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Glad to see this thread is not dead - TPMS is, IMHO, one of the dumbest things ever foisted upon people. First, people don't check their tires any more, which means they don't know what is happening. Second, these things are prone to failure at around 100K and are VERY expensive to replace (around $150-$200 on Subaru/Nissan/etc - I know, I've done both via company and 3rd party sales). They are incredibly inaccurate in the winter. Yes, tire pressure will drop - but the sensor should not trigger at 3% of the value. And they do. So now everyone drives around with their tires hyper-inflated, which makes them prone to skids. But, the reason I'm posting here is that the 2008 Subaru TPMS is useless. Even 2 dealers have had to admit they don't know why it comes on in my Impreza when it goes below 40 degrees (tires as high as 40 psi - reliably - by dealer measure). The dealers (3 so far) don't know how to turn it off. They don't know what's wrong since it sets NO code. And they don't know how to fix it. So we drive around for 6 months of the year with the light on. Been driving for over 40 years and have never been unable to maintain tire pressure adequately. It's another attempt to fix society with technology, and it never works. [I've seen the future, and it's still broken]. Yes, there was a problem with Ford Explorers, but now the rest of us are paying an incredibly high price for something of questionable benefit.
 

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2015 Forester, false TPMs since I bought it new, totally random. Dealer is Hunter Subaru in Hendersonville, NC and they cannot fix it. Drove a Ford Escape SE yesterday and I'm going to take a gas mileage hit, but other than that it looks like I'll go that way. Escape even has a little coverage for the pine needle trap over the lift gate. Been in Subaru since about 95, and the 2015 Forester 2.5i is the cheapest build I've seen. There could not be a better dust/debris trap of a car that has to live outside.
 

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Please explain how a safety feature that alerts the driver of a possible tire failure a "Scam"?
Calm down turbo. Tire Pressure Monitoring Systems are faulty and require a majority of consumers to spend money going into some kind of dealership store or shop to figure it out. A good percentage of MVAs are caused by faulty vehicles/poor maintenance so it makes sense to have the sensor system, however, it should also work appropriately and not require a professional's help so frequently due to operating abhorrently.
 

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Tire pressure is checked COLD and is even printed on the tire the recommended pressure cold. As you drive the air inside the tire heats up and expands increasing the pressure. The tire is designed to withstand the increase in pressure from heat. You may have one or two tires heat up faster and the pressure difference will turn the light on. When the other tires' temps catch up, the light goes out. Depending on the year model, the light will come on when the pressure drops below a specified measure, or it will come on when there is a pressure difference of 3-5% between tires. 3 tires at 35 and one at 31 will light the warning.

The Subaru TPMS will tell you what the fault is and identify which tire. You have to have a scan tool that will read the TPMS just like you have to have a scan tool to read other modules. A generic scanner will not always read modules other than the ECM. The manufacturers of the generic tools are not going to spend the money to provide this at a low cost. Scan tools that can read multiple modules and see live data will run $600 and up; as high as $7000 (but that $7000 tool from Snap On is not all it's worked up to be; my Autel MaxiDas does more for thousands less).

If you have a TPMS light and you check all the tires and the pressure is at or above the posted pressure on the door sticker, then you need to check your car's battery and cabling. Just like with other systems, a weak battery or conductance effects communication.

Other items in the car may also disrupt the radio communication between the tires and TPMS module. That phone charger that you got for $3, phones, iPads, aftermarket stereos, etc.
 

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Tire pressure is checked COLD and is even printed on the tire the recommended pressure cold. As you drive the air inside the tire heats up and expands increasing the pressure. The tire is designed to withstand the increase in pressure from heat. You may have one or two tires heat up faster and the pressure difference will turn the light on. When the other tires' temps catch up, the light goes out. Depending on the year model, the light will come on when the pressure drops below a specified measure, or it will come on when there is a pressure difference of 3-5% between tires. 3 tires at 35 and one at 31 will light the warning.

The Subaru TPMS will tell you what the fault is and identify which tire. You have to have a scan tool that will read the TPMS just like you have to have a scan tool to read other modules. A generic scanner will not always read modules other than the ECM. The manufacturers of the generic tools are not going to spend the money to provide this at a low cost. Scan tools that can read multiple modules and see live data will run $600 and up; as high as $7000 (but that $7000 tool from Snap On is not all it's worked up to be; my Autel MaxiDas does more for thousands less).

If you have a TPMS light and you check all the tires and the pressure is at or above the posted pressure on the door sticker, then you need to check your car's battery and cabling. Just like with other systems, a weak battery or conductance effects communication.

Other items in the car may also disrupt the radio communication between the tires and TPMS module. That phone charger that you got for $3, phones, iPads, aftermarket stereos, etc.
we have a 2015 outback, 94000 miles on it. Just yesterday, coming down from higher elevation, the tpms came on. First it was blinking, then stayed on solid. After a while, it went away. But soon, it came back on. Checked tire pressure, all 4 tires had the same pressure. Drove home. But this morning, the light is back on - blinking first, then solid. Needs an oils change anyway and I’ll talk to the shop (les schwab).

But reading your post made me reply. For the first time, we plugged in my wife’s brand new iPhone 12 to charge on the way down from the mountain. Any thoughts? Although, in the 6 years that we had owned this car, the tpms came on 3 times - I would be backing out from parking - each time there was a lot of snow. But once driving forward, the light would go away. Last time happened a couple of weeks ago.
 

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when the batteries in the TPMSensors get weak, after about 5 years, and when it is freezing cold out, they begin to have low voltage problems that make the light give false alerts.

In the summer, when it is hot, the errors go away, in the cold they come back..

driving heats up the tires, that also makes the cold old sensor battery start working better

I put electrical tape over my TPMS light on the dash, years ago. The sensors are cheap, but getting a shop to install them is expensive. Last year I bought new tires, and was going to buy new sensors. The shop tested mine and said I did not need new sensors. It was 85F outside that day. As soon as I got back into snow country, the light came on again. Not worth the aggravation to maintain the system, for me. I just ignore the TPMS, and walk around my car checking the tires, every time I gas up.
 

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@Thomas Dekany

Any phone charger can alter the communication circuits. The TPMS sensors send a radio signal and a receiver on the car, TPMS module, then communicates with the instrument cluster through the CAN network. The tire pressures are monitored when speed is over 25 mph. If the light is on when you park, it will check the system after the car obtains and holds 25 or higher and continue to monitor it while it's moving.

My 05 had to have new sensors put in at 135k miles.
Discount Tire will check your tire pressure monitors for free. At least they do here.

506097
 

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This is an old thread so I hope someone reads and replies to this. I have an 09 Outback,2.4L basic trim model. It has 115,000 miles. Recently the TPMS light began to blink on the highway for about 15 miles, then went off. Air temperature was in 70's.m Then when on highway again in 80's weather it came on and has stayed in the mode of blinking upon starting for about 2 minutes, then goes to solid and remains lit for the duration of the drive. Tire pressures have been checked and set at 32 (all 4) with a new guage and an old compressor at home. Same light pattern. My battery develops heavy white corrosion at the hot terminal pretty readily. At the same time of this TPMS issue I removed the battery, and the tray and cleaned all parts and reconnected. No change in sensor light. Coincidentally, about the time the light became an issue the rear hatch lock failed on the key module. The four doors would lock, not the hatch. This was discovered when the hatch was opened and the alarm went off. Is there a sensor connection between TPMS and door lock system? Is it just the hatch that is in line with the TPMS? Help. Thanks
 

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@Mariposawrick
A flashing TPMS light means there's a fault. A good repair shop should be able to scan the car's modules/computers and see what faults are there. Given your mileage and the age of the car it may be a bad pressure sensor on one or more wheels.

As I posted in the post just prior to yours, Discount Tire will check the TPMS sensor signals for free, at least they do here. If you need a sensor they will install the sensors for a price that you can get from Subaru. The ones here can't seem to program the sensors though, so it may be just as well to visit the dealer for the install and programming. But you first have to verify whether the sensors are working or not.

On the battery, if there is build up on the positive post really quick after cleaning it, then that indicates the seal between the post and the plastic case is bad and acid is leaking out, which usually means the battery output sucks. Also, the grounding from the battery to the engine needs to be good, as well as the body ground that goes to the driver fender behind the fuse box. Bad grounds cause communication problems and the computer may not be getting the signal correctly from the wheels due to bad grounds.
 

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Tire pressure is checked COLD and is even printed on the tire the recommended pressure cold. As you drive the air inside the tire heats up and expands increasing the pressure. The tire is designed to withstand the increase in pressure from heat. You may have one or two tires heat up faster and the pressure difference will turn the light on. When the other tires' temps catch up, the light goes out. Depending on the year model, the light will come on when the pressure drops below a specified measure, or it will come on when there is a pressure difference of 3-5% between tires. 3 tires at 35 and one at 31 will light the warning.

The Subaru TPMS will tell you what the fault is and identify which tire. You have to have a scan tool that will read the TPMS just like you have to have a scan tool to read other modules. A generic scanner will not always read modules other than the ECM. The manufacturers of the generic tools are not going to spend the money to provide this at a low cost. Scan tools that can read multiple modules and see live data will run $600 and up; as high as $7000 (but that $7000 tool from Snap On is not all it's worked up to be; my Autel MaxiDas does more for thousands less).

If you have a TPMS light and you check all the tires and the pressure is at or above the posted pressure on the door sticker, then you need to check your car's battery and cabling. Just like with other systems, a weak battery or conductance effects communication.

Other items in the car may also disrupt the radio communication between the tires and TPMS module. That phone charger that you got for $3, phones, iPads, aftermarket stereos, etc.

While driving to the store earlier today my TPMS light came on and stayed on solid on my 2013 Outback that I bought a few weeks ago, and will not go off despite all my tires being (and staying) inflated to the proper pressure. I don't have anything in the car other than my phone and a USB drive plugged in- could one of these be causing the issue? Would a bad sensor cause a flashing dash light or a solid light?
Is this a dealer-only service to fix this issue? Or can take it to Wally World or some such?
 

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While driving to the store earlier today my TPMS light came on and stayed on solid on my 2013 Outback that I bought a few weeks ago, and will not go off despite all my tires being (and staying) inflated to the proper pressure. I don't have anything in the car other than my phone and a USB drive plugged in- could one of these be causing the issue? Would a bad sensor cause a flashing dash light or a solid light?
Is this a dealer-only service to fix this issue? Or can take it to Wally World or some such?
Check Discount Tire. They have sensors that work on your Gen car and may be able to program them. Otherwise, dealer or call around to different tire stores in your area.
 

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Tpms transmitter batteries are good for 7-8 years or so. If you have issues on sensors that old they are due for replacement. The batteries are potted in epoxy and can't be serviced.
 

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After doing a bit more research on this, I discovered the TPMS sensors are mounted to the inside of the rim (i.e. you have to take the tires off to get to them.) SO a bit more info might be warranted here:

Last Saturday I took all 4 wheels off the car and took them to a local tire shop to have the tires swapped on them. I reinstalled the wheels on the car, and then the next time I drove it was when the TPMS light came on on the way to the store. But now I recall that a couple minutes before that happened, as I was driving down the first street I turn onto out of my neighborhood, I heard what sounded like something metal suddenly kicking around loudly inside a wheel for a second or two (as if one of the wheel balance weights had come loose, kicked around the spinning wheel and then shot out of the wheel.) I thought maybe I had just kicked up something on the road but now I'm wondering if a TPMS sensor could have come loose, and if so could this have been caused by the tire swapping? And, since they are on the inside of the rim, is there any way it could have actually exited the wheel since I only heard the sound for a second or two?
 

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A piece of black electrical tape over that yellow light on the dash has worked for me for over 5 years now. A few day's after having new tires mounted, the light came on, the Tire Shop told me two sensors had dead batteries. They are still there, dead, the car drives fine. Black tape is your best, cheapest route. Not only that, but my winter wheels, OEM (Spec B wheels) have different sensors, so if I want the light to go out with them on, I have to go to a tire shop...again, the black tape works great.
 

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After doing a bit more research on this, I discovered the TPMS sensors are mounted to the inside of the rim (i.e. you have to take the tires off to get to them.) SO a bit more info might be warranted here:

Last Saturday I took all 4 wheels off the car and took them to a local tire shop to have the tires swapped on them. I reinstalled the wheels on the car, and then the next time I drove it was when the TPMS light came on on the way to the store. But now I recall that a couple minutes before that happened, as I was driving down the first street I turn onto out of my neighborhood, I heard what sounded like something metal suddenly kicking around loudly inside a wheel for a second or two (as if one of the wheel balance weights had come loose, kicked around the spinning wheel and then shot out of the wheel.) I thought maybe I had just kicked up something on the road but now I'm wondering if a TPMS sensor could have come loose, and if so could this have been caused by the tire swapping? And, since they are on the inside of the rim, is there any way it could have actually exited the wheel since I only heard the sound for a second or two?
If those are the original sensors that came on your 2013 when new, then they are around 10 years old and at end of life. So it could be coincidence that they came on now after tire replacement.

But let's look at your bill. Were you charged for valve stems or possibly listed as "TPMS Service Pack"? If so, then the tire store replaced the valve stems (which they should have!), and may not have properly screwed the sensors to the stems. One might have come loose and is banging around inside the tire. No, it could not have exited, but it could have been damaged. If so, the shop should accept responsibility if they were negligent in their actions.

I recently had a sensor damaged when I had a slow leak repaired. The shop acted like it was no big deal, and that they weren't responsible! But indeed they are! There are procedures to be followed when removing/replacing tires to avoid whacking them, and procedures for proper removal and reinstallation of the Schrader valve stem and reattachment of the TPMS sensor. The store owner admonished his employee, and replaced the sensor. But I had to reprogram (re-register the sensor to the Forester) when I got home.
 
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If those are the original sensors that came on your 2013 when new, then they are around 10 years old and at end of life. So it could be coincidence that they came on now after tire replacement.

But let's look at your bill. Were you charged for valve stems or possibly listed as "TPMS Service Pack"? If so, then the tire store replaced the valve stems (which they should have!), and may not have properly screwed the sensors to the stems. One might have come loose and is banging around inside the tire. No, it could not have exited, but it could have been damaged. If so, the shop should accept responsibility if they were negligent in their actions.

I recently had a sensor damaged when I had a slow leak repaired. The shop acted like it was no big deal, and that they weren't responsible! But indeed they are! There are procedures to be followed when removing/replacing tires to avoid whacking them, and procedures for proper removal and reinstallation of the Schrader valve stem and reattachment of the TPMS sensor. The store owner admonished his employee, and replaced the sensor. But I had to reprogram (re-register the sensor to the Forester) when I got home.
Gotcha- thanks for that info!
Yes they did indeed replace the valve stems, I did not realize that the TPMS sensors attach to the other side. Being a recent purchase I had only driven the car a few times before having this done, but the TPMS dash light was never an issue until after they replaced the tires.
I'll call them back and ask about it- I also think one of the tires they installed has a slow leak on it as well so I need to take it back to them anyway.
 

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@subiedummie
It will cost you less to replace them all in one visit. And check the slow leak.
Mention a suspicion of corrosion on the rim bead surface...
 
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