TPMS Warning Light The Tire Pressure Monitoring System (TPMS) is an electronic system that alerts the driver when the car’s tire pressure has fallen below an acceptable level of inflation by means of a dashboard warning light. The purpose of the TPMS is to improve vehicle handling, increase road safety and fuel economy, and decrease stopping distance and tire tread wear.
Since the National Highway Traffic Safety Administration (NHTSA) enacted the TREAD Act of 2008, a mandate that all vehicles be equipped with a TPMS, most Volvos, Saabs, Subarus and Minis have opted toward a direct TPMS, which uses a wheel-mounted sensor that measures air pressure. When air pressure drops 25% below the manufacturer’s recommended level, the sensor tells your car’s computer and triggers the dashboard warning light.
Another possible option, which we see on vehicles manufactured before the technology was mandatory is the indirect TPMS, which works with the Antilock Braking System’s (ABS) wheel speed sensors to determine whether a tire’s pressure is low, since an under-inflated tire will have a different wheel speed than a properly inflated tire. This information is detected by your car’s computer system, which triggers the dashboard indicator light.
If you are not sure whether your car is equipped with TPMS, turn the key to the “on” position and see whether a “low tire pressure” warning light appears on your dash. The presence or absence of this indicator light tells you whether or not your car has TPMS.
Pumping Up an Under-inflated Tire (Subaru) Regardless of whether your vehicle is equipped with a direct or indirect TPMS, when your TPMS dash warning light is illuminated, it is giving you important information about your current tire pressure, and checking tire pressure is a priority, which you can do yourself, or we can do for you.
Inflate your tires to the manufacturer’s recommendation. When the tire is at the appropriate pressure, the indicator light should go off within three miles of driving. If you have corrected the tire pressure and the dash warning light is still illuminated, this could indicate a problem with the TPMS.
Although there are obvious safety benefits to this feature of your vehicle, there are less obvious maintenance costs. The valve service kit, which includes the valve core, cap, nut and o-ring (seal), must always be replaced when a tire is dismounted for service or replacement. A special TPMS tool and extra time are needed to check and reset the sensor system.
Follow this link to see a video regarding the National Highway Traffic Safety Administration (NHTSA) TREAD Act and TPMS.
Dash indicator from www.cars101.com/subaru/dashboard.html
P hoto by Flickr user Rich Moffitt