Tire Pressure Light On? Here's What to Do

What Is TPMS and How Does It Work?

I'm Anthony Calhoun, and I've been turning wrenches for 25 years as an ASE Master Technician. I graduated from GM's ASEP program back in 2003, and since then I've replaced more TPMS sensors than I'd care to count. Let me give you the real scoop on that little tire pressure light.

TPMS has been required on every new passenger vehicle sold in the U.S. since 2007, per the TREAD Act that NHTSA enforced after the Firestone tire recall in the early 2000s. That recall involved tires failing on Ford Explorers at highway speeds, and it killed people. So Congress said every new car needs a system that warns you when your tire pressure is dangerously low.

There are two types of TPMS:

Direct TPMS (Most Common)

Each tire has a small sensor mounted inside, attached to the valve stem or banded to the wheel. The sensor measures actual air pressure and temperature, and it transmits that data wirelessly to your car's computer. These sensors have a battery inside them — and that battery lasts about 5-10 years before it dies. You can't replace the battery; you replace the whole sensor.

Indirect TPMS

Used by some manufacturers (BMW used this for a while, some Mazdas, some Hondas). This system doesn't use pressure sensors. Instead, it uses the ABS wheel speed sensors to detect when one tire is spinning faster than the others — which happens when a tire is low because its diameter is smaller. It's cheaper but less accurate, and you have to recalibrate it every time you adjust tire pressure or rotate tires.

Why Your Tire Pressure Light Is On

Here are the real reasons your TPMS light is staring at you right now:

1. You Actually Have a Low Tire (Most Likely)

Before you panic — the most common reason is the simplest one. You have a tire that's low on air. Could be a slow leak from a nail, a small puncture, a cracked valve stem, or a bead leak where the tire meets the rim (common on alloy wheels with corrosion). The system is doing exactly what it's supposed to do.

2. Temperature Drop

This is the number one call I get every October and November. For every 10 degrees Fahrenheit the temperature drops, your tires lose about 1 PSI. So if your tires were at 32 PSI in August and it's now 30 degrees colder in November, you could easily be at 29 PSI — enough to trigger the light on a car that wants 32 PSI. This doesn't mean something is wrong with your tires. It means you need to add air.

3. Dead TPMS Sensor Battery

Those little sensors have lithium batteries inside, and they last 5-10 years. When the battery dies, the sensor can't transmit, and the light comes on — usually as a flashing light first, then solid. If your car is 7+ years old and you've never replaced a TPMS sensor, this is a strong possibility.

4. Damaged Sensor

Sensors get damaged during tire mounting (bad technician), from hitting a big pothole, or from corrosion. Aluminum valve stem sensors are especially prone to corrosion from road salt — I see this constantly on cars in the northern states.

5. Sensor Not Relearned After Tire Rotation

When tires are rotated, the sensors move to different wheel positions. Most cars need a "relearn" procedure so the computer knows which sensor is at which corner. If the shop that rotated your tires didn't do the relearn (some skip it to save time), the light might come on or display incorrect positions.

Step-by-Step: What to Do When the Light Comes On

Step 1: Don't Panic — But Don't Ignore It

A TPMS light doesn't mean your tire is about to blow. It means pressure is low. But driving on a significantly underinflated tire can cause tire failure, so take it seriously within the next few hours.

Step 2: Check All Four Tires Visually

Walk around the car. Does any tire look obviously low or flat? If one is visibly sagging, that's your problem tire. If they all look okay, the difference might be small (a few PSI) and not visible to the eye.

Step 3: Check Pressure With a Gauge

Get a tire pressure gauge — a decent digital one costs $8-$15 at any auto parts store. Check all four tires (and the spare if your car has TPMS on the spare, which some do). Compare to the numbers on the driver's door jamb sticker.

Step 4: Add Air to Any Low Tires

Most gas stations have air machines. Some are free, some cost $1-$2. Fill each tire to the recommended PSI. If you're doing this on a cold morning, fill to the exact number. If you're doing it after driving (tires are warm), add 2-3 PSI above the recommendation, as tires gain pressure when warm.

Step 5: Drive for 10-15 Minutes

The TPMS light usually goes off on its own after driving for a bit once pressure is correct. The sensors transmit periodically (usually when the car is moving at 15+ mph), so give it a few miles.

Step 6: If the Light Comes Back

If the light turns off but comes back within a few days, you have a slow leak. Most slow leaks are from nails or screws in the tread (repairable for $15-$30 at any tire shop) or from corroded wheel bead surfaces (requires dismounting, cleaning, and resealing).

How to Reset the TPMS Light

The reset procedure varies by manufacturer. Here are the most common approaches:

Many Vehicles (Toyota, Lexus, Honda, others): Reset Button

There's a TPMS reset button, usually under the steering column or in the glove box. With the key in the ON position (engine off), hold the button until the TPMS light blinks three times, then release. Start the car and drive for 20 minutes at 25+ mph.

GM Vehicles (Chevy, GMC, Buick, Cadillac)

Most use a relearn procedure through the Driver Information Center (DIC). Navigate to "Tire Pressure" > "Relearn" and follow the prompts. You may need a TPMS relearn tool ($25-$50) that triggers each sensor.

Ford Vehicles

Newer Fords (2008+) often reset automatically once pressure is corrected. Older models may require a reset through the dashboard settings. Some need a specific sequence: key on, press the hazard button, then cycle each tire's pressure up and down.

Most Modern Vehicles (2015+)

Many newer cars allow TPMS reset through the infotainment touchscreen. Look in Settings > Vehicle > Tires or similar. Some cars with indirect TPMS (like certain BMWs) require you to select "Reset" after adjusting pressure and it recalibrates during driving.

What a Flashing TPMS Light Means

This is different from a solid TPMS light and people get confused. A flashing TPMS light (blinks for 60-90 seconds when you start the car, then stays solid) means the TPMS system itself has a problem — NOT necessarily that your tire pressure is low. Common causes:

• Dead sensor battery (most common on cars 7+ years old)
• Sensor damaged during tire service
• Sensor not recognized after installing new wheels or tires
• Interference from aftermarket electronics
• Spare tire with a sensor is mounted (some cars alert because the spare sensor ID doesn't match)

A flashing TPMS light requires a shop with a TPMS scan tool to identify which sensor has failed. You can still drive normally, but you won't have pressure monitoring on the affected wheel. For more on getting the right automotive help, check out the resources at APEX Tech Nation where working technicians share real diagnostic knowledge.

TPMS Sensor Replacement Costs

One tip that'll save you money: if you're getting new tires, have the TPMS service kits replaced at the same time. The tires are already off the rims so there's no extra labor. If your sensors are over 7 years old, seriously consider replacing all four while the tires are off.

According to NHTSA, properly inflated tires reduce the risk of tire-related crashes by a significant margin, and TPMS-equipped vehicles have far fewer under-inflation incidents than pre-TPMS vehicles.

Common Mistakes to Avoid

When to Call a Pro

You can handle the simple stuff — checking and adding air, visually inspecting for a nail or damage. Here's when you need a professional:

• Flashing TPMS light: You need a TPMS scan tool to identify which sensor failed.
• Light won't go off after correcting pressure: Could be a dead sensor, an internal leak not visible from outside, or a system that needs a relearn procedure your car doesn't allow from the driver's seat.
• Tire losing air with no visible damage: The leak could be at the bead (where tire meets rim), from a cracked valve stem, or from porous wheel corrosion on alloy rims. All require dismounting.
• After installing new wheels or tires: Sensors need to be relearned to the car. Some require OEM-level scan tools.

Any tire shop can handle TPMS work. Consumer Reports has good information on tire safety and shop recommendations. Dealerships charge more but will always have the correct OEM sensors. Good independent tire shops use quality aftermarket sensors that work just as well for less money.

The EPA notes that properly inflated tires also improve fuel economy — underinflated tires can reduce MPG by about 0.2% for every 1 PSI drop in the average pressure of all tires. It adds up over a year.