# What is TPMS on a car? ## Quick answer TPMS, or tire pressure monitoring system, warns the driver when one or more tires are significantly underinflated. ## What is TPMS? TPMS stands for tire pressure monitoring system. It has been required on new passenger vehicles in the US since the 2008 model year. When a tire is well below the recommended pressure, it turns on a warning light shaped like a tire cross-section with an exclamation mark. Under the federal rule, the light must come on when a tire is 25 percent or more below the recommended cold pressure. Direct TPMS uses a pressure sensor inside each wheel. Indirect TPMS uses the ABS wheel speed sensors, since a low tire turns slightly faster than the others. Direct systems can often show each tire's pressure on the dashboard, while indirect systems usually show only a warning and need a reset after you adjust pressures. Direct sensors run on sealed batteries that eventually wear out, and the sensor is usually replaced as a unit. After a tire rotation, new tires or a new sensor, some cars relearn sensor positions automatically, while others need a relearn procedure or a TPMS tool. Your owner's manual explains the steps. The system is a warning, not a replacement for checking pressure. Check your tires monthly with a gauge, using the pressure on the driver's door jamb label. A tire can lose a lot of pressure before the light comes on, and cold weather often triggers the light on the first cold morning. A flashing TPMS light usually means a system fault. ## How it works 1. Direct systems have a battery-powered sensor in each wheel that sends pressure readings by radio. 2. Indirect systems compare wheel speeds, because a low tire is smaller and spins faster. 3. When a tire drops well below its recommended pressure, the car turns on the TPMS light. 4. If the light flashes for about a minute and then stays on, the system itself has a problem. ## Types of TPMS | Type | What it is | | --- | --- | | Direct TPMS | A battery-powered sensor in each wheel, usually attached to the valve stem, sends pressure readings by radio. | | Indirect TPMS | Uses ABS wheel speed sensors to spot a tire that spins faster because it is low; no sensors in the wheels. | | Sensor relearn | The process that teaches the car each sensor's ID or position after rotation or replacement; methods vary by maker. | | Warning light modes | A steady light means low pressure, while a light that flashes for about a minute and then stays on usually means a system fault. | ## Common TPMS problems - Low tire pressure from a slow leak, nail or damaged valve stem. - Pressure dropping in cold weather, often turning the light on during the first cold mornings. - A direct sensor with a dead battery, often after several years. - A corroded or damaged sensor or valve stem, sometimes found during tire service. - Sensors not relearned after rotation or new tires, causing warnings or wrong positions. ## Frequently asked questions ### Why is my tire pressure light on when my tires look fine? Tires can be low without looking flat, and cold weather lowers pressure, roughly 1 psi for every 10 degrees Fahrenheit. Check each tire with a gauge when cold and fill to the pressure on the door jamb label, not the maximum on the sidewall. The light may take a short drive to go off. ### What does a flashing TPMS light mean? A light that flashes for about a minute and then stays on usually means a system fault, such as a dead sensor battery, a damaged sensor or a sensor that was not relearned. The system may not warn you about low pressure until it is fixed. Have a tire shop check the sensors. ### How long do TPMS sensors last? Many direct TPMS sensors last around 5 to 10 years before their batteries run down, depending on driving and climate. The battery is usually sealed inside, so the whole sensor is replaced. They are often replaced when tires are changed on an older car to save labor. ### How do I reset the TPMS light? First set all tires to the pressure on the door jamb label. Many direct systems turn off after a short drive. Indirect systems and some direct systems need a reset button or a menu setting, and some need a relearn tool. Check your owner's manual for your vehicle's steps. ### Is it safe to drive with the TPMS light on? Check the tires as soon as you safely can. Driving on a badly underinflated tire can overheat it, damage it and make the car harder to control. If a tire is visibly flat or the pressure is very low, change to the spare or call for help instead of driving on it. ### How much does a TPMS sensor cost to replace? Prices vary by vehicle and sensor type, and the job usually includes the sensor, labor to dismount the tire and a relearn. Replacing sensors while the tires are already off for new tires saves on labor. Ask whether the quote includes the relearn and valve service kit. ### Does the TPMS light come on for high pressure? Usually not. The federal requirement is for warning about low pressure, though some vehicles also alert for high pressure or show each tire's reading. Overinflated tires reduce grip and wear unevenly, so always set pressure to the door jamb label. ### Do I need TPMS sensors in my winter tires? If your car uses direct TPMS, winter wheels need their own sensors or the light will stay on. Many shops sell winter wheel packages with sensors installed and can program them. Indirect systems work with any wheels after a reset. ### Why does my TPMS light come on in the morning and go off later? Tire pressure drops overnight as the air cools, and if a tire is close to the warning threshold, the light comes on. As you drive, the tires warm up and pressure rises, turning the light off. Add air to the correct cold pressure to stop it. ### What is the difference between direct and indirect TPMS? Direct TPMS uses a pressure sensor in each wheel and can often show actual pressures. Indirect TPMS uses ABS wheel speed sensors to detect a tire that spins faster because it is low. Indirect systems have no sensor batteries but need a reset after pressure changes. ## Sources - [NHTSA: Tire pressure monitoring systems](https://www.nhtsa.gov/equipment/tires#tire-pressure) ## Related terms - [ABS](https://diagxcar.com/glossary/abs) - [Traction control](https://diagxcar.com/glossary/traction-control) ## Related pages - [Tire pressure (TPMS) light](https://diagxcar.com/warning-lights/tire-pressure) - [How long do tires last?](https://diagxcar.com/how-long/tires): 40,000-60,000 miles - [What causes uneven tire wear?](https://diagxcar.com/symptoms/uneven-tire-wear) --- Source page: https://diagxcar.com/glossary/tpms Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.