low tires handle and brake worse. Don't drive on a tire that looks flat or damaged.
Why is my tire pressure light on when it's cold?
Cold air lowers pressure. AAA says pressure can drop 1-2 psi for every 10-degree drop in temperature, which can push a slightly low tire past the warning point overnight.
What does a flashing tire pressure light mean?
NHTSA says a TPMS light that flashes for 60 to 90 seconds and then stays on indicates a system malfunction, such as a failed sensor. Check your tires with a gauge, since the system may not warn you.
What pressure should my tires be?
Use the number on the sticker in the driver's door jamb or in the owner's manual, measured cold. AAA says not to use the pressure molded into the sidewall, which is the tire's maximum.
Can a mobile mechanic fix a slow leak?
A proper repair needs the tire taken off the wheel and patched from inside, so it usually goes to a mobile tire service or tire shop. A mobile mechanic can check pressures, fit the spare and scan TPMS sensors.
Where these facts come from
Every price and rule on this page comes from the sources below, checked September 2026. Prices vary by vehicle and city.
- NHTSA – Tire Safety Ratings and Awareness, TireWise (accessed Sep 2026)
- eCFR – 49 CFR 571.138, FMVSS No. 138 Tire pressure monitoring systems (accessed Sep 2026)
- AAA – How To Check Tire Pressure: Everything You Need To Know (accessed Sep 2026)
- AAA – What Is the Ideal Car Tire Pressure and How to Maintain It? (accessed Sep 2026)
- AAA – Tire Plug vs. Patch: Get the Right Tire Repair (accessed Sep 2026)
- AAA – 13 Common Car Problems Explained (accessed Sep 2026)
- U.S. DOE / EPA fueleconomy.gov – Keeping Your Vehicle in Shape (accessed Sep 2026)
- RepairPal – Repair cost estimator, national averages (updated Sep 3, 2026)
- MobileMechanics.ai – Prices that 90 listed mechanics publish on their own websites (checked Oct 2026)
Repairs a mechanic may quote for this
Common jobs behind this problem. A mechanic confirms which one, if any, after looking at the car.
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