tire low pressure light is always on

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by southjerseycraig, Sep 21, 2021.

  1. southjerseycraig

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    The low tire pressure light is always on in my 2010 Prius even though the tires are fully filled. I know with at least one other manufacturer, it costs a lot to get this repaired. Do any of you have an idea as to how much it would cost to have this problem solved? I would like to do that because the low-pressure light is a safety item (I want to know if there is a problem with a tire), but there's a limit to how much I would be willing to pay. Thanks in advance!!
     
  2. G Man v5

    G Man v5 Member

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    Very good chance one or more of the batteries have failed. AFAIK, these batteries are not replaceable. You can buy aftermarket sensors. Would be best to replace all four.
     
  3. jzchen

    jzchen Senior Member

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    Within the last year I bought a Dorman replacement transmitter and had a local Walmart auto center install it. I did need to read and program the sensor ID with my TPMS tool.
     
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  4. burrito

    burrito Member

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    Each tire has a TPMS device which wirelessly connects to the car's computer to report the tire pressure. They can fail and batteries can die. They also should be recalibrated to the car when you change your tires (or get new TPMS sensors).

    There's a button under the steering wheel near the driver's feet that is used to recalibrate. This is an easy problem to rule out prior to spending money on other fixes. There should be instructions in the owner's manual you can follow (or just search YouTube), but make sure the tire pressure is actually correct before you do this.
     
  5. sam spade 2

    sam spade 2 Senior Member

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    Ask a dealer.
    Then check with a few tire shops.
    It is a fairly common problem.......and the cost to fix it is what it IS.

    And......while having that monitor working is nice, there are MILLIONS AND MILLIONS of cars on the road without it.
     
  6. bisco

    bisco cookie crumbler

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    put a piece of electrical tape over it
     
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  7. Paul E. Highway

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    In Hawaii, you can't pass safety check with TPMS light showing. My 2010 (sold new in mid 2009) was sold to me in 2019 with the TPMS light on. There are some DIY hacks on YouTube but I just took it to tire shop and got it done. You're ahead of the game, almost 12 years!
     
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  8. fuzzy1

    fuzzy1 Senior Member

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    New sensors need to have their ID codes programmed into the car, but can't be done with that recalibration button. It must be done with a tool (very many choices available) that plugs in to the OBDII port. Any tire shop should include this as part of their installation service.

    The under-dash recalibration button just resets the pressure thresholds of the alarm. Despite having two different seasonal wheel sets with different sensors, I haven't done this reset, and have had no known problems from not doing so.

    I'd start with tire shops first, only go to $tealer$hip$ a$ a la$t re$ort. They can quickly determine if any sensor(s) has a dead battery or has otherwise ended its life. If so, the cost to fix is the price of the replacement sensor (~$45-75) plus the cost to install it, which involves dismounting and remounting the tire on the wheel rim.

    I've had intermittent spurious TPMS warnings on my 2012, from still unknown cause. So I won't rule out a system problem with the car. That is why it is probably worthwhile to have a tire shop first read out each sensor to check for failures, before blindly buying new sensors.
     
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  9. southjerseycraig

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    So I take it there are four sensors, one for each tire. The odds are that only one has failed, and that one is causing the low pressure light to come on. So here's the question: when I replace a bulb in a ceiling fixture, I replace all of them, figuring that the rest probably don't have long to live Similarly, should I have all four sensors replaced at once on the theory that the others will probably fail shortly, too?

    Thanks to everyone for helping.
     
  10. burrito

    burrito Member

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    They cost quite a bit more than light bulbs, so I'd say it's not worth the expense. Only change the ones that are non-functional.
     
  11. jzchen

    jzchen Senior Member

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    As reference I only changed the offending (low battery) 1 in my '14 iQ with 15k mi. I replaced all four in our '12 Prius v (along with 4 new tires) at around 30k mi.

    My Autel ITS600 reads battery level and somehow that was the correct decision for the '12. (I did the change to new sensors before I bought the Autel tool). The iQ I had to find the offending sensor and I brought the loose wheel to Walmart. Hopefully the shop you take it to can read battery level and you could go from there...
     
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  12. rjparker

    rjparker Senior Member

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    The sensors have not broken. They have an internal battery. So, yes they will all go out shortly because the problem is 95% low internal battery. Costco changes and programs them to your car for a reasonable price.
     
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  13. sam spade 2

    sam spade 2 Senior Member

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    Yes but for a much better reason.
    Those sensors contain little batteries that eventually go dead no matter what you do.
    The other 3 are MUCH more likely to fail soon after than the light bulbs in your example.
    I will be happy to take those used bulbs off your hands !!! :)
     
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  14. fuzzy1

    fuzzy1 Senior Member

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    On the TPMS issue, I'd say that the 'replace 1 or all' question depends on several things, including the age of the sensors, how long you plan to keep the car, and when you expect to next replace the tires.

    If the sensors are original from the factory, then they are likely all headed towards battery death in the near future. This pushes for replacing them all.

    If the sensors are younger than that, like under 5 to 7? years, then it likely had some defect or injury, so I'd be inclined to change just the bad one. Or you if plan on replacing tires in the next year, it could well be reasonable to wait until then, saving on the labor to replace. Replacing sensors concurrent with a tire change should be done for just the price of new sensors, with no extra labor charge.

    On the light bulb issue, I've never had to deal with fixtures that were both multi-bulb and hard to reach, so didn't use that practice. I can see where is makes some sense with the old era incandescent bulbs. But since everyone should have either upgraded to LEDs by now, or still be in process of gradually replacing aging CFLs with LEDs (all our legacy ceiling bulb fixtures have been replaced with flush-mount LED disks or panels), this wouldn't really apply anymore.

    And to add more detail:

    With help from an updated ScanGauge-II to read out individual tire pressures, I traced my issue to a single sensor going unread for long enough to trigger a warning because the TPMS thought it was missing or dead. But then it would reappear within 20 minutes. It might repeat several times over a single long trip, then not happen again for most of a year. The first two episodes were just a couple weeks apart, but on separate wheel sets, just before and after a winter tire swap. With reduced driving, it hasn't reoccurred since the start of the pandemic.

    I haven't been diligent enough to track the failure to specific sensors (one on winter tire set, another on summer set) vs a specific corner of the car (e.g. antenna reception signal strength issues) following tire rotations. Neither the ScanGauge-II nor the car know which sensor is at which corner, so I'd need suss that out separately.
     
    #14 fuzzy1, Sep 22, 2021
    Last edited: Sep 22, 2021
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  15. southjerseycraig

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    Thank you so much. I want to make sure I understand. Let's suppose there has been battery death. Is there a way that a new battery can be installed, or does the sensor have to be replaced?
     
  16. sam spade 2

    sam spade 2 Senior Member

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    They are not designed to have the battery alone replaced.
    They "live" in a pretty harsh environment too.......so going to extraordinary lengths to just replace the battery probably is not a good idea.
     
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  17. fuzzy1

    fuzzy1 Senior Member

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    I believe that nearly all of them have a sealed-in, non-replaceable battery. Besides the very obvious 'benefit' to the manufacturers of selling more sensors, it also reduces initial sensor cost and gets rid of several reliability issues and failure mechanisms that come with making the battery replaceable. As mentioned above, it is a harsh environment, so the electronics really need to be sealed.
     
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  18. southjerseycraig

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    Thanks! I now understand better. Yes, sealing the battery makes a *lot* of sense. I take it that the battery in each sensor can be tested to figure out which sensor or sensors need replacement, and that I shouldn't let them replace sensors without testing first.
     
  19. fuzzy1

    fuzzy1 Senior Member

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    The tire shops have an RF reader tool that is placed against the sidewall next to the sensor, and reads out all the details. (They also have an OBDII plug to reprogram these IDs into the car.) Each sensor transmits its ID code, pressure, temperature, and possibly (?) battery level. Quick and easy.

    But the real test is if a particular sensor transmits anything at all. With a dead battery, it goes missing, undetectable.

    I have my own TPMS reader / programmer tools (separate RF reader and OBDII programmer), so can find it myself. But drivers with just one TPMS car in the household, or who don't have separate summer / winter wheel sets that need to be reprogrammed twice a year, won't be able to justify the tool cost.
     
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  20. southjerseycraig

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    Thank you so much. Please forgive a basic question: if a sensor isn't transmitting, would that cause the low pressure light to be on all the time?
     
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