Tire Pressure Warning Light (TPMS) On: What to Do
The tire pressure monitoring system (TPMS) is required on passenger vehicles sold in the United States. The icon looks like a flat tire with an exclamation mark. It warns you when one or more tires are well below the recommended pressure, because low pressure hurts handling, braking distance, tire life and fuel economy.
Light on, steady
A steady light means pressure is low in at least one tire. Common reasons:
- Cold weather. Air pressure drops when the temperature falls, so the light often appears on the first cold morning of the season.
- A slow leak from a nail or screw, a damaged valve stem or a leaking wheel rim.
- Natural air loss. Tires lose a small amount of pressure over weeks even when they are healthy.
Light blinking, then steady
If the light blinks for about a minute after you start the car and then stays on, the system itself has a fault: a dead sensor battery, a damaged sensor or a communication problem. The tires may be fine, but the car can no longer warn you, so get it checked.
What to do
- Park safely and look at all four tires. If one is visibly flat, do not drive on it.
- Check the pressure of every tire with a gauge when the tires are cold. The recommended value is on the sticker in the driver's door jamb, not on the tire sidewall.
- Inflate to the recommended pressure. Do not forget the spare if your car has a sensor in it.
- Drive for several minutes. In most cars the light goes out by itself; some need a reset procedure from the manual.
- If the light returns within days, the tire is losing air. A tire shop can find the leak by submerging the tire or spraying soapy water, and can often repair a small puncture in the tread.
Sensor problems
The sensors sit inside the wheels and are powered by small batteries that eventually run out, typically after several years. After new tires, a tire rotation or a wheel change the sensors may also need to be re-learned. A shop with the right tool can read each sensor and replace the faulty one.
Do not ignore it
Driving on under-inflated tires overheats the sidewalls and can end in a blowout, especially at highway speed or with a heavy load. Find a nearby tire service, compare reviews and call ahead.