TPMS light should be OFF

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Frontporch, Dec 16, 2025 at 4:01 PM.

  1. Frontporch

    Frontporch Active Member

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    I replaced my TPMS sensors in each tire this summer.... Worked without issue for months.

    The light is now on and I immediately assumed that a cheap sensor was bad. Connected techstream and saw several pressure values. All seemed reasonable. It looks like the Low threshold (sorry I dont remember the name) was around 26 PSI. I think all of my tires were around 31-34 PSI and some other indicator pressure (there were four values) were all slightly different but very high... 28-30.

    I would like to do a sensible reset of this system. If I verify all cold pressures are around 35PSI should I be able to use the TPMS reset to get that light off? Not really sure how it works. I didn't find it in the owner's manual at first glance. I also saw temp readings that were similar to the outside temp 30 degrees. I hope cold is good for a reset.

    Thanks!
     
    #1 Frontporch, Dec 16, 2025 at 4:01 PM
  2. bisco

    bisco cookie crumbler

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    idk, but definitely put a gauge on the tyres, cold makes the pressure drop
     
    #2 bisco, Dec 16, 2025 at 4:09 PM
  3. Brian1954

    Brian1954 Senior Member

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    Post a picture taken of the Techstream data for the tire sensors.
     
    #3 Brian1954, Dec 16, 2025 at 6:25 PM
  4. Tombukt2

    Tombukt2 Senior Member

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    Thot in very 28 the tire info.is on main screen .the screen that shows health at top . Tells me what ea sensor is reading by number 1234
     
    #4 Tombukt2, Dec 16, 2025 at 8:57 PM
  5. priumium

    priumium Member

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    Do a health check and validate if you have a current or historical TPMs code.

    Light will stay on with historical codes, for example if one sensor went into sleep mode and did not communicate within 20mins, dtc is set and the light will be on for 20 cycles apx, unless cleared.

    None of your mentioned values are below 26, so seems ok unless the temperature sensor part is invalid/wrong.

    Your described concept for resetting the minimum threshold value is correct, however it will unlikely remove the light. Check the actual reason is step one, especially since you have TS ready!
     
    #5 priumium, Dec 17, 2025 at 4:54 AM
  6. Frontporch

    Frontporch Active Member

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    IMG_9954.jpeg
     
    #6 Frontporch, Dec 18, 2025 at 3:49 PM
  7. Brian1954

    Brian1954 Senior Member

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    All the tire sensor data looks okay in the picture. Was the low tire pressure light on when you took the picture?

    What is the trouble code(s) shown in techstream? Post a picture please after running a health check.


    SM-S931U1 ?
     
    #7 Brian1954, Dec 18, 2025 at 4:15 PM
  8. ChapmanF

    ChapmanF Senior Member

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    That live screen shows 0 for Number of DTC. So there don't seem to be any DTCs at that moment. If the warning light was on right then, I'd be at a loss to say why.
     
    #8 ChapmanF, Dec 18, 2025 at 4:31 PM
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  9. Brian1954

    Brian1954 Senior Member

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    I missed that when I looked at the data in the picture. Nice find.

    Posted via the PriusChat mobile app.
     
    #9 Brian1954, Dec 18, 2025 at 4:49 PM
  10. Tombukt2

    Tombukt2 Senior Member

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    I'm just interested if you had a code at all and what it was when it was..
     
    #10 Tombukt2, Dec 18, 2025 at 7:06 PM
  11. Frontporch

    Frontporch Active Member

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    The light has been on for over a week.
     
    #11 Frontporch, Dec 18, 2025 at 11:07 PM
  12. Brian1954

    Brian1954 Senior Member

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    Does that mean the low tire pressure light was on today (Thursday) when you used Techstream to look at the live data and took the picture?

    If the light is still on, please run health check and post a picture of the results and take a picture of the dash showing the light. Also accesss the live data for the tire pressure sensors again and take another picture. Thank you.
     
    #12 Brian1954, Dec 18, 2025 at 11:35 PM
    Last edited: Dec 18, 2025 at 11:51 PM
  13. priumium

    priumium Member

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    Zero DTC means zero current DTCs.

    I would assume there is a historical code lingering, but the OP would naturally have checked this by clicking Trouble Codes I would also assume…:)

    In the event there is no HIST code I would suggest any or all of these;

    1. entering all IDs again in the Utility screen as this may force a more complete recheck.
    2. wipe DTC/FF memory regardless, on the main screen, or disconnect negative battery cable for 2 minutes.
    3. Release 25% and re-add pressure on all four tires.
     
    #13 priumium, Dec 19, 2025 at 7:27 AM
  14. Frontporch

    Frontporch Active Member

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    It’s very crappy weather today but I will look into some of he suggestions tomorrow and try working with the pressures more.

    the light was on when I took that picture with techstream. I hooked up the computer after getting home from a 20 minute drive

    just for my knowledge if I were to inflate to 40 psi and press the TPMs reset would that change the initial threshold of low pressure to be some percent of the current 40 psi for all tires? Does dropping below that value trigger the light or does any one tire have to fall below the other lower limit of 25.4 psi
     
    #14 Frontporch, Dec 19, 2025 at 8:34 AM
  15. ChapmanF

    ChapmanF Senior Member

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    yes

    yes

    that minimum limit is just the lowest it will allow you to set any alarm threshold (say, if you were to press the SET button while a tire was flat, it wouldn't set the alarm threshold to 0 for that tire, but to the minimum threshold).
     
    #15 ChapmanF, Dec 19, 2025 at 9:41 AM
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  16. priumium

    priumium Member

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    But, for informational purposes, if you deflate all tires to 20 psi and press reset button, ECU logic would set low pressure at around 15 psi and ignore lower limit. Likely a big bug, attest in my firmware.

    The concept is 25% of the lowest pressure unless below limit mentioned.

    This is just for testing information. Never run car deflated below 35? Psi / 2.3 bars EU.
     
    #16 priumium, Dec 19, 2025 at 11:28 AM
    Last edited: Dec 19, 2025 at 11:34 AM
  17. Brian1954

    Brian1954 Senior Member

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    That is very weird because the DTC that is shown on the picture is 0 which means that there are no tire pressure sensor errors detected. The low tire pressure light should not be on.

    I would not reset the minimum tire pressure threshold just yet.

    Can you please take a picture of the dash showing the light. Thank you.


    Posted via the PriusChat mobile app.
     
    #17 Brian1954, Dec 19, 2025 at 11:37 AM
  18. Tombukt2

    Tombukt2 Senior Member

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    Where is this car do you have the normal PO420 code??.
     
    #18 Tombukt2, Dec 19, 2025 at 12:14 PM
  19. ChapmanF

    ChapmanF Senior Member

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    in what sense is P0420 normal?
     
    #19 ChapmanF, Dec 19, 2025 at 12:32 PM
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