A. It depends on the age of the sensors. By the time the tires are worn out, the TPMS sensors may be nearing the end of their useful service life or they may not have enough remaining battery life to last another set of tires.
The lithium ion batteries inside TPMS sensors may last anywhere from five to 10 years. Five to six years is a more typical lifespan for older TPMS sensors. TPMS sensors don’t broadcast a continuous signal but only broadcast when the vehicle is in motion. Even then, the signal is intermittent to conserve battery life.
On most applications, the battery is molded into the TPMS sensor assembly so it cannot be replaced separately. Consequently, if the battery is run down or dead, the entire TPMS sensor has to be replaced at a cost that may range from $50 up to $150 or more depending on the application and type of sensor.
Though TPMS has been around since the early 1990s and has been mandatory on new vehicles since 2008, there’s been little or no standardization of original equipment TPMS systems or sensors.
Fortunately, several aftermarket suppliers have introduced “universal” TPMS sensors that can replace more than 100 different OEM sensors with only a few SKUs and at less cost than the OEM sensors. These sensors reduce inventory requirements and can be easily programmed to the vehicle application. Universal replacement TPMS sensors are available with clamp-in (nut at the base of a metal valve stem) and snap-in (rubber) valve stems. These can even be used to replace many of the older “band” style TPMS sensors that are clamped inside the drop center of the wheel.
When TPMS sensors are replaced (either individually or all four at the same time), or when the tires are rotated, the vehicle’s tire pressure monitoring system has to relearn the wheel location of each sensor. On some newer vehicles, this function occurs automatically when the vehicle is driven. But on most of the older applications, there is a specific learning procedure that must be performed before the TPMS system will operate correctly. Some of these procedures can be rather lengthy and must be followed exactly otherwise the TPMS system may not learn the correct wheel locations. Many of these procedures require using a magnet or special TPMS service tool to activate the sensors during the relearn procedure. Some applications may even require a scan tool to enter sensor ID information into the TPMS system.
Q. What can cause a TPMS sensor to fail prematurely?
A. Corrosion has been an issue with some original equipment TPMS sensors that have a nut at the base of the metal valve stem (snap-in style TPMS sensors with rubber valve stems are not subject to this type of corrosion). Exposure to road salt and moisture promotes galvanic corrosion that weakens the metal valve stem. Eventually, this can lead to failure of the valve stem, causing a sudden loss of air pressure from the tire (the very problem TPMS was supposed to prevent).
Using some types of aerosol tire sealer/inflator products may also cause sensor problems if the sealer gums up the TPMS sensor. Recommend a product that is “TPMS safe.”
Q. Does the law require replacing a bad TPMS sensor?
A. It depends on the situation. There is no legal requirement (yet) at the national level to replace a bad TPMS sensor if the TPMS warning light is on or flashing. That’s a decision the vehicle owner has to make regarding their own safety. Obviously, if a TPMS system has one or more bad sensors, it can’t warn the motorist of a low tire.