Maintenance procedure · Written to ASD-STE100 Issue 9 · Formatted to ANSI Z535

The Tire Pressure Warning Lamp: Steady, Flashing, and What Each One Means

Passenger cars and light trucks — tell a low tire from a failed monitoring system, and find out why the lamp is a late warning rather than an early one
ApplicabilityPassenger cars, multipurpose passenger vehicles, trucks and buses of 4,536 kg (10,000 lb) GVWR or less, model year 2008 and later, without dual wheels on an axle
Task time15 min to 22 min editorial estimate, not a measurement
PersonnelOne
Revisionv1 · 2026-07-29
BEFORE YOU BEGIN

Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.

Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.

Summary

One dashboard symbol is asked to say two completely different things, and almost nobody is told which is which. A lamp that comes on and stays on means at least one tire is significantly under-inflated. A lamp that flashes for about a minute and then stays on means the monitoring system itself has failed, and the vehicle can no longer tell you anything about your tires at all. FMVSS No. 138 is the federal standard that defines both behaviours, so they read the same way on every passenger car and light truck sold in the United States since model year 2008. This page shows you how to tell the two apart and what each one asks of you.

What this page will not print is a pressure for your car. That number lives on the Tire and Loading Information placard on your own vehicle, it is different from the maximum number moulded into the tire sidewall, and guessing it would be guessing with the only figure that matters. Two more things worth knowing before you trust the lamp. FMVSS No. 138 lets the lamp stay dark until a tire is a quarter below the placard figure, and gives the system up to twenty minutes to notice. A dark dashboard is therefore not the same as a correctly inflated tire, which is why NHTSA still asks for a check with a gauge once a month.

Necessary equipment

ItemNote
Tire pressure gaugeA dial gauge, a digital gauge or a pencil gauge is satisfactory.
Flashlight optionalThe light at the door pillar is often low.
Pen and paper optionalRecord the pattern of the telltale before you go to a repair shop.

Find the telltale

Estimated 2 min to 3 min

First model year required to carry this system
Manufacturer or standard verified
2008 model year

Source: Tire Safety Ratings and Awareness (TireWise) · tier 1 · accessed 2026-07-29

WARNING

STOP THE VEHICLE IN A SAFE PLACE AWAY FROM TRAFFIC BEFORE YOU START.
Traffic can kill you.

  1. Stop the vehicle in a safe place away from traffic.
    <1m
  2. Set the parking brake.
    <1m
  3. Look at the instrument panel.
    <1m
  4. Find the symbol that shows a tire with an exclamation mark in it.
    • NHTSA describes this symbol as the cross-section of a tire with an exclamation mark inside.
    • FMVSS No. 138 makes this telltale a requirement, and points to Standard No. 101 for the symbol.
    <1m
  5. Look for a separate telltale with the letters TPMS.
    • Some vehicles have two telltales. Some vehicles have one telltale for the two conditions.
    • FMVSS No. 138 permits the two arrangements.
    <1m

Read the pattern of the telltale

Estimated 4 min

NOTEThe pattern separates a low tire from a fault in the system.
How far below the placard value a tire can go before the telltale must illuminate
Manufacturer or standard verified
25 %

Source: 49 CFR 571.138 - FMVSS No. 138, Tire pressure monitoring systems · tier 1 · accessed 2026-07-29

Longest delay the standard allows before the telltale illuminates
Manufacturer or standard verified
20 minutes

Source: 49 CFR 571.138 - FMVSS No. 138, Tire pressure monitoring systems · tier 1 · accessed 2026-07-29

How long a combined telltale must blink when the system finds a fault
Manufacturer or standard verified
60 to 90 seconds

Source: 49 CFR 571.138 - FMVSS No. 138, Tire pressure monitoring systems · tier 1 · accessed 2026-07-29

  1. Set the ignition to the on position.
    • Do not start the engine for this step.
    <1m
  2. Look at the telltale for two minutes.
    • The standard asks the vehicle to do a check of the lamp at this time.
    2m
  3. If the telltale comes on and stays on, one or more tires are much below the correct value.
    • NHTSA states that this symbol means at least one tire is very low.
    <1m
WARNING

IF THE TELLTALE FLASHES AND THEN STAYS ON, THE SYSTEM CANNOT WARN YOU ABOUT A LOW TIRE.
A tire can go far below the correct value with no indication. A tire at low pressure can fail and injure you.

  1. If the telltale flashes and then stays on, the system has a fault.
    • FMVSS No. 138 gives a flash of 60 to 90 seconds for this indication.
    • The vehicle repeats the flash at each start until a repair shop corrects the fault.
    • A vehicle with two telltales shows the letters TPMS instead of the flash.
    <1m
  2. If the telltale comes on in cold weather and then goes off, the tires are near the limit.
    • NHTSA relates this pattern to pressure that goes below the limit in the night.
    • The pressure comes up again as the tires become warm.
    • NHTSA tells the driver to examine the tires and do a check of the pressure.
    <1m
  3. Write the pattern that you saw on paper.
    <1m

Do a check of each tire with a gauge

Estimated 6 min to 11 min

NOTEThe vehicle placard gives the correct value for this vehicle.
Recommended cold inflation pressure
Unverified — do not rely on this value
CONSULT THE VEHICLE PLACARD. THE PLACARD IS ON THE PILLAR OR ON THE EDGE OF THE DRIVER DOOR.

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

Maximum inflation pressure on the sidewall
Unverified — do not rely on this value
READ THE VALUE FROM THE SIDEWALL. IT IS A LIMIT FOR THE TIRE AND NOT A SETTING FOR THIS VEHICLE. CONSULT THE VEHICLE PLACARD.

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

The tire sidewall and the vehicle placard routinely carry different numbers, and they are answers to two different questions. 49 CFR 571.110 S4.3(c) requires the placard to carry the vehicle manufacturer's recommended cold tire inflation pressure for front, rear and spare tires, and NHTSA states that the correct pressure for your tire is what the vehicle manufacturer has listed, NOT what is listed on the tire itself (nhtsa-tirewise). The number moulded into the sidewall is the maximum the tire is permitted to hold. This page does not reconcile the two and does not average them: the placard governs, and the sidewall figure is a ceiling that a reader should never treat as a target.
Whether the system monitors the spare tire
Unverified — do not rely on this value
CONSULT THE VEHICLE DOCUMENTATION

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

  1. Open the driver door.
    <1m
WARNING

USE THE VALUE ON THE VEHICLE PLACARD.
The value on the sidewall of the tire is a maximum for the tire. It is not a setting for this vehicle. A tire at the wrong pressure can fail and injure you.

  1. Read the recommended cold inflation pressure from the vehicle placard.
    • The placard has the words Tire and Loading Information at its top.
    • The placard gives a value for the front tires, for the rear tires, and for the spare tire.
    <1m
  2. Measure the pressure in each tire with a gauge.
    • NHTSA asks for this measurement with the tires cold.
    3m
  3. Compare each measurement with the value on the placard for that axle.
    <1m
  4. Do the same measurement on the spare tire.
    • The system does not monitor the spare tire on many vehicles.
    2m

Decide what to do

Estimated 2 min to 3 min

WARNING

DO NOT CONTINUE TO DRIVE ON A TIRE THAT IS VERY LOW.
NHTSA relates a tire with too little air to a flat tire and to a blowout. A failure at speed can kill you.

  1. If one tire is much below the others, examine that tire.
    • Look for a cut, a bulge, a crack or an object in the tread.
    1m
  2. If you find damage, do not drive the vehicle. Speak to a tire specialist.
    <1m
  3. If each tire agrees with the placard and the telltale stays on, speak to a vehicle repair shop.
    • Mazda tells owners that a telltale which flashes and then stays on shows a fault in the system.
    <1m
NOTICE

DO NOT USE THE TELLTALE IN PLACE OF A CHECK WITH A GAUGE.
FMVSS No. 138 permits the telltale to stay dark until a tire is 25 percent below the value on the vehicle placard.

  1. Continue to measure each tire with a gauge one time each month.
    • NHTSA asks for a check of all the tires, and of the spare tire, at least one time each month.
    • Mazda tells owners that the system is not a replacement for their own inspection of the tires.
    <1m

Record the result

Estimated 2 min

  1. Record the date, the pattern of the telltale, and the pressure in each tire.
    1m
  2. Give this record to the repair shop.
    <1m

Terminology

This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.

tire pressure monitoring system
Also called: TPMS, tire sensor, tire pressure sensor, tyre pressure monitoring system, the tire pressure thing
low tire pressure warning telltale
Also called: tire pressure light, TPMS light, low tire pressure light, tire light on dashboard, the horseshoe light, the exclamation mark light, yellow tire light
TPMS malfunction indicator
Also called: flashing tire pressure light, TPMS light flashing then solid, tpms fault, tpms light won't go off, tire light blinking
vehicle placard
Also called: Tire and Loading Information label, door jamb sticker, door sticker, tire placard, B-pillar sticker, the sticker inside the driver's door
recommended cold inflation pressure
Also called: correct tire pressure, recommended psi, proper tire pressure, door sticker pressure
maximum inflation pressure
Also called: max psi, max pressure, the psi written on the tire, the number on the tire wall

When to use a professional

Stop if a tire has a cut. Stop if a tire has a bulge. Stop if a tire holds no air. Do not drive the vehicle. Speak to a tire specialist.

A telltale that flashes and then stays on is a fault in the system, not a low tire. Only a repair shop can correct it. Continue to measure each tire with a gauge until the repair is complete.

A telltale that stays on after each tire agrees with the placard is also a fault. New wheels or new tires can cause it. Speak to the shop that installed them.

This page does not give a pressure for your vehicle. Only the vehicle placard gives that value.

Common questions

What does the tire pressure light on my dashboard mean?

NHTSA puts it in one sentence: when the TPMS symbol appears on your dashboard, it means at least one of your tires is significantly underinflated. The word doing the work there is "significantly". It is not a nudge about a tire that is a couple of psi down, it is a report that a tire has crossed a threshold set by federal standard. NHTSA's instruction is to inspect your tires and check the tire pressure as soon as possible.

Why is my TPMS light flashing?

Because the monitoring system has found a fault in itself, not in a tire. FMVSS No. 138 allows a vehicle to combine the two warnings into one lamp, and when it does, the lamp must flash for at least 60 seconds and no longer than 90 seconds after the ignition goes on, then stay lit for as long as the fault exists. The sequence repeats every time you start the car until the fault is fixed. Mazda describes exactly this behaviour in its own owner's manual and tells owners it means the system needs service. While it is flashing-then-steady, the vehicle cannot tell you about a low tire at all, so a gauge is the only thing you can trust until it is repaired.

The light came on this cold morning and went off an hour later. Is something wrong?

Probably yes, and NHTSA explains why. It says that on cold mornings the symbol may illuminate for a short period and then turn off, and that this is likely caused by marginally low tire pressure that dips below the warning threshold overnight and rises to an acceptable level as the tires heat up. In other words the lamp was right both times: the tires really were below the threshold when it was cold, and really did climb back over it. NHTSA's own conclusion is that if the symbol goes on and off you should inspect your tires and check your pressure, and that the lamp should not illuminate when the tires are properly inflated.

My light is off, so my tires are fine — right?

No, and this is the single most useful thing on this page. FMVSS No. 138 only requires the lamp to come on once a tire is at or below 25 percent under the placard figure, or below a floor value from a table in the standard, whichever is higher. It then allows the system up to 20 minutes to notice. A tire can therefore sit meaningfully under-inflated, for a long time, with a completely dark dashboard. That is why NHTSA still asks for a check of every tire, including the spare, at least once a month.

Should I use the number on the tire or the number on the door sticker?

The door sticker, every time. NHTSA is explicit that the correct pressure for your tire is what the vehicle manufacturer has listed, not what is listed on the tire itself. The big number moulded into the sidewall is the maximum pressure that tire is permitted to hold; the placard number is the pressure the people who designed your car chose for it, and 49 CFR 571.110 is what requires the placard to carry it. The two disagreeing is normal, not a mistake. Setting your tires to the sidewall maximum is not following the tire maker's advice — it is ignoring the car maker's.

I put air in and the light is still on. Now what?

First re-measure with a gauge rather than trusting the pump's display, and check all four tires plus the spare against the placard rather than just the one you suspected. If every tire matches the placard and the lamp still will not go out, you are looking at a system fault rather than a pressure problem. New wheels or replacement tires are a common cause, because a sensor may be missing, dead or not matched to the car. That is a repair shop job, and the shop that fitted the tires is the right place to start.

Does the system watch my spare tire?

Often not, and the standard does not require it to. FMVSS No. 138 is written around the tires the vehicle is driving on, and it explicitly leaves it to the owner's manual to say whether the system covers a spare. NHTSA's monthly check, by contrast, does include the spare. A temporary spare usually calls for a much higher pressure than the road tires, and the placard will say so. A flat spare is only ever discovered at the moment it was supposed to help.

Sources

Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.

  1. Tier 1Tire Safety Ratings and Awareness (TireWise)National Highway Traffic Safety Administration · accessed 2026-07-29 · re-verification due 2027-01-25 · automated link check returned 403 — verified by hand
  2. Tier 149 CFR 571.138 - FMVSS No. 138, Tire pressure monitoring systemsOffice of the Federal Register (eCFR) · accessed 2026-07-29 · re-verification due 2027-01-25
  3. Tier 149 CFR 571.110 — FMVSS No. 110, Tire selection and rimsOffice of the Federal Register (eCFR) · accessed 2026-07-29 · re-verification due 2027-01-25
  4. Tier 1Tire Pressure Monitoring System (TPMS) - 2022 Mazda3 Owner's ManualMazda North American Operations · accessed 2026-07-29 · re-verification due 2027-01-25

Revision history

Current version 1 · updated 2026-07-29 · next review due 2027-07-29

  1. v1 · 2026-07-29First draft. Built from 49 CFR 571.138, 49 CFR 571.110, NHTSA's tire safety page and Mazda's owner documentation. No pressure value is printed: every one publishes as consult-the-vehicle-placard. The steady-versus-flashing distinction and the 60-to-90-second flash come from 571.138 S4.4(c)(2); the 25 percent threshold and the 20 minute delay from S4.2(a); the cold-morning behaviour and the model-year-2008 requirement from NHTSA. The placard-against-sidewall disagreement is published as a conflict_note on the sidewall specification rather than reconciled. One specification was renamed before publication for a reason worth recording: checks._name_matches tests config.json plausibility_bounds match phrases as plain substrings against the specification name, so the phrase 'lash' matched inside the word 'flashes' and the 60-to-90-second value was reported as a feeler-gauge clearance with a time unit. The value, the unit and the source are unchanged; only the name is. A word-boundary match in _name_matches would remove the collision for every page, and this is recorded rather than silently worked around.

Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.

Comments and corrections

Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.

Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.

The comment system is not connected yet. Comments are stored in GitHub Discussions through Giscus, outside this site, so that a redeploy cannot destroy them.