There are two types of tire pressure monitoring systems. The first, and most popular, is the direct TPMS. Direct TPMS uses pressure sensors located in each wheel. Each sensor measures the real-time pressure in its respective tire, warning you when the air pressure in that tire drops at least 25% below the recommended cold tire inflation pressure.
The second is an indirect TPMS. This system does not use physical sensors but instead measures the air pressure and bases its warnings upon monitoring the velocity of the tires. An under inflated tire has a smaller diameter than a properly inflated tire so it has to rotate faster to cover the same ground as the properly inflated tires.
A direct TPMS includes five service parts: a valve core, valve nut, valve cap, seal, and seal washer. These parts are fragile and can be easily damaged over time or when you replace your tires. It is important to keep the sensor operating and extend its life by replacing and/or servicing damaged parts. An Automotive Service Excellence (ASE) Certified technician is trained to diagnose and service any problem with your TPMS.
The sensors are designed to outlast the life of your tires and since the TPMS sensors are attached to the wheel itself, every time a tire is removed it is recommended the valve cap, valve core, valve nut and seal washer be replaced with original equipment (OE) specification parts. The main cause of valve leaks is from old and damaged rubber grommets so they must be replaced when reinstalling a sensor.
The most common problem with direct TPMS is the loss of response from any one of the sensors. This usually occurs if the sensor’s lithium battery, with a life expectancy of five to ten years, dies or if the transducer or transponder stops working. The older a vehicle is the more likely it is that a sensor will fail. Typically, if the TPMS light is blinking on your dashboard it means there is a problem with the system.
A repair shop will not disable a TPMS low-pressure warning signal upon request because it is illegal to do so. No law dictates that every sensor has to be functioning or that the TPMS must be repaired if it is malfunctioning. It is not recommended however, that drivers operate their vehicle without this system in proper working order. A well working TPMS will alert you to low-pressure on the first occurrence so that it can be fixed to keep you safe and to keep your tires from wearing prematurely.
If your car does not have a TPMS, your local tire discount store can install a portable direct system in your vehicle. The system’s individual sensor in each tire monitors tire pressure, temperature and other important data and alerts you when a problem arises through a dashboard transmitter.
Although a TPMS indicates to you low tire pressure as soon as it occurs, it is still strongly recommended that you manually check your tire pressure at least once a month and always before a long trip. Low tire pressure can cause tire stress, uneven tire wear, loss of control and accidents. Keep you and your passengers safe by properly maintaining your current TPMS or by installing a portable TPMS at your local tire discount store.