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Discussion Starter #1
I have been a Jeep girl for 10 years, and I am completely new to Subarus and TPMS, so please pardon my inexperience. Anyway, I just picked up a 2005 OB sedan 3.0R, and the TPMS flashed after a few miles of driving. I have the tires inflated to the proper psi, so I don't know what else it could be. I am still under the dealer's 3 month/3k mile drivetrain warranty, and want to get them to fix it before I try fiddling with it myself. What could it be, and if they "fix" it, is their a way to check that they didn't just disable it? If it matters, there is 71,500mi on the clock.
 

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I would have them check the battery life of the TPMS. The ones on your car are reaching their life expectancy.
 

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Battery for the TPMS tire sensors is a very real possibility. They won't disable it, that would be illegal. At 71k if you still have the original tires it should be time for new ones. If you have fairly new tires someone cheaped out on you.

In order to fix the battery you have to re-mount and balance the tires.

Of course it could always be the sensor in the car or the environment. TPMS works via radio waves and there can be local interference sometimes. If it only happens in the same place everyday for example.

If it were me I would ignore it until I needed new tires, but then I have to get tires often.
 

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When the TPMS light flashes, it's indicating a problem in the TPMS system, not a low pressure. (Low pressure in a tire is indicated by the light coming on steadily.)

Each wheel has a pressure sensor. The sensor has a small radio transmitter that sends a signal to the TPMS control module. These signals are coded with a unique number for each sensor, and each of the four numbers is stored (registered in) by the module. Only four wheel sensors can be registered at any one time. This way, the module knows which wheel sensor is which, and will not pick up signals from a sensor that has not been registered (so that it won't pick up a low pressure signal from a Subaru parked next to your car!).

The TPMS sensors automatically turn off when the wheels are stopped for some time (e.g. parked), and then turn on again after the car has been driven for a while. The control module will expect to receive signals from each of the four wheels after the car has resumed movement which could explain why the light starts flashing only after 7+ miles.

A situation that could lead to the flashing TPMS light is when the wheels are replaced, and the TPMS wheel sensors that are registered in the control module aren't transferred to the new wheels. Another might be a damaged wheel sensor, which can happen when tires are being replaced. And then, although the batteries in the wheel sensors are supposed to be good for at least 10 years, it's possible one or more could be weak.

If the car was bought from a Subaru dealer, they can determine the reason for the flashing by connecting the Subaru Select Monitor to the car and monitoring the TPMS control system. (Might have to take the car out until the light flashes to read the code.) If there is flashing, a code will be stored in the module's memory, and that code will indicate the nature of the problem.
 

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Discussion Starter #5
Does the tire need to be removed to replace the TPMS? I am going to bet that the dealer I got this from isn't going to do this under warranty as it is a "wear item," but does Subaru or a mechanic need to do it, or can it be done by a lay person with tools?

Also, I have an OBD II scanner thingy <--- technical term, will this read those codes, or is a special scanner needed?
 

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A special scanner is needed to read the TPMS codes. There's a possibility some tire shops, or independent mechanic might have equipment that can do it, but I suspect that would be rare. However, some shops might be able to detect whether or not each of the sensors is working by using a different type of scanner that is specifically for TPMS systems.

To access the sensor/transmitter in each wheel, the tire has to come off.

First, you can check to see if your wheels appear to be equipped with the TPMS pressure sensors. Attached is a diagram of the sensor. The sensor is fitted inside the wheel in place of the normal fitting where you inflate the tire. The TPMS fitting typically has a nut whereas the more common type of inflation fitting is all rubber. (There could be variations, but if the fitting is just a normal, rubber type, it's more likely the TPMS sensors aren't installed.)
 

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Discussion Starter #7
Thanks, guys, I appreciate the feedback. I just called the the dealer I purchased the car from about this issue and the vibration/torn cv boot (another thread), and I am waiting on a call back to hear what the have to say as far a fixing them under the warranty.
 

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Please let us know how it turns out.
 

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This is a late reply, but if your tire pressures are good and holding steady then try adding a couple PSI over the recommended amount and see if the TPMS light goes away. My light would come on after driving for 30 mins or more. I talked to one dealership and they recommended 35 PSI all around. My car ended up at another dealership for engine work and THEY noticed the TPMS had come on and told me about it. They aired the tires up to 35 PSI and recommended to me to keep them inflated at that pressure. I will say that both dealership also stated it was due to the higher elevation that we have in Colorado, but it couldn't hurt to try.
 

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This has not happened to my Subaru but has happened to my Nissan Titan - almost exactly as you described. Flashing after a few miles but with no sound. Note that when there is an actual low tire pressure, the TPMS in the Titan also sounds off (buzzes) in addition to a steady light.

I checked all of the tire pressures and they were all at or above what was required. What I did not check was that the tire pressures were equal. The Titan has all four tires at the same pressure. The Subaru has different front and back pressures. I equalized the tire pressures in the Titan and the problem resolved. Good luck.
 

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For me, my tpms flashes after exactly 21 minutes, Thanks to the in-car timer which tells me how long I've been driving. I'm also wondering a fix for this. I plan on having the tires replaced in the next 6 months, but it would be good to know if it's just one of them or if it's something else.
 

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This is a late reply, but if your tire pressures are good and holding steady then try adding a couple PSI over the recommended amount and see if the TPMS light goes away. My light would come on after driving for 30 mins or more. I talked to one dealership and they recommended 35 PSI all around. My car ended up at another dealership for engine work and THEY noticed the TPMS had come on and told me about it. They aired the tires up to 35 PSI and recommended to me to keep them inflated at that pressure. I will say that both dealership also stated it was due to the higher elevation that we have in Colorado, but it couldn't hurt to try.
This is an even later reply, but the OP's TPMS light is not coming on, it's flashing which as others have stated and Pep Boys have told me today indicates a problem in the system, not a low pressure. I am having the same problem right now (flashing) after having new tires installed and have had to go back to Pep Boys twice already. They say that all 4 transmitters are OK and reset the TPMS again. After reading the comments above about 9-21 miles and the flashing starts again, I am less than optimistic they have fixed the problem. The shop is only about 4 miles away. I suspect they have damaged a sensor because when they first serviced the car they asked me if it has TPMS and I told them I didn't know. The service manager confidently said no, it didn't, and that only 2007 or later cars have it. To be continued.
 

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Ryank25, was your issue ever resolved? I'm having the exact issue on my 07 OB. The light flashes when first started, I assume everything is OK in the system. Driving for 21-22 minutes and the light will begin to flash once ever 3 seconds. Shut the car off, restart, light flashes for normal system operation, then is fine for another 21-22 minutes where the process repeats.

-John
 

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I would check the harness connection at the TPM unit under the seat to make sure it's dry and not corroded. It it passes, have the TPM codes read.
 

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When the TPMS light flashes, it's indicating a problem in the TPMS system, not a low pressure. (Low pressure in a tire is indicated by the light coming on steadily.) ...
thanks for the info, will get it looked at
Video link, recently my TPMS flashed going over mild road bumps, one time only so far.. Tires were not underinflated.
 
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