What is TPMS and how does it work?

There are two main kinds of TPMS: direct and indirect. A direct TPMS measures tire pressure directly via a pressure sensor attached to the back of each tire’s valve. This sensor is battery powered and transmits data to the vehicle’s central computer. An indirect TPMS collects data from existing sensors, such as ABS and wheel speed sensors, which is then interpreted by software to infer the tire pressure. This kind of system makes use of the fact that low tires rotate at a different speed than correctly inflated ones. Either system will activate the tire pressure symbol on the dashboard when pressure falls significantly below the recommended pressure for the vehicle.

When the TPMS light is on, it most likely means the system is performing exactly as designed: alerting you that your tire pressure is outside the recommended range. You should manually check the tire with a gauge and inflate the tire to the manufacturer’s recommended level if the pressure is low.

If the light is on but you find that the tire pressure is correct, the system may be malfunctioning. Another possible sign of a bad sensor is a TPMS indicator light that blinks when you start your car and then remains on. Temperature can also affect tire pressure, so if the TPMS light is alternating on and off, it may be that excessive heat or cold is pushing the pressure beyond the recommended values.

If your TMPS light is on, you should always assume your tire is underinflated and check it as soon as possible. Underinflated tires do not perform correctly and can lead to blowouts, loss of control, and poor handling. They are the cause of thousands of accidents per year in the United States alone, so it’s an issue that shouldn’t be taken lightly. If you check your tire pressure and none of your tires are low, it may be okay to keep driving slowly and carefully with the TPMS light on, but you should fix the problem as quickly as possible at your nearest service shop.

A tire pressure sensor’s price tag will depend on your car model and the part it requires. It is generally necessary to replace the sensor and the batteries together—they are usually a single unit. For the part and labor, you can expect to pay anywhere from $75 per sensor to over $200, depending on your vehicle.

Yes, TPMS have been a required safety feature (under the TREAD Act in the US) since 2008.

TPMS sensors most often need to be replaced because their batteries have reached the end of their 5- to 10-year lifespan, although they could be damaged sooner by road conditions. Most sensor models have built-in, non-replaceable batteries, so the only solution is to replace the whole sensor. In some instances, problems with the valve stem can be fixed without putting in a whole new sensor unit.

You should always try to keep your tires inflated to the pressure recommended by your vehicle manufacturer. When tires are operated at improper pressures, the tire’s sidewalls can flex and damage the belting structure in the tires. You will not be able to see this damage, which can increase over time. This is why you should maintain proper inflation pressure and try to avoid driving when the TPMS light is on. If you absolutely must drive a short distance on a tire with severely low pressure, drive very slowly and use extreme caution. The tire should be inflated or changed before driving anywhere.

If you still have questions about your TPMS or suspect your system or tires are not functioning properly, get help from your nearest tire dealer so you can stay safe on the road