Home 2011 Editions April, 2011

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It’s time to charge up tire dealers’ customer education campaigns for TPMS sensor replacement as the life expectancies of batteries molded into sensors begin to run out.
When asked how long TPMS sensor batteries will last, industry representatives provide a broad life expectancy range - five to 12 years and up to 100,000 miles.
Mandated TPMS systems were phased in from 2006 to 2008, so some of these vehicles’ sensors have been in service for five years. Still older direct sensors can be found in quite a few domestic and import models introduced earlier in the decade and equipped with TPMS ahead of government deadlines.

Direct TPMS sensors commonly use radio frequency technology to transmit measured tire pressure readings to a vehicle’s on-board electronic control unit and warn drivers of a 25% or more under-inflation level.

Mounted inside a tire assembly on valve stems or wheel rims, the sensors are usually powered by 3-volt lithium ion batteries, but some use 1.25-volt nickel metal hydride batteries. There are developments underway that promise battery-less sensors in the future, having the potential to dramatically change TPMS markets.

For now, though, the batteries – generally round and encased in a sensor’s molded plastic housing – have finite lives. Since the batteries are entomb­ed, a dead or dying one requires the replacement of its entire sensor assembly.

When asked how long the sensor batteries will last, industry representatives provide a broad life expectancy range – five to 12 years and up to 100,000 miles are mentioned when addressing estimated life spans. The follow-up qualifier is that driving conditions, such as frequent on-off cycling of a TPMS, tire pressure sampling frequency and temperature extremes, will significantly shorten battery life.

When Batteries Die
A failed battery means its sensor no longer is providing protection to the vehicle driver and passengers, just like an inoperable home smoke detector can’t warn occupants of a developing hazardous fire.

A smoke detector’s single, short beep at long intervals alerts a home­owner to change a battery, but how does a car or truck’s on-board computer know that a TPMS sensor’s battery has failed?

Brian Rigney, general manager for Dill Air Controls Products, conducted an experiment to determine how one vehicle reacts to a sensor’s lost transmission.

“A car’s computer recognizes that a signal interruption has occurred, Rigney says, “but it usually waits to react.”

Automotive makes and models have many different systems, he says. Generally, sensors are design­ed to transmit data to the computer at regular intervals, usually measured in minutes. If the computer misses a few sensor transmissions, it assumes interference has occur­red and refrains from alarming the driver. However, if the computer misses several more transmissions, it illuminates the TPMS icon to alert the driver of the malfunction.

Rigney tested a Pontiac model by completely removing a sensor from a tire assembly and driving the car. “It took 45 minutes before the TPMS icon warned me the computer was not receiving a sensor signal,” he says.

“My test vehicle’s system was set up for the 45-minute delay, but other cars are programmed for longer or shorter time periods.”

Real Life
It was time to ask for his battery life estimate.

“Each manufacturer has its own warranty, some are simply two years, some are years or miles,” Rigney explains. “An OE sensor battery is expected to last at least five years, which is usually outside the warranty time period.”

He says battery life expectancy is directly related to the number of RF transmissions, which are affected by driving conditions and the sensor design. “Does the sensor have a sleep mode? Is it designed to transmit every minute, five minutes or 20 minutes in normal conditions? Gen­erally, an OE battery will last five to 12 years and the average is seven years.”

Colder conditions generally allow batteries to last longer, according to Rigney, so batteries are expected to fail quicker in warmer rather than colder climates given the same driving conditions. However, driving habits vary greatly from tire customer to customer, and by the same token, the demand placed on sensors and batteries also fluctuates widely.

Sensors usually transmit less while a vehicle is stopped, more often while it’s in motion, and a lot more as it accelerates or decelerates. A constant speed, such as highway driving, allows sensors to transmit less often.

In general, short distances with numerous starts and stops will have a greater impact than overall miles driven. “In other words,” says Rigney, “10,000 city miles will result in lower battery life compared to 10,000 highway miles.”

Battery Replacement
A depleted battery can’t be ex­changed, so the entire sensor must be replaced.

Rigney says potting material inside the sensor housing secures the electronic components and protects them from the harsh environment inside a tire. “In order to remove a battery, the potting material would need to be melted. Heating the material could damage components and allow the battery’s lithium to seep out of its housing and into the environment.”

A NHTSA ruling, says Rigney, stated that TPMS and its 71 million tiny batteries represent a 2% increase in U.S. battery usage, but a much smaller overall increase in battery volume and chemical content to landfills. Balance that against the environmental benefits of TPMS-improved proper tire inflation rates that include improved fuel economy, reduced emissions and longer tire life.

When a customer visits a tire dealer, a technician can test each TPMS sensor’s battery life, but only if his or her scan tool can display battery life and the pressure sensor is equipped to output that data. Rigney cautions that it’s difficult to interpret the scanned data, because the readout could be a battery life percentage or a one-word description. “A displayed ‘10 %’ or ‘low’ could mean six mon­ths to a year of battery life remaining,” he says.

The lack of accurate information opens the door for a conversation to discover a customer’s expectations and explain the needs.

Rigney believes the TPMS and tire service industry should adopt standards. “Standardize sensors so they output battery life information and standardize scan tools so they display battery life,” he says.

He adds that the industry also should agree that a “low” or “15%” readout is the proper time to recommend to customers that they replace all four tire sensors and recheck the spare if it is TPMS-equipped. “It’s similar to replacing both headlights at the same time, even though only one is burned out.”

He adds that if a vehicle owner is buying new tires and one sensor battery is dead or low, the technician should explain it’s the best time to replace the sensors because:

• The tires already are off the wheels, so buying now means avoiding a future visit to the dealer and additional charges for a second balancing service.
• It could avoid the TPMS warning light appearing while on a trip or in traffic.
• It would eliminate the worry of dealing with a failed sensor.
• Replacement sensors, such as those made by Dill, can last seven to 12 years, which normally means never purchasing another set of sensors. So buy them now, instead of later.
• Some states require TPMS icons to be off in order to pass vehicle inspections.
• Replacing all sensors, before or when one fails, helps avoid a last-minute issue while preparing for inspection.

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  • Art macson

    Someone needs to come out with the replaceable battery in the tire pressure monitoring system when you have to pay $60 for one plus labor I think that’s out rages times four$$$$$$$$$$$$. I have taken one on the tire pressure monitoring modules apart and found out that the battery was made in China

  • DeadReckoning

    Why can’t they use some of the rotational forces in the wheel to charge up a capacitor in the sensor – a bit like the way a (battery less) casio kinetic watch works?

    • fairy

      Cost and reliability. Probably would wear out in the same time the battery dies in a normal TPMS.

      • Nick A

        I partially agree. They will most likely cheap out on the capacitor, and put a size that is “just barely enough to handle”. They may also throw out some BS about a capacitor exlosion, which wouldnt be much different than a battery explosion, and completely avoidable by using a larger capacitor. And from what I can tell, a capacitor that never reaches near max charge, will outlast any battery on the market.

  • LoneRanger

    That would be too easy.

  • Jeff

    These stupid devices remind me of what we use to call idiot lights that would come on when your out of oil,water, brake fluid,are Americans really getting that stupid,or are these kind of devices just made to make some stupid people rich. How can I deactivate this monitor system ,I am old school I check my tires and fluids.

    • Villi age

      Yes to both,relying on some gadget to do their thinking.Being lazy is also a factor.

      Some people are “all thumbs”…just watch them text!!!

  • SapientHetero

    The sensors on my 8-year-old car with 48,000 miles on it have failed. Dealer wants $800 to replace, first tire shop I called wants $700. With all due respect to the author of this article (in my case, not much respect at all), how exactly is it a good deal to pay this much to turn off a warning light versus periodically checking tire pressure like a responsible car owner? Thanks to overzealous Washington morons, motorists are wasting millions of dollars a year on this crap. One more reason to strangle the bureaucracy by cutting off its money.

    • Noname

      Exactly. I have 2 sensors out on a 6 year old car. Just had new tires installed one year ago. Took into shop to have tires rotated yesterday. It would cost $180 plus tax to have the two bad sensors replaced. i told them I could just check the tire pressure myself for that kind of $$. What a waste of time, dollars and effort rolling out the entire TPMS bullsh*t. If any person cannot check their tire pressure, they shouldn’t have a license any longer. It’s so easy my 5 year old can do it.

      • RoadCrimeUK

        The point is the TPMS is not to replace regular manual checking, but to monitor the pressure while driving giving advance warning of pressure lose, warning of a problem before you feel a problem. More time to choose a place to pull over.

        • brownj00

          Except… it can take 15, 30, or 45 minutes to alert or report a low pressure result depending on the car and settings.
          That kind of defeats the theory this is going to give you advance warning so you have more time to pull over. That’s hardly a useful timeframe for emergency avoidance.

          • RoadCrimeUK

            Total rubbish, loss of pressure due to a puncher is indicated immediately, the timed transmissions relate to normal operating conditions.

          • brownj00

            The catastrophic loss of pressure, you mean? That was not what he said. It sounded like he was talking about “normal operating conditions”… not a sudden emergency (where you would feel the problem immediately).
            My understanding is the car has to “ask” the sensor for the current value – and most cars do that every 10-20 minutes depending on their programming. Frequent checking is also going to run down the battery.

    • Eric

      Try ebay, you should be able to get them for $25-35 a piece, and have them replaced next time when the tires get replaced.

      • Joe Canuck

        $8 each, free shipping, you just need to be able to replace a valve stem youself

        • SapientHetero

          Not for ones my Lexus recognizes.

        • Harry Wookiee

          Until the embedded battery dies.

    • Moss Miller

      In your case, for $800 you could just about get a set of new alloy wheels, tires and TPMS sensors including road force balancing from Tire Rack; although to turn off the light you would might need a reset tool (such as on most Japanese cars). Tire rack installers could receive the tires, install them and reset the codes on your on-board computer. For home users, the reset tools cost about $325, but I needed them as I switch to winter tires each fall and my Subaru can only hold codes for one set of 4 sensors at a time. Many American cars can now adjust to new sensors without a reset tool. And some cars, such as the Mazda 6 and Honda Accord, do not use sensors but rather the ABS system to determine if a tire is low.

      • SapientHetero

        Probably not. I have a 2007 Lexus GS350 with monstrous rims and high-grip tires. The tires alone cost $1,000 per set of 4.

        • brownj00

          Oh well, you can afford it then. Right? :D
          Yeah, I do know some sports cars have tires in the $400-500 range. Each. Sucks to be special, huh?

    • Bob Walen

      I just had one replaced on my 2010 Hyundai Accent SE at my local tire shop in Havre, Montana. Total cost $40.00 and yes it has alloy wheels.

  • Jim Triebwasser

    Skip, Thanks for the insight. My 2007 Frontier was not part of the Nissan recall for TPMS, although it should. I also agree with Jeff, that if you have a car, learn to take care of it. Check your fluids, tire pressure, water by using your eyes. As far as maintenance, get a stack of 3×5 cards, write out the intervals, and add any repairs to the back of the card. Wrap with a rubber band and toss it in the glove box.

  • eric

    TPMS sensors, and the failure that come with them, is another example of our “leaders” deciding on HOW that is done, rather than Should it be done. The concept of monitoring air pressure and keeping it correct does have merit, but the current, mandated process of requiring a sensor in every wheel is a poor design due to high failure and maintenance requirements. The same could be accomplished by measuring the wheel rpm (which is done today anyway) and monitoring a change in that as compared to others. This will allow a light to illuminate and warn the driver of an underpressure tire. The difference? Systems in the past only turned a light on, it didn’t tell you WHICH tire was low. Unfortunately, our elected officials thought we are too stupid to figure that out so the requirements forced each wheel to report separately. In other words, as often the case, cost and unnecessary maintenance was added to the price of the vehicle because a politician made design decisions for us. Sad.

  • steve j.

    I agree with the comments that the TPMS system is a total waste of money and demonstrates how bureaucratic intervention into our lives makes things worse, not better. I have a Ford Escape with a wheel sensor failure, and yes, the dash display does not tell me which sensor, so I have to either 1)buy a $250 tester to narrow it down, or 2) take it to a shop and let them charge me a boatload of money to troubleshoot and fix it. Of course, the Escape has dozens of other annoying sensors that do about the same thing, as referenced by others with the term “idiot lights”. My only questions is why Ford and other manufacturers go along with these stupid ideas? Oh yeah, because they make lots of money in their service departments…

  • j

    I can appreciate both sides of haters & lovers.

    For me, TPMS has saved me while driving. The low tire warning light turns on. I pull over quickly, and check w/ a digital air gauge , to see which tire is suspect. All these times it was due to an unseen nail/screw that let out air while driving. Sadly, every company car I have been isued (every 2-3yrs), has received a flat while driving. W/O TPMS, I would not have been able to pull over in time, b/c I would not felt/realized a tire was flat until too much air was lost. I have been on the premature replacement end on my older, personal car; again, due to a nail/screw letting air out while driving.

    I do check my tires regularly, while COLD. I even check the spare twice a year.

  • barry

    my 2013 Cadillac will indicate the pressure in each tire and show it’s location. the sensors are only $20 each. and I will replace them when I get my second set of tires. what the hell is the problem?

  • Miike Drrop

    yup another disaster of “bureaucratic unintended consequences” proportions, combined with poor engineering on the part of some or all manufactures.

    Great, so we now have a system to tell our tires MAY have low pressure, but on my particular car (08 Toyota) you can’t rotate tires position – as is wise and common and economical-, you can’t incorporate a full size spare in your rotation ( giving you a Real Tire to switch to an event of a blowout) , and you can’t even switch between summer and winter tires sets,

    without an expensive programming tool or slinking into a tire shop.

    It seems fairly likely that the increased expense these ridiculous systems exceeds the value.

    I can hardly wait to see the regional wide traffic jams self driving cars will contribute to our lives

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