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Why is my tire pressure light on?

Get it checked soonUpdated 3 sources2 min read

Short answer

A solid tire pressure (TPMS) light means one or more tires is significantly underinflated, often about 25% below the recommended pressure. Check all four tires with a gauge and fill them to the pressure on the sticker in the driver's door jamb; if the light flashes for a minute or so before staying on, the monitoring system itself has a fault and needs to be checked.

Safety first. If the light comes on while you're driving, hold the wheel firmly, ease off the gas and pull over somewhere safe before checking. A tire that's going flat fast, or one with visible damage, should be changed to the spare or towed, not driven on.

On this page

Step by step

  1. 1

    Pull over somewhere safe

    If the light came on at speed, grip the wheel with both hands, ease off the gas and get out of traffic. Look at all four tires for one that's visibly low or damaged.

  2. 2

    Find the right pressure

    Use the tire placard on the driver's door jamb or the owner's manual. Don't inflate to the maximum number printed on the tire's sidewall; that's the tire's limit, not your car's recommended pressure.

  3. 3

    Measure every tire with a gauge

    Check all four. Readings are most accurate when the tires are cold, meaning the car has sat for a few hours or been driven only a short distance.

  4. 4

    Inflate to the placard pressure

    Add air at a gas station or with a portable inflator until each tire matches the placard. Let out air if any tire is over.

  5. 5

    Drive a few minutes and watch the light

    The light usually goes off on its own after the pressures are corrected and you've driven a short distance. If it stays on, or if one tire keeps losing air, have the tire and the TPMS checked.

Solid light vs. flashing light

The tire pressure monitoring system (TPMS) has two different warnings, and they mean different things:

  • Solid from the start: low pressure. At least one tire is well under its recommended pressure. Check and fill.
  • Flashes for a minute or so, then stays on: a system fault. The monitoring system can’t do its job, so it can’t be trusted to warn you about a low tire. Air won’t clear it; the system needs to be diagnosed.

Why the light is set to come on “late”

The warning is designed for a significant drop, commonly around 25% under the recommended pressure. That means by the time it lights up, the tire is already quite low. It’s a backstop, not a substitute for checking your tires with a gauge.

Direct vs. indirect systems

Most cars use direct TPMS: a battery-powered sensor inside each wheel, usually part of the valve stem, reports the actual pressure. Some cars use indirect TPMS, which watches the anti-lock brake wheel-speed sensors and infers a low tire because it’s slightly smaller and spins faster. Indirect systems usually need a manual reset after you adjust pressures or rotate tires; your owner’s manual shows how.

When to see a pro

Have a tire shop look at it if:

  • One tire keeps losing air (a nail, a bad valve or a leaking bead).
  • The light flashes at startup, which points to a failed sensor or system fault.
  • You see a bulge, cut or cord showing on the sidewall. That tire needs replacing, not air.

Common follow-up questions

Why does my tire pressure light come on when it's cold outside?

Air pressure drops as temperature drops, roughly 1 psi for every 10°F, so tires that were borderline can trigger the light on a cold morning. Fill them back up to the placard pressure; they are still underinflated even if the light later goes off as the tires warm up.

What does a flashing tire pressure light mean?

A light that flashes for about a minute or more after you start the car and then stays on means the tire pressure monitoring system has a malfunction, such as a dead sensor battery or a failed sensor. Adding air won't fix it. Check your pressures manually until the system is repaired, because it may not warn you about a low tire.

Can I drive with the tire pressure light on?

Only far enough to check and fill the tires. Driving on a badly underinflated tire hurts braking and handling, wears the tire and can lead to a blowout. If a tire won't hold air, use the spare or get it repaired before driving on.

Why is the light still on after I filled my tires?

Give it a few minutes of driving first. If it stays on, a tire may still be low, a tire may be leaking, the system may need a reset (see your owner's manual), or a sensor may have failed.

Do all cars have a tire pressure monitoring system?

Every passenger vehicle sold in the U.S. since September 2007 has to have one, under the TREAD Act. Older cars may not, so check pressures yourself regularly with a gauge.

Sources

  1. 1.Schrader TPMS — What To Do When Your TPMS Light Turns On
  2. 2.Continental Tire — TPMS Warning Light: What It Means and What to Do
  3. 3.RepairPal — Tire Pressure Warning Light: What It Means, and What to Do About It

General information only, not a diagnosis. Your owner’s manual comes first. How we write these

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