Tire Sensor

Discussion in 'Prius v Main Forum' started by beachgeek, Nov 25, 2021.

  1. beachgeek

    beachgeek Junior Member

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    My 2013 Prius v low tire light comes on regularly. I filled the tires (very minimal air needed) and it went away - for a week. So I had the tire dealer check the tires. Tires have about 7,000 miles on them. No problem with the tires, valves, etc. That was two weeks ago and the light is on again. Yesterday the light was blinking after I started the vehicle, eventually settled down. Tires do not appear low.

    Do sensors go bad? Is that a fix that requires using Toyota? (Area dealers are notorious for unnecessary service.)
     
  2. Air_Boss

    Air_Boss Senior Member

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    TPMS wheel sensors are internal lithium battery powered and have a finite life, 5-8 years depending on use. When one approaches end of life, figure they are all near that cliff edge. Happy Thanksgiving.
     
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  3. jzchen

    jzchen Senior Member

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    The light, does it blink first? Then it is battery. After adjusting try pressing and holding the TPMS reset button under the driver dash (near your feet). It should blink to reset. Then you should be okay...

    Happy T day!!!

    REVVL V+ 5G ?
     
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  4. sam spade 2

    sam spade 2 Senior Member

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    Or to put it another way, the alarm threshold might be set too high so that it gives you an alarm when it should not.
    Getting the alarm set right should eliminate unnecessary warnings.
     
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  5. Mendel Leisk

    Mendel Leisk Sand Pounder

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    If you've got a pressure gauge and keep an eye on the pressures, you can just let it slide.
     
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  6. fuzzy1

    fuzzy1 Senior Member

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    The tires won't appear low until well after they actually need attention for low pressure.

    By "eventually settled down", do you mean the light went out, or did it stay on solid, no blinking?

    On, no blinking, means the car can't hear the sensor. This will usually mean the sensor's battery is dead or weak from cold, or the sensor has somehow failed, or disappeared (such as when I swap seasonal tires sets and forget to reprogram). Less usual, but something I have intermittently experienced, is that the car is temporarily not picking up a working sensor.

    If the light went out, then the car finally heard the sensor with a good pressure. This can happen if the pressure is slightly low and cold, but pressure increases slightly as the tire warms from use on the highway. When this happens, it usually means the pressure is too low anyway, add more. But it can also signal that the threshold warning levels are set too high (unlikely if you didn't intentionally 'recalibrate'), or that the gauge you are using to check pressure is itself reading wrong and causing you to underinflate. To verify, check with some additional gauges to see if they all agree.
     
  7. gromittoo

    gromittoo Active Member

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    I hope I have this right:

    1) Set all of your tires to the pressure you want to use as the "Trigger" for the low pressure light to come on. For example, I set mine to 26 lbs, which is well below the 35 lbs. front / 33 lbs. rear.

    2) find the stupid button under the dash near the steering wheel, and press it (Check the manual for how long you need to keep it pressed). Now your Low Pressure light is set for 26 lbs for all four wheels.

    3) Refill the tires to the proper 35/33 lbs., and the light should go out after a few minutes.​

    After doing this, you can believe what the tire setting says.

    BTW: a good excuse to get VCI? cable, and Techstream installed on a windows laptop. It is easy to see exactly what data the TPMS computer is using to set those lights. I believe that TPMS will also warn you if a tire is too hot.
     
  8. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Nope, you’ve got it “left”. I’ve been there…

    The warning apparently triggers when pressures drop maybe 25%. Accordingly, and presuming you’d rather have earlier warning:

    You want to set your pressures a bit on the high side, then do the TPMS reset procedure. Then drop the pressures to your preference. This’ll set the system to give you warning with less of a pressure drop.
     
    #8 Mendel Leisk, Nov 27, 2021
    Last edited: Nov 28, 2021
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  9. gromittoo

    gromittoo Active Member

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    Thanks for the correction. With Techstream, I can see what the limits are. I can see that all my tires are set at 25 lbs. I had to change a wheel, which meant changing the TPMS ID with Techstream.

    There is a free phone app called Tire Assist, which is supposed to do all of the TPMS management on most Recent Toyota models . It didn't work with my 2013 Prius v however. Something about the TPMS computer being on a different bus (K-Bus?), or my cheap ELM 327 adapter.

    The Tire Assist app is available for iPhone, but you need a Wifi based Elm 327 adapter.
     
    #9 gromittoo, Nov 28, 2021
    Last edited: Nov 28, 2021
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  10. beachgeek

    beachgeek Junior Member

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    No chance I am going to recalibrate, etc. The tires are not obviously low. I checked them myself but my fingers are creaky so I had a neighbor (younger) check. Then I took it to my tire dealer. I need to make a 300 mile each way trip (assuming we don't get shut down) and I wonder if I should worry. Tire dealer says no but he's not the person who could be stuck somewhere. I'm going in for an oil change at the dealer under warranty and I'm trying to learn what to believe and what not to believe when they tell me things. (They try to tell me I needed new tires about a month after I got new tires so I don't trust them.)
     
  11. beachgeek

    beachgeek Junior Member

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    Interesting. This is the first time I have ever seen it blink in the 6 years I've owned the car.
     
  12. sam spade 2

    sam spade 2 Senior Member

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    WHY not ?
    It is really simple.
    Just be sure the tires are at the proper pressure and the push the button.
    Done.
    You will be happy that you did.
     
  13. beachgeek

    beachgeek Junior Member

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    Do I want a new battery or can I just ignore this? I don't normally go far. I do look at the tires regularly. I am familiar with the "pull" of a low tire. I've never had a tire sensor befor.
     
  14. beachgeek

    beachgeek Junior Member

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    Ok, so I can let the tire dealer inflate the tires properly (I trust them) and then get back in the car and push a button? You are correct, nothing to lose. I'll try it. Thanks.
     
  15. sam spade 2

    sam spade 2 Senior Member

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    No, NO. BAD idea. Trust no one.
    Their idea of "properly" might be the 45 PSI it says on the side of the tire.
    Check them yourself......on insist on seeing it when they put the gauge on them.
     
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  16. Air_Boss

    Air_Boss Senior Member

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    Do a walk-around inspection, and if in doubt, check your tire pressures by hand.

    If you go the TPMS battery replacement route, which in many cases requires dismounting the tire, may as well replace the entire sensor.
     
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  17. fuzzy1

    fuzzy1 Senior Member

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    The coin cell batteries are sealed inside the sensors, not replaceable, so the entire sensors must be replaced. You can choose to ignore it if your state doesn't have regular inspections that require the warning light to be turned off.
    While you can still use the old look and feel method, TPMS will give earlier warning than you'll ever detect that way.

    One of my warnings was for a rapid leak caused by a puncture from a plumbing pipe hangar. The TPMS alert came earlier than I could feel it, prompting me to take the next freeway exit to a safe pullover place. Without that alert, I wouldn't have felt the low tire in time to take that exit, so would headed for the one beyond. But it was leaking fast enough that it couldn't have reached the next exit without rolling on the rim. That busy highway segment has a very narrow shoulder, making it a particularly unsafe place to deal with breakdowns.
     
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  18. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Here's an excerpt from the Owner's Manual, showing the procedure. I was gonna preach that all this stuff is in the Owner's Manual, but it took me about 10 minutes searching, in the (searchable) pdf version, to find this, ugh...

    I never know what quite what to do with this:

    upload_2021-11-30_13-43-30.png

    Think I did this once, and waited a solid 10 minutes, to be sure. Would be nice if they could be more specific. Do be cognizant: sitting with the car in "ON mode", is tough on the 12 volt battery. Do leave the vent system, radio etcetera off for this procedure. And maybe just do 5 minutes.
     

    Attached Files:

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  19. beachgeek

    beachgeek Junior Member

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    Thanks everyone. For me, removing the (buried in the wheel) cap on the valve is growing more difficult - the reason this issue is more of a problem. One person says leave them off since I don't drive a lot. Another says no way. I did see a valve extender (solving the buried issue) that doesn't have a cap that looks useful but some said yes and some said no.

    I don't think auto manuals are written for mere mortals. :(
     
  20. Mendel Leisk

    Mendel Leisk Sand Pounder

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    If yours has wheel covers, with them off I think it's a walk in the park accessing the valve caps. Going that route you want to get the centre caps though, to keep it pretty, and prevent hub rust (though I guess you're not in the salt belt).
     
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