4 important things to know about your car's tire pressure gauge

The tire pressure sensor is a sensor that reads the pressure in all four tires on a vehicle. Modern cars have a built-in tire pressure monitoring system (TPMS). Beginning in 2007, the TPMS system must report 25 percent underinflation on any combination of all four tires.

Tire pressure indicator

The low tire pressure indicator comes on when the TPMS indicates a pressure below 25 percent of the manufacturer's recommended pressure. Light is indicated by an exclamation point surrounded by a "U". If this light comes on in your vehicle, it means that the tire pressure is low. You must find the nearest gas station to fill up your tires.

What to do if the tire pressure indicator lights up

If the TPMS light comes on, check the pressure in all four tires. It can be one or a pair of tires that need air. It's a good habit to check all tires to make sure they're filled to the manufacturer's standards. Also, if the pressure gauge at the gas station shows normal tire pressure, you may have a problem with the TPMS system.

Indirect and direct TPMS

Indirect TPMS uses the anti-lock brake system's wheel speed sensor to determine if one tire is spinning faster than the others. Because an under-inflated tire has a smaller circumference, it must roll faster to keep up with tires that are normally under-inflated. The error of the indirect system is large. Direct TPMS measures actual tire pressure to within one psi. These sensors are attached to the tire valve or wheel. As soon as it measures the pressure, it sends a signal to the car's computer.

The dangers of under-inflated tires

Under-inflated tires are the main cause of tire failure. Riding on under-inflated tires can cause tearing, tread separation and premature wear. Emissions can cause damage to the vehicle, passengers and others on the road due to debris and potential loss of vehicle control. According to the National Highway Traffic Safety Administration, thousands of injuries can be prevented every year if people inflate their tires to the correct pressure.

The tire pressure indicator will light up if your tires are under-inflated. Riding on under-inflated tires is dangerous, so it is important to inflate them immediately.