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TPMS Made Simple Sponsored by Schrader

Frequently Asked Questions

What is TPMS?
Direct TPMS is a warning system that warns a vehicle's operator of an unsafe change in the air pressure in one or more of the tires. Readings are provided by pressure sensing transmitters mounted inside each tire and sent to a central computer (ECU) for display on the dashboard. A warning indicator light on the instrument panel and an audible warning notify the driver if a 25% drop in pressure occurs.

How do I know if my vehicle is equipped with TPMS?
In the U.S., if you purchased a car or light duty vehicle under 10,000 lbs, manufactured after September 1, 2007, you have TPMS. If your model was manufactured after October 5, 2005, you may have TPMS. Also, prior to the legislation, some higher-end vehicles also came equipped with TPMS as a premium option. Among other matters, within TREAD Act of 2000, the U.S. federal government mandated the required implementation of TPMS on all new vehicles in the following phased rollout:

  • 20% of new vehicles from Oct 5, 2005–Aug 31, 2006
  • 70% of new vehicles from Sept 1, 2006–Aug 31, 2007
  • 100% of new vehicles from Sept 1, 2007 and beyond
There are several ways to determine if your vehicle is equipped with TPMS. The easiest include checking the owner's manual and watching the dashboard indicator lights at startup. Turn the vehicle ignition switch to the "ON" or "AUX" position, or simply start the vehicle. Look for a TPMS warning light on the dashboard that looks like one of the TPMS displays pictured here.

Will my owner's manual tell me about TPMS?
Learn what the TREAD Act requires your Owners Manual to include about TPMS. Download What's In My Owner's Manual?

Can the TPMS system be bypassed?
No. Under 49 U.S.C. 30122(b), "A manufacturer, distributor, dealer or motor vehicle repair business may not knowingly make inoperative any part of a device or element of design installed on or in a motor vehicle or motor vehicle equipment in compliance with an applicable motor vehicle safety standard."

Since TPMS systems use Radio Frequency (RF) technology to transmit pressure data, is it possible they could be hacked or "fooled"?
Direct TPMS systems utilize radio frequency (RF) technology to transmit pressure data and other information to the vehicle's electronic control unit (ECU). RF-based TPMS systems provide a reliable and safe indication of tire pressure to the driver. The likelihood of an unscrupulous individual(s) creating a situation where they would hack into a sensor and "fool" the TPMS system is extremely unlikely, as is a scenario where a driver's location could be intercepted and identified. Direct TPMS systems, like Schrader's, are embedded in millions of vehicles in the U.S. and globally, operating as intended and keeping drivers safe. See Schrader's technical response on the RF-security topic. For more information, go to the "Wireless Security" page or read the Modern Tire Dealer article "Fear not: Wireless car hacking through the TPMS is extremely unlikely."

What is the TREAD Act?
Congress passed the Transportation Recall Enhancement, Accountabil–ity and Documentation (TREAD) Act in 2000. The TREAD Act, among other matters, requires new passenger cars, light trucks and buses to be equipped with a tire pressure monitoring system (TPMS), and requires notification of the National Highway Traffic Safety Administration (NHTSA) in all accidents involving alleged tire defects. Read more about the TREAD ACT.

What does the TREAD Act require regarding TPMS?
The TREAD Act (and its subsequent enforcement statue 49 CFR 571.138, commonly known as Federal Motor Vehicle Safety Standard 138 (FMVSS 138), requires original car manufacturers to equip all new vehicles with:

  • Monitoring of tire pressure in all four tires. Monitoring the spare is not required
  • A TPMS system that operates when the vehicle ignition is on and warn when tires are underinflated by 25% or more
  • A TPMS system that alerts the driver when there is a system malfunction
  • A TPMS warning light that stays on until the tire is inflated to the proper pressure or the system malfunction is corrected
  • A "bulb check" of the warning light on the instrument panel that occurs whenever the ignition is turned on
  • Vehicle owner's manuals that contain warnings about potentially incompatible replacement tires for the vehicle

What vehicle types does the TREAD Act cover?
The TREAD Act/FMVSS 138 covers mostly all passenger vehicles including light duty vehicles under 10,000 lbs gross vehicle weight, and including certain trucks and buses. However, the regulation does not cover motorcycles and light duty vehicles with dual wheels on an axle.

How does tire pressure affect my safety?
As most drivers check their tires only at service intervals and when problems occur, motorists can benefit greatly from a greater awareness of tire pressure and its effects on safety while driving. The National Highway Traffic Safety Administration (NHTSA) has estimated that 660 U.S. automobile accident fatalities annually are caused by underinflated tires. Dry and wet surface handling suffers with underinflated tires, including:

  • Skidding and loss of control of the vehicle in a pronounced curve, such as an off-ramp from the highway, or when taking any curve at a high speed
  • Hydroplaning on a wet surface, which can affect both stopping distance and skidding or loss of control
  • Crashes from flat tires or blowouts

What exactly does it mean when my TPMS warning light comes on?
If the TPMS warning light comes ON and flashes ON for one second and OFF for three seconds, this indicates a malfunction with the vehicle's TPMS system.

If the TPMS warning light comes ON and stays ON, take caution. This means that one or more of your tires may have a low-pressure condition. You should carefully slow the vehicle and park in a safe and secure place. You should then inspect all of your tires and check the air pressure. The correct air pressure for your vehicle can be found on the placard, usually located on the inside door panel. Read more about what to do when you see the TPMS warning light.

Why does tire pressure change?
Many factors affect tire pressure including ambient temperature changes and tire damage such as punctures. Tire pressure drops about 1 psi for every 10°F drop in ambient temperature. Additionally, tires can lose as much as 1.5 psi per month as air escapes the tire and rim naturally.

What should my tires be inflated to and where can I find that?
Tires should be inflated to the vehicle manufacturer's recommendation as found on the vehicle tire information door placard. The vehicle placard is normally located on the inside door panel or door itself. In many cases the specified tire pressure can also be found in the vehicle owner's manual. The pressure indicated on the sidewall of the tire should not be your guide, as that is the maximum inflation pressure for the tire itself, not for the tire when used on your specific vehicle.

What does placard mean?
The tire placard is a term used for the tire information label. It contains information including the vehicle manufacturer's recommended tire pressure for your vehicle, the recommended tire size and the maximum load you should have in your vehicle. The placard is normally located inside the driver's side doorframe or doorpost, or it may be adhered to the edge of the driver's door or the inside of the glove box door or trunk lid. The same information is also located in your owner's manual.

What do I do when my TPMS light comes on during cold weather?
Does this really mean my tires are low? Any time that the TPMS warning light comes ON, there is a possible low tire pressure condition. Tire pressure can drop due to cold conditions, and this drop in pressure may cause the TPMS light to come ON. As the tire warms up under normal driving conditions, the light may turn OFF. If the cold weather conditions cause the TPMS light to stay ON, check the tire pressure (when tires are cold) and inflate the tire to the proper pressure indicated on the door placard.

Can having TPMS in my car really save me money?
Yes, properly inflated tires save money at the pump due to better fuel efficiency. According to FuelEconomy.gov, a joint Web site of the U.S. Department of Energy (DOE) and the Environmental Protection Agency (EPA), underinflated tires can lower gas mileage by 0.3% for every 1 psi drop in all four tires. Additionally, properly inflated tires are safer and last longer. The DOE and EPA highlight that fuel economy has four main benefits to you:

  • Saving money
  • Reducing fuel consumption and oil dependence costs
  • Reducing climate change
  • Increasing energy sustainability
According to the DOE, 3.56 million gallons of gas are wasted each day because of incorrectly inflated tires. The DOE asserts that motorists can improve gas mileage by approximately 3.3% by keeping tires inflated to the proper pressure. For most consumers, that represents approximately 10 additional miles or more on each tank of gasoline.

Can TPMS reduce my carbon footprint?
Small contributions by many can make a big difference in total. Properly inflated tires have a positive environmental impact by releasing less carbon dioxide (CO2) into the atmosphere through better gas mileage and fuel efficiency. A reduction in CO2 emissions contributes to reducing greenhouse gas emissions. According to the Environmental Protection Agency, Americans drive an average of 12,000 miles a year. With an average of 20 pounds of CO2 emitted per gallon of gasoline consumed, the typical passenger car in the U.S. releases over five tons of CO2 into the atmosphere each year. By improving the gas mileage of your vehicle, you can greatly reduce your carbon emissions and overall impact on the environment.

My car has TPMS. I haven't had it serviced yet at my repair facility. What should I expect when I get there?

  • Verification that your TPMS sensors and system are functioning properly
  • Service or replacement of any nonfunctioning component of your TPMS sensors
  • Replacement of TPMS sensor sealing components (cap, core, grommet and nut)
  • A "relearn" of your TPMS sensors to your vehicle's computer to program correct positioning of TPMS sensors
  • Verification that your TPMS system is functioning properly after tire service is complete

What if I have an extra set of tires and wheels (for snow tires or custom wheels)?
You can purchase a set of replacement sensors and have them installed in your extra set of tires or wheel assemblies. When the extra set of tires or wheel assemblies is mounted to the vehicle, your TPMS installer will have the ability to relearn the new sensors to the vehicle computer. When the original set of tires or wheel assemblies is reinstalled on the vehicle, the sensors will need to be relearned to the vehicle computer.

What if I have a roadside flat and try to plug the hole using off-the-shelf tire sealant?
Any time that a substance other than tire service center air or nitrogen is introduced into the tire, there is the potential to damage the TPMS sensor in the tire. However, if tire sealant has been used, your local TPMS installer can assess the sensor functionality and determine if the sensor is working properly or if it needs to be repaired or replaced.

Why does tire maintenance with direct TPMS cost more?
TPMS-equipped tires cost slightly more to maintain than non-equipped tires because servicing TPMS requires extra parts, tools and labor. The TPMS valve service kit, which includes the valve core, (sealing) cap, nut and grommet (stem seal), must be replaced whenever a tire is dismounted for service or replacement. The service kit costs an average of $5 to $10 per wheel on most vehicles. A special TPMS programming tool and additional time are also needed to check and reset the TPMS system. In the event TPMS sensors need to be replaced, the cost can range from approximately $50-$100 each depending on vehicle type.

As a manufacturer of original equipment TPMS sensors, Schrader® recommends that a service pack be used to replace the sealing components of the sensor, which includes the cap, valve core, grommet, nut and any other accessory supplied in the service pack. Replacing the service pack items ensures the integrity of the TPMS sensor and valve.

If my TPMS light comes on and I put air in my tires, will the light go off by itself or do I need to take my car to the dealer or a tire shop?
When the TPMS warning light comes ON and flashes ON for one second and OFF for three seconds, this indicates a problem with the vehicle's computer and can be corrected only by the dealership service center. When the TPMS warning light comes ON and stays ON, this indicates a low tire pressure condition in one or more tires. Inflating the tire to the recommended tire pressure found on the door placard should cause the light to turn OFF. Remember that one or more of the tires may be low in pressure, so you should always check the pressure in all of your tires.

Will the TPMS light come on if my tires are overinflated?
Not necessarily. The TREAD Act/FMVSS 138 requires the TPMS warning light to come ON when the tire pressure drops below 25% of the placard tire pressure. The TREAD Act/FMVSS 138 does not require the TPMS warning light to come ON when the tires are overinflated; however, there are systems available that do warn the driver of overinflation.

Does overinflation cause the same problems as underinflation of tires?
Overinflated tires can create a harsher ride on rough roads and when encountering bumps, cause a distortion in the tread and lead to increased wear in the center of the tread, reducing the contact area with the road. Increased wear due to overinflation will result in replacing your tires sooner than normally expected. Tires should always be properly inflated to the pressure indicated on the door placard and should never be inflated beyond the maximum pressure indicated on the sidewall of the tire.

Would I get a beneficial return on investment if I have TPMS installed in my pre-2007 car?
TPMS is an integral component of maintaining properly inflated tires. Vehicles with properly inflated tires will consume less fuel, have optimum handling characteristics, prolong the life of the tires and emit less CO2 compared with vehicles with underinflated tires. Fuel and maintenance savings help offset the cost of a TPMS Retrofit Kit for pre-2007 vehicles. Of course, the major benefit is ensuring the safety for the driver and passengers via TPMS.

If I get new tires on my post-2007 car, do I have to have TPMS put on them?
What will happen if I do not have it installed? The TREAD Act/FMVSS 138 mandate for implementation applies to the vehicle's manufacture date. It was phased into effect beginning in 2004. TPMS sensors are required in your vehicle if it was manufactured after September 2007 or if your vehicle was equipped with TPMS as original equipment.

If the TPMS light comes on, does that mean one or more of my tires are low?
When the TPMS warning light comes ON and stays ON, this indicates a low tire pressure condition in one or more tires. Some vehicles will alert the driver as to which tire pressure is low. Since one or more of the tires may be low in pressure, you should always check the pressure in all of your tires. When the TPMS warning light comes ON and flashes ON for one second and OFF for three seconds, this indicates a problem with the vehicle computer and can be corrected only by the dealership service center.

How often should I check my tire pressure?
A tire doesn't have to be damaged or punctured to lose air. All tires will lose air naturally over time, so it's recommended that you check the pressure in all your tires, including the spare, at least once per month. Road conditions, weather conditions or other circumstances may warrant checking the pressure more often. Remember to always use a quality tire gauge when checking tire pressure. And don't forget the spare! It may not have TPMS, but if you're checking your tire pressure, you should check your spare tire, too.

What does an underinflated tire look like?
You cannot always tell if a tire is underinflated simply by looking at it. You cannot easily tell if a tire is underinflated by kicking or pressing on the tire. The only way to accurately check tire pressure is by using a quality pressure gauge. A tire can lose air pressure without appearing to be underinflated. To see how little difference there is in appearance between a properly inflated and an underinflated tire, see the Interactive Tire Pressure Demo on NHTSA's safercar.gov Web site.

Where else can I go to learn about tire pressure and tire safety?
Go to our Helpful Links page, where you'll find a listing of online resources for further education and information about tire pressure and tire safety.

What is galvanic corrosion and why is it important (brass cap, core, extension or no cap at all)?
Galvanic corrosion occurs when dissimilar conducting materials, such as brass and aluminum, are in contact with each other electrically and exposed to an electrolyte. The galvanic corrosion reaction will cause one or more of the dissimilar materials to corrode. In the case of TPMS, if a brass valve core is installed into an aluminum stem or a brass cap is installed onto an aluminum stem, galvanic corrosion will occur and cause the two dissimilar metals to fuse to one another, resulting in damage to the stem, core and cap. Galvanic corrosion can damage the TPMS sensor beyond repair and will necessitate replacement of the sensor. Your tire service center will ensure that your TPMS system is properly serviced when you take your vehicle in for repair.

Additionally, a corroded valve stem, which also serves as the sensor transmitter's antenna, will affect the transmission of the TPMS data from the sensor to the ECU and may result in the TPMS light to illuminate.