what's latest on Low Tire Pressure Warning light issue?

Discussion in 'Gen 4 Prius Technical Discussion' started by The Big Sleaze, Sep 26, 2021.

  1. The Big Sleaze

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    There seem to be a hundred threads going back to at least 2007 models (mine is 2020 Prime base model 33,333 miles) but no solutions.

    Is it just something you live with as a minor defect you wouldn't have ever wanted in the first place?

    How does it even work? Is there sensor in the wheel with connection or wireless (battery?) or does it work by detecting the tire's ride being a bit too soft? Does it feel the other tires hit same bump and detect difference?
     
  2. sam spade 2

    sam spade 2 Senior Member

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    There is NO overall "defect" or "issue" with the TPMS.

    The detection happens at the base of the tire stem inside the tire......where there is a tiny transmitter and a battery.
    It detects that actual pressure.

    Like any other electronic system, they sometimes are damaged or fail prematurely.......or the batteries eventually go dead.

    Why do you ask ? Isn't your car still under warranty ??
     
  3. The Big Sleaze

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    thx, Sam. Its not just me and not just Toyota because I've had at least 3 older folks with "new fangled cars" ask me about TPMS and have me checking their tires, etc on other makes, and also that the TPMS seems to be the ONLY thing going haywire.

    Yeah, I guess I'm under Warranty but is PIA to visit dealer service dept and what is the remedy? Do they use the Dealer Only Black Box to figure out which tire it is and then do they got to R&R the tire to get to pull in a new Valve Stem from the inside of wheel? Because if so I rather not bother and not risk the idiots at the dealer hurting my tire in the R&R process. Is there a way to see which tire they are saying is low?

    Maybe I'll invent a TPMS that uses a sensor that sits on the tail of the valve stem core so it can be replaced without R&R the tire.

    PS-haven't been to dealer since I used up my two free oil changes at about 16,000 and I'm now at 33,000 doing own oil changes, so is there any other good reason to visit dealer prior to warranty expiring? Will I get free engine air filter or cabin filter, wiper blades etc?
     
  4. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Just to ask the stupid question: you've checked the tire pressures?

    On the off-chance your tpms system is set to too high a threshold, I'd suggest: with your usual pressures set, do the tpms sensor reset procedure, see if that helps. From Owner's Manual:

    upload_2021-9-26_13-16-49.png
     
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  5. The Big Sleaze

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    Yeah, they all seem about exactly 32psi, so I guess I'll try going to 36psi.

    Thx for the link to manual ("pg 734" yipes, its like a Russian epic novel, but not a "page turner").

    Any info on how SENSITIVE the TPMS is? It first came on then went off, now on full time but tires still reading about exactly 32psi same as last tire rotation from dealer at about 15,000 miles ago. Factory tires seem to be holding up nicely at 33,333 including a fair amount of 90+mph commuting.
     
  6. ChapmanF

    ChapmanF Senior Member

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    If you have access to Techstream you can just look; it will show what the low-pressure alert threshold is.

    It doesn't give you any direct way to set the alert threshold. The only way is to air your tires up to some pressure, then use the "this is the pressure I want" button under the dash, and it sets the alert threshold to a number below that.

    It picks a number pretty far below ... If I remember right, if you air up the tires to 35/33, say, and push the button, it will set alert thresholds in the 20s.

    That's too low for my taste, so what I did one time was I aired up the tires to about 44, the maximum rating on their sidewalls, and pushed the button then, and it set thresholds in the mid-30s. Then I let the tires back down to about 38/36 where I typically run them, and now I get a notice as soon as they start to get low, which is more to my personal taste.

    If one of them has a low battery or isn't transmitting, you'll see that in Techstream too.

    But it only shows you their ID numbers. It doesn't know which transmitter is at which corner of the car.

    I just figured that out one time, by letting air out one tire at a time and watching the readings in Techstream, and then airing them back up. Since then, I just update my map when I rotate the tires.

    That also gives you a way to confirm that somebody else really did rotate the tires, if you paid for it. A little stealthier than making chalk marks.
     
  7. fuzzy1

    fuzzy1 Senior Member

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    Every tire shop has the tools to directly read what the sensors are transmitting, so they can easily find what numbers are being transmitted, or find if a particular wheel's transmitter isn't working.

    If all pressures and sensors are good, then try the initialization procedure described at post #4.

    If the problem still persists, then go to a Toyota shop for possible system failure under warranty.
    No, those are not warranty items.
    What does the door label say? 32 sounds lower than recommended for the standard tire size.
     
  8. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Second that. As @ChapmanF said, might be 35/33 (F/R), but check against drivers door decal.
     
  9. bisco

    bisco cookie crumbler

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    air 'em up to around 40, you'll never see the light again
     
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  10. FuelMiser

    FuelMiser Senior Member

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    Raising tire pressure it NOT the answer (sorry "bisco"). Re-calibrating the TPMS following the instructions IS the answer.
     
  11. ChapmanF

    ChapmanF Senior Member

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    Or your fillings.
     
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  12. sam spade 2

    sam spade 2 Senior Member

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    I asked that too and got no answer.
    Another case of "My mind is made up, don't confuse me with facts."

    In addition to the safety aspect, the TPMS system kind of forces people to learn a bit about how tire pressure really works.
    That is NOT a bad thing.

    But he doesn't want to hear that.
     
  13. sam spade 2

    sam spade 2 Senior Member

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    OMG. THIS is why he thinks there is a problem HE doesn't understand how it works either.
    This is NOT the right thing to do.......but others have probably told him that already.
     
  14. vvillovv

    vvillovv Senior Member

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    I agree @FuelMiser that is the easy way, but @The Big Sleaze doesn't like reading boring stuff like @Mendel Leisk posted above. I do what @bisco recommended and air them up (but I still have the darn light on cause of my new sensor, double darn). @Mendel Leisk said "just put black tape over if it bugs you too much" @fuzzy1 If I remember correct like - for my 17 Prime Plus with 15 in the door jam says 36 front / 34 rear and I just re initialized at 40 all around last week. ;) And @ChapmanF I've already lost most of my newer amalgams and I don't think they can go any deeper in there than they already have. Most of the old ones are still hangin there - maybe that is lucky for me... who only knows for sure, Alberto? vo5.
     
    #14 vvillovv, Sep 27, 2021
    Last edited: Sep 27, 2021
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  15. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I would never say that, lol. I bask in the glow of that light for about 5 months per year.
     
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  16. vvillovv

    vvillovv Senior Member

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    I'm gonna get a drew pro+bluetooth I swear but the bean counter wouldn't release funds yet. Can't say I blame anyone, but that is the plan, eventually. Till than the light stays lit and blinks sometimes too. Besides I need 2 brake piston rebuild kits and our super long life in at the low mark in both overflow tanks. Guess it's time to top them off too. Thanks to all you guys for what you do here.
     
  17. mr_guy_mann

    mr_guy_mann Senior Member

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    So, the TPMS sensors in each valve stem assembly periodically transmit pressure and ID info to the car. They transmit more often when the car is moving (active mode) and much less often when stopped (sleep mode). The car should turn on the warning light (solid) if the reported pressure is 20% or more below the rated (door sticker) pressure. A twist unique to Toyota is "initializing" the TPMS system- pushing and holding the reset button will have the system store the current pressure values as "standard-normal" for reference. (I assume that there is a range limit for this function- ie you can't set 15 psi as normal).

    If the light flashes a bit then stays on, then there is a fault with the system- 95%+ of the time a sensor is bad (or the ID wasn't programmed into the ecu). A "glitch" I do notice sometimes on older Toyota's (my 2006 prius and my wife's 2008 xB is that the light will come on solid after startup and will go out as soon as you drive and get above 20mph (when the sensors wake up and transmit)- pressures are on spec when checked.

    Posted via the PriusChat mobile app.
     
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  18. MPGboss

    MPGboss Junior Member

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    um just fill up tire pressure to 36 etc, reset tpms in the dash computer thing, and then the light goes away after a few miles as it realizes it's good to go, no?
     
  19. dig4dirt

    dig4dirt MoonGlow

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    Easy Peasy.
    I just refilled my tires for the cooler season and reset the TPMS
    40/38 psi
     
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