TPMS, or Tire Pressure Monitoring Systems, alert you if you have unsafe air pressure in any of your tires. These monitors are installed in your wheels, and alert you through a symbol on the dashboard that looks a little like a flat tire. In 2007, the Federal TREAD act (or Transportation Recall Enhancement, Accountability and Documentation) began requiring all new cars and light trucks come equipped with TPMS. This legislation, like that requiring air bags, helps to keep you safe on the road. The TPMS sensors are located inside each of your wheels. The sensors send a radio frequency signal to the vehicle onboard computer, which will illuminate a light on your dashboard if your tire pressure were to become unsafe. If you see that light activate and stay on, you'll want to pull over and check that your tires are okay. It's a good idea to carry a digital air pressure gauge for checks like these. As long as your tires are safe, you can drive on to a shop and have the air topped off. If the tire is punctured or flat, you can change it or call for roadside assistance. Driving on underinflated tires is dangerous. They create friction, heat up and can blow out while you're driving -- this causes thousands of accidents every year. Seventy-five percent of all roadside flats are caused by under-inflation. Under inflated tires also waste money. They lower your fuel efficiency up to 10 miles for every fill-up, costing money each time you go to the pump. Underinflated tires also degrade faster, sending you to the shop for a big ticket purchase earlier than necessary. If the light comes on and starts flashing, that means one or more of your sensors can't accurately measure your air pressure
. It's probably due to a low battery. The sensor battery life is about 5 to 7 years. Once the TPMS battery dies, the sensor itself needs to be replaced.