Your tire monitor system watches air pressure and alerts you when a tire is underinflated
A tire pressure monitoring system (TPMS) is a sensor in each of your tires that measures how much air is inside and sends that information to your dashboard. When one or more tires drop below the safe pressure level for your vehicle, a warning light turns on — usually a picture of a tire with an exclamation mark. The system does not fix the problem; it only tells you one exists so you can address it.
Most vehicles sold in the United States since 2008 have TPMS as standard equipment. The system runs constantly while you drive, checking pressure every few seconds. Some systems also monitor temperature, which can help catch a tire that is overheating before it fails.
The reason manufacturers installed TPMS in every car is straightforward: underinflated tires wear out faster, use more fuel, and are more likely to blow out. A tire that is even 10 pounds per square inch (PSI) below the recommended pressure can reduce fuel economy and shorten tire life. TPMS catches this problem before you notice it yourself.
Key Takeaways
- TPMS sensors measure air pressure inside each tire and send alerts to your dashboard when pressure drops below the safe range for your vehicle.
- The warning light means you should check your tire pressure and add air, not that your tire will fail when ready, but underinflated tires do wear faster and use more fuel.
- TPMS sensors run on batteries that typically last seven to ten years, and replacing a sensor costs between $50 and $200 per tire depending on your vehicle.
- Temperature changes, especially in cold weather, can trigger the warning light even if your tires are not actually leaking, because air contracts when it cools.
How the sensors work and what they measure
Each tire has a small sensor mounted inside the wheel, either on the valve stem or on the wheel rim itself. The sensor contains a battery, a pressure gauge, and a transmitter. As you drive, the sensor takes pressure readings and sends them wirelessly to a receiver in your vehicle's computer system.
The system compares the pressure in each tire to the target pressure for your vehicle — this number is printed on a sticker inside your driver's door frame, not on the tire itself. If any tire falls 25 percent below that target (the exact threshold varies slightly by manufacturer), the warning light activates. Some systems also show you the pressure reading for each tire on your dashboard screen.
There are two types of TPMS: direct and indirect. Direct TPMS uses the physical sensors described above and is more accurate. Indirect TPMS uses your vehicle's anti-lock brake system to estimate tire pressure by measuring how fast each wheel spins — a flat tire spins faster than a properly inflated one. Indirect systems are less expensive to install but cannot tell you the exact pressure in each tire.
When the warning light turns on and what to do
The TPMS light usually appears as a yellow or amber tire symbol on your dashboard. It may say "Check Tire Pressure" or straightforward show the tire icon. This light means at least one tire is underinflated and needs air. It does not mean your tire is damaged or that you are in when ready danger, but it does mean you should address it soon.
Your first step is to check the pressure in all four tires using a tire pressure gauge. You can buy a basic gauge at any auto parts store for under $10, or use the free air pump at most gas stations, which usually has a built-in gauge. Compare your readings to the target pressure on the door frame sticker. Add air to any tire that is below the target.
If the light stays on after you have inflated all tires to the correct pressure, one of your sensors may be faulty, or you may have a slow leak. A slow leak means air is escaping from the tire over time — this is different from a flat tire and often cannot be seen by eye. Take your vehicle to a tire shop or mechanic to locate the leak and repair it, or to replace a faulty sensor.
Why the light comes on in cold weather
One of the most common reasons the TPMS light turns on is a drop in outside temperature. Air contracts when it gets cold, which means the pressure inside your tires drops even if there is no leak. For every 10 degrees Fahrenheit the temperature falls, tire pressure drops roughly 1 PSI.
This is not a malfunction — it is how air behaves. If your light comes on overnight or during a cold snap, check your tire pressure and add air if needed. As the tires warm up from driving and the outside temperature rises, the pressure will increase again, and the light may turn off on its own. This is normal and does not indicate a problem with your tires or your TPMS.
If the light comes on repeatedly during cold months but your tires are at the correct pressure, your TPMS is working as designed. You can prevent this by checking your tire pressure before winter arrives and inflating to the target pressure when temperatures are mild.
TPMS sensor batteries and replacement costs
The battery inside each TPMS sensor is not replaceable — when it dies, you must replace the entire sensor. Most TPMS batteries last between seven and ten years, though some last longer and some fail sooner depending on how often the sensor transmits and the quality of the battery.
Replacing a TPMS sensor typically costs between $50 and $200 per tire, depending on your vehicle make and model and whether you go to a dealership or an independent shop. Some vehicles have sensors that are easier to access and cheaper to replace; others require more labor. When you replace a tire, the shop should also replace or reprogram the sensor in that wheel.
If multiple sensors fail at once, or if you are replacing all four tires, ask the shop whether it makes sense to replace all four sensors at the same time. Doing so at once is often cheaper than replacing them one at a time over several years.
What to do if your TPMS light stays on
If you have checked all four tires, inflated them to the correct pressure, and the light is still on, the problem is likely a faulty sensor, a slow leak, or a sensor that needs to be reprogrammed. Do not ignore the light — it is telling you something needs attention.
Take your vehicle to a tire shop or mechanic and describe what you have already done. They can use a TPMS diagnostic tool to read the sensor data and identify which tire or sensor is causing the alert. If it is a slow leak, they can patch the tire or recommend replacement. If it is a faulty sensor, they can replace it and reprogram the system.
Some vehicles also have a TPMS reset button, usually located under the steering wheel or in the glove compartment. Consult your owner's manual to see if your vehicle has one. Pressing the button after inflating your tires can sometimes clear the light if the sensors just need to recalibrate to the new pressure.
Frequently Asked Questions
Can I drive with the TPMS light on?
Yes, you can drive with the light on, but you should not ignore it. An underinflated tire will wear faster and use more fuel, and a severely underinflated tire can overheat and fail. Check your pressure and add air as soon as you can, or have the tire inspected if you suspect a leak.
Does TPMS work in all weather?
TPMS works in all weather, but cold temperatures will cause the light to come on even if your tires are not leaking. This is normal. Warm weather can also affect readings, though the effect is smaller. Always check your actual tire pressure with a gauge rather than relying only on the warning light.
What if one sensor keeps failing?
If a sensor in the same tire fails repeatedly, the problem may be with the valve stem, the wheel, or the tire itself. A mechanic can diagnose whether the sensor is defective or whether something else is causing it to malfunction. Replacing just the sensor may not solve the problem if the underlying cause is not addressed.
Do I need TPMS if I check my tires regularly?
TPMS is a safety backup, not a replacement for regular tire checks. Checking your pressure monthly with a gauge is still a good habit because it catches problems TPMS might miss, like a tire that is overinflated or a slow leak that has not yet dropped pressure enough to trigger the warning light.