The TPMS will illuminate a dashboard warning light whenever the pressure drops below the vehicle's recommended level by 25% or more. The official TPMS symbol is a yellow exclamation mark inside a tire cross-section. If you see this alert illuminated on the dash, you should immediately check your tire pressure or stop by one of our stores so we can inspect your tire for a puncture that might be causing the air loss. If the light still displays after setting the tire pressure, your TPMS may need to be run through a "relearn" process or might even require a TPMS sensor replacement.
One of the significant safety advantages is to help prevent underinflated tires from growing into larger problems. Additionally, the TPMS can help you address changes in temperature that cause fluctuations in tire pressure. Responding to your TPMS and keeping your tires properly inflated can increase fuel efficiency, extend tire life and contribute to your vehicle’s stability and safety.
Types of TPMS - Direct or Indirect
The types of TPMS can vary by the system your vehicle is equipped with; direct or indirect. Each type of system uses different mechanical set-ups and methods to monitor tire pressure and alert you when the air pressure is low. Direct TPMS measures air pressure through dedicated sensors attached to the wheel (rim), while indirect TPMS estimates low pressure based on tire rotation speed.
A direct TPMS uses battery-operated sensors attached inside the wheel to communicate with the vehicle. The sensors directly read the pressure in each tire and transmit the data to the vehicle computer. The system will trigger the dashboard light if a tire's pressure drops below 25% of the recommended inflation from the vehicle manufacturer. This process gives a direct TPMS a greater degree of accuracy than indirect TPMS. Some advanced direct systems even allow the driver to check individual tire pressures from the dashboard.
The direct TPMS system has a variety of sensors that are each designed for your specific vehicle and trained to communicate with your onboard computer. The sensor is located inside the wheel and can be a variety of TPMS sensor types depending on your vehicle. Learn more about TPMS sensors and rebuild kits.
An indirect TPMS estimates an underinflated tire through wheel speed sensors used by the anti-lock brake system. These sensors measure the rotational speeds of each tire. They can detect when one tire rotates faster than the others, which means the faster tire is low on pressure. If the system determines that a tire has low pressure, it will illuminate a dashboard light to alert you.
Automakers developed indirect TPMS to comply with federal regulations while reducing vehicle costs. These systems are cheaper to produce because they utilize existing vehicle components, but they have distinct disadvantages. An indirect TPMS cannot tell the driver which tire needs inflation and needs calibration after any service including a tire change or air pressure adjustment to ensure system accuracy.
TPMS Sensor Batteries
TPMS batteries last approximately 6-10 years or 90,000 to 120,000 miles. Tire sealant, corrosion from the elements and a weak or dead battery can make sensor replacement necessary. The battery inside the TPMS sensor is not removable. When the battery life has come to an end, a new TPMS sensor will be required. The TPMS sensor will need to be installed by a tire professional so that the system can be trained to recognize the new sensor. If one of the batteries in your TPMS has ended, it is likely the others are very close to needing replacement as well. It may be a good time to replace all of your sensors to eliminate any other TPMS related issues shortly down the line.
TPMS and Air Pressure Checks
The TPMS provides valuable assistance in monitoring your tire pressure, but should never replace your monthly air pressure check. Both types of TPMS will only alert you when the tire pressure drops below the vehicle's recommended pressure by 25%. This is a high threshold, as tires that are underinflated by just 5% begin to suffer from decreased fuel economy and increased internal temperatures. These issues become more pronounced as underinflation increases, so your tires can be underinflated without triggering a TPMS alert.
For this reason, you should never rely solely on TPMS to monitor tire pressure. You should always use a reliable gauge to manually check your tire pressure each month. The TPMS should function as a warning that complements your existing routine, not as your first line of defense.
If you have any questions or need any assistance, stop by your local America's Tire and we'll get you taken care of.