Tire Pressure Monitoring Systems (TPMS)
Tire pressure monitoring systems continuously monitor the pressure in the tires through sensors located in the tires (direct system) or the use of wheel speed and other vehicle sensors (indirect system). The information collected by the sensors is transmitted to an on-board processor that interprets the sensor signals and warns the driver when tire pressure is below the minimum acceptable level by illuminating a warning lamp.
The U.S. government, through the National Highway Traffic Safety Administration, requires that all passenger cars, light trucks and vans (Gross weight less than 10,000 pounds) be equipped with a TPMS starting in model year 2008. Due to a phase-in of the requirements, 20 percent of model year 2006 and 70 percent of model year 2007 vehicles are equipped with TPMS.
When the TPMS warning lamp on the instrument panel illuminates while driving, it means that the system has detected at least one tire with a pressure below the accepted minimum psi for the vehicle. The tires should be inspected and the tire pressure checked as soon as possible. The lamp will extinguish after the tires are properly inflated.
All TPMS installed on 2008 model year vehicles and beyond are required to detect and warn the driver when the system is not functioning properly (malfunction indicator). For some TPMS, a system malfunction is indicated by a flashing of the low tire pressure warning lamp for a period 60 to 90 seconds with the warning lamp remaining illuminated after the flash sequence.
There are two different low tire pressure warning indicators allowed by the federal standard. One icon is the cross-section of a tire with an exclamation mark inside. The other is a top view of a car with all 4 tires exposed.