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Close view of a car instrument cluster with the amber tire pressure warning symbol lit

Fix-it guides 路 Tires, Steering and Suspension

Tire pressure light on? What it means and what to do

By the Boca Auto Care Editorial Team 路 Reviewed October 28, 2026 路 How we write guides

Short answer

A steady tire pressure light means at least one tire is roughly 25 percent or more below the pressure on your door-jamb sticker. A light that flashes for about a minute at startup and then stays on means the monitoring system itself has a fault, most often a sensor with a dead battery. Check all four tires with a gauge before you do anything else.

Get it checked soonA steady light is a real low tire until a gauge proves otherwise, so check it the same day. If a tire looks flat or you hear flapping, pull over and use the spare or call for help; a flat is ruined within a mile or two. A flashing light is not an emergency, but until it is fixed the system cannot warn you about a real leak.

Every passenger car and light truck built for the US market since September 2007 has a tire pressure monitoring system, required by federal safety standard FMVSS 138. The warning must come on within 20 minutes once any tire drops to 25 percent below the recommended cold pressure. On a car with a 35 psi placard, that is about 26 psi, low enough to run hot, wear the shoulders and lengthen stopping distances.

The same standard gives the light a second job. If the system detects a fault, such as a sensor that stopped transmitting, the symbol flashes for 60 to 90 seconds at every startup and then stays solid. Telling these two patterns apart is the most useful thing you can do, because one points at air and the other points at electronics.

Most cars use direct TPMS: a battery-powered sensor inside each wheel, usually built into the valve stem. Some Honda, Mazda, Volkswagen and Audi models use indirect TPMS, which has no sensors and instead watches ABS wheel-speed signals for a tire that spins faster because it has shrunk. Indirect systems need a manual reset after you adjust pressure.

Symptoms

  • Amber horseshoe-shaped symbol with an exclamation point stays lit on the dash
  • The light comes on during a cool morning and goes out after a few miles of driving
  • The light flashes for 60 to 90 seconds after you start the car, then stays on
  • The dash shows one tire reading several psi lower than the other three
  • The light came on right after a tire rotation, new tires or a flat repair

Likely causes and what they cost

1. Tire genuinely low from a temperature drop or normal seepage

free to $2 at an air machine
common 路 DIY possible

Air pressure falls about 1 psi for every 10 degree Fahrenheit drop in temperature, and every tire loses roughly 1 psi a month through the rubber even with no leak. A tire that was set slightly low in summer can cross the warning threshold on the first cool morning. If the light goes out after 10 minutes of driving, the tire warmed up just enough to clear it, but it is still low.

The fix: Inflate all four tires, cold, to the pressure on the driver's door-jamb placard, not the maximum printed on the sidewall. Drive a few miles and the light should clear on its own.

2. Slow leak from a nail, screw or bead seal

$30-$60 for a puncture repair; $40-$80 to reseal a bead
common 路 Shop job

If one tire keeps dropping a few psi every few days while the others hold, something is letting air out. Screws and nails in the tread are the usual cause. Corroded aluminum wheels can also leak slowly where the tire bead seats against the rim, which shows up as bubbles around the edge of the wheel.

The fix: A tread puncture under 1/4 inch is repaired from inside with a plug-patch after the tire is removed from the wheel. A leaking bead is cleaned, the rim is wire-brushed and the tire is remounted with bead sealer.

3. Dead TPMS sensor battery

$90-$180 per wheel with a quality aftermarket sensor at a tire shop; $250-$330 per wheel with an original sensor at a dealer
common 路 Shop job

Each direct sensor has a sealed lithium battery that typically lasts about 5 to 10 years. When one dies, the system loses contact and the light starts the flash-then-solid pattern. Because all four sensors were installed at the same time, the others usually follow within a year or two.

The fix: The tire is broken down, the old sensor is replaced and the new one is programmed to the car with a relearn tool. Many owners replace all four at once when buying new tires, since the tires come off anyway.

4. Sensors not relearned after a rotation or tire swap

$50-$90, often free at the shop that did the rotation
less common 路 Shop job

Many cars need to know which sensor sits at which corner. After a rotation, new wheels or a replaced sensor, the car may show a fault or flag the wrong tire until the sensor IDs are relearned. Some models relearn on their own after 10 to 20 minutes of driving; others need a scan tool.

The fix: A relearn with a TPMS tool, or the procedure in the owner's manual, which on some cars involves a sequence of key turns and deflating each tire in order.

5. Corroded or leaking valve stem

$25-$50 per wheel for a service kit installed
less common 路 Shop job

Clamp-in TPMS sensors use an aluminum stem with a nickel-plated valve core. Moisture and salt cause the two metals to corrode together, the core starts to seep and the stem can crack when someone tightens an air chuck on it. A missing valve cap speeds this up.

The fix: A sensor service kit replaces the nut, grommet, core and cap. If the stem itself is cracked, the whole sensor is replaced.

6. Indirect system not reset after adding air

free
less common 路 DIY possible

On cars that use wheel-speed TPMS, the computer learns the current tire sizes as the baseline. If you add air without telling it, or install new tires, the warning can stay on or reappear. The tires may be perfectly fine.

The fix: Set every tire to the placard pressure, then run the calibration from the vehicle settings menu or press the TPMS set button, and drive normally while it relearns.

Costs are typical South Florida ranges for parts and labor, for budgeting only.

What you can check yourself

  1. 1
    Note how the light behaves at startup

    Start the car and watch the symbol for a full 90 seconds. Steady from the start points to low pressure. Flashing for about a minute and then steady points to a sensor or system fault.

  2. 2
    Read the correct pressure from the placard

    Open the driver's door and find the sticker on the door jamb. It lists the cold pressure for front and rear, which can differ. The MAX PRESS number on the tire sidewall is the tire's limit, not your target.

  3. 3
    Gauge all four tires cold

    Check before driving or after the car has sat for three hours out of direct sun. A $10 to $15 digital gauge is more reliable than most gas station hoses. Write the four numbers down. If one is 5 or more psi lower than the rest, suspect a leak.

  4. 4
    Look for the leak

    Roll the car forward half a turn so you can see the whole tread. Look for a screw head or nail. Mix dish soap and water in a spray bottle and mist the tread, the valve stem and the edge of the rim; growing bubbles mark the leak. Do not pull a nail out, it is plugging the hole until a shop can repair it.

  5. 5
    Reset if your manual calls for it

    On indirect systems, or cars with a TPMS set button, run the reset only after all tires are at the correct pressure. Resetting with a low tire teaches the system that low is normal.

When to take it to a shop

  • One tire loses air again within a few days of being filled
  • You found a nail, screw or bubbles in the tread or at the rim
  • The light flashes at startup and then stays on, which means a sensor or module fault
  • The light stays on after all four tires are confirmed correct with a gauge and the car has been driven 15 minutes
  • A tire has a bulge, a cut in the sidewall or was driven any distance while flat
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The Florida factor

South Florida's version of a cold snap catches a lot of drivers. When a winter front pushes through and the morning low falls from the mid 70s into the 40s or low 50s, tire pressure can drop 3 to 4 psi overnight. A car parked outside in Boca or Parkland lights up at 7 a.m. and goes quiet by lunch. That is the system working, and the fix is to top the tires up to the placard number on a cool morning rather than ignoring it until the next front.

The reverse happens in summer. After an hour on I-95 and a sit in a sun-baked Glades Road parking lot, a tire can read 4 to 6 psi above its cold number. Never let air out of a hot tire to match the sticker; it will be underinflated once it cools. Set pressure in the morning, or in a shaded garage.

Salt air is hard on TPMS hardware. Cars that live east of Federal Highway, near the Intracoastal or along A1A in Highland Beach and Deerfield, see more corroded aluminum valve stems, so keep the caps on and ask for a sensor service kit when tires are replaced. Snowbird cars that sit from April to November commonly come back to two or three tires below the warning line and, on older cars, a sensor that quietly died over the summer.

Notes for specific makes

  • Honda: Many recent Civic, Accord and CR-V models use indirect TPMS with no wheel sensors. After adjusting pressure or rotating tires, run TPMS Calibration from the vehicle settings menu, then drive normally so it can finish learning.
  • Toyota: Several Toyota trucks and SUVs monitor the full-size spare as well, and many models have a TPMS reset or SET button under the dash or in the glovebox that must be held after changing pressures or tire sizes.
  • Ford: Many Ford trucks and SUVs need a TPMS relearn after a rotation, which uses a scan tool or a key-cycle and deflation sequence in the owner's manual. Skipping it can show the wrong corner as low.

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Frequently asked questions

Is it safe to drive with the tire pressure light on?

Only as far as the nearest air pump, and only after a quick look confirms no tire is flat. A tire at 25 percent below spec runs hotter, grips less in rain and wears faster. If the light is the flashing type, the tires may be fine, but you have lost your early warning, so check pressures by hand weekly until it is repaired.

Why does the light turn off after I drive for a while?

Driving heats the tires and raises pressure a few psi, which can lift a marginal tire back above the threshold. The tire is still low when cold. Add air in the morning and the cycle stops.

Can I replace a TPMS sensor battery myself?

On almost all cars the battery is sealed inside the sensor, so the whole sensor is replaced. The job requires dismounting the tire and programming the sensor to the car, which needs shop equipment.

Related guides

Nail in your tire: plug, patch, or replace?
A puncture up to 1/4 inch in the main tread area can be permanently repaired with a combination plug-patch installed from inside the tire after it is removed from the wheel. A plug pushed in from outside is an emergency fix to get you to a shop. Anything in the shoulder or sidewall, larger than 1/4 inch, or on a tire driven while flat means a new tire.
Uneven tire wear: what each wear pattern is telling you
The shape of the wear tells you the cause. Both outer edges worn means the tires ran underinflated, a worn center means too much air, one edge worn means camber is off, a sawtooth feel across the tread means toe is off, and scalloped dips mean worn shocks or struts. Fix the cause before buying tires, or the new set will wear the same way.
How old is too old for tires, even with good tread?
Most tire makers say to retire a tire 10 years after it was made no matter how much tread is left, and to have it inspected every year once it passes 5 years. Several automakers have set a stricter 6-year limit. In South Florida heat and sun, plan on the earlier end of that window, especially for cars that sit and for spares.
Why does my car pull to one side when I drive?
The most common reasons a car pulls to one side are uneven tire pressure, an alignment knocked out by a pothole or curb, and a tire with an internal defect that steers the car. Check the pressures first because it is free, then have the alignment measured. A pull that gets stronger when you brake is a brake problem, not an alignment problem.
How do I prepare my car for a hurricane in Florida?
Keep at least half a tank of fuel (or 50-80% charge on an EV) all season, photograph the car and its documents, confirm you carry comprehensive coverage, and park on the highest ground you can reach away from trees. Do the mechanical checks, like tires, wipers and battery, before a cone appears on the map, because shops and parts stores fill up fast.

More on this job: Tires & Wheels in Boca Raton, costs and how to choose a shop

Sources

General information, not a diagnosis. A car problem can have causes a guide cannot see, so have anything safety-related inspected in person. Read our editorial policy.