Learn Why Your Car's Low Tire Pressure Light Is On & What It Means

If you have noticed an illuminated exclamation point within a circle on your car's dashboard, your tires are trying to tell you something. This light is the tire pressure warning light, and it alerts you to low tire pressure levels to help prevent unsafe tire conditions.

Illustration of tire pressure warning light on a dashboard

Your vehicle's tire pressure light is located on the dashboard, and will illuminate if your tires have dropped 25% or below the manufacturer's recommended pressure level. The system that keeps the tires and your car's computer connected is known as the Tire Pressure Monitoring System, abbreviated TPMS.
TPMS is a convenience system, and many older vehicles were not equipped with this feature. Often, it is obvious when your tire pressure is low. You may notice the sidewall of the tire bulging slightly, or you might feel your vehicle pulling to one side. TPMS takes the guesswork out of tire pressure to keep you alert to the pressure levels in your tires, but it may not activate the warning light if your tires are only a few pounds of pressure low. Performing regular visual inspections of the tires and staying aware of how your vehicle drives is always your best defense against low tire pressure or tire damage.
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What is TPMS?

All US-manufactured vehicles produced after September 1, 2007 are equipped with a TPMS monitoring system, which monitors a vehicle's individual tire pressure and then alerts the driver to low pressure levels using the tire pressure light on the dashboard. Some cars have TPMS sensors that are attached to the inner rim of the wheel, whereas others are integrated into the valve stem that is used to inflate the tires. In either case, the TPMS sensors in each tire contain a battery and a wireless transmitter that communicates with the computer to relay tire pressure readings. If a sensor reads a low air pressure level, your vehicle's computer registers the low pressure reading and triggers the low tire pressure light. triggers the low tire pressure light.

Checking the tire pressure on his car

Once you notice the tire pressure warning light, you should inspect your tires to find the source of the problem. In some more modern or advanced TPMS systems, a display on your dash or overhead console may allow you to see which tire may be low, or can even show you the pressure in each of your tires. In older vehicles, the light may simply come on to alert you that one or more tires are low. You should first use a tire gauge to measure the pressure in each tire before adding any with air. This is done to determine which tire may be causing the light to illuminate and to prevent overfilling a tire, which can also be a safety hazard, or cause tire wear or damage. While filling the tire, be sure to periodically check the tire pressure to ensure you are not exceeding the manufacturer's air pressure recommendation. Once the tires are all within 25% of the recommended pressure, the TPMS warning light should turn off by itself.
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What To Do When Your TPMS Warning Light Is On

In some cases, you may find that all of your tires have adequate pressure, but your TPMS light is still on. This can indicate a problem with the TPMS sensors or TPMS module on your vehicle. In most cases, this will require professional diagnosis and service, and one or more TPMS sensors may need to be replaced. Though TPMS sensors can be replaced when a tire has been removed, a special electronic tool is also needed to program the sensor and allow the new sensor to pair with the computer and transmit a signal.

You may also find that your TPMS warning light turns on and off intermittently, which could be caused by a failing or worn TPMS sensor. In some cases, this can also be triggered by the ambient temperature and weather conditions. Cold temperatures are one reason why your TPMS light may be on, as cold air condenses, and denser air causes a decrease in pressure inside your vehicle's tires. You may see your tire pressure light turn off after driving a few miles in the winter, as the friction between the tires and the road causes heat and results in the air expanding and pressure inside the tires increasing. Want to learn more? We further explain the relationship between winter and the tire pressure light in this article.

Keeping your tires inflated properly is crucial to maintaining a safe vehicle, and deflated tires may not only suffer damage or premature wear, but can put you and others in danger. You can learn more about the dangers of driving with low tire pressure with help from our How Low Can You Go? Article. O'Reilly Auto Parts also has an array of educational videos and detailed instructions on How to Check Your Tire Pressure and How To Change A Flat Tire. If you're looking for an air pump for tires, tire pressure gauges, valve stem caps, or other tire tools and accessories, stop by your local O'Reilly Auto Parts or shop online to keep your vehicle driving safely. Maintaining the correct tire pressure to help prolong the life of your vehicle's tires, improve gas mileage, and decrease tire wear, while ensuring the safety of you and your passengers.


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