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Can the Tire Pressure Warning Light Be Modified?

Discussion in 'Gen 3 Prius Main Forum' started by Johnny Cakes, Dec 4, 2022.

  1. Johnny Cakes

    Johnny Cakes Senior Member

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    A few questions about the tire pressure warning light....

    1. Can the trigger value be modified wih Techsream or something like that?

    2. What is the factory trigger pressure?

    3. While correct pressure is obviously best and any deviation is not optimal, at what pressure do you begin to do damage to the tires

    Thanks!
     
  2. ChapmanF

    ChapmanF Senior Member

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    The alarm trigger pressure can be set with a small pushbutton (labeled SET) that you will find under the dash on the driver's side.

    It doesn't let you set the trigger pressure directly. What you do is, you inflate all tires to your desired pressure, and then you turn the car on and hold the SET button, and it sees the current pressure in all four tires, and it sets the four trigger limits to a certain fraction below each pressure.

    I did something a little different with mine: I don't really like how far below the desired pressure it sets the limit. If you inflate the tires to the factory-recommended 35 psi/33 psi, and use the SET button, the threshold pressure ends up somewhere in the 20s. (I think you can see, in Techstream, the threshold pressure that ended up getting chosen. But this indirect method with the SET button is the only way to adjust it.)

    What I did with mine is I first inflated my tires to 44 psi, much higher than I intend to run them. Then I used the SET button, and the thresholds got set around 34 psi. I like to run pressures around 38 and 36, so this means I get warned right away at just a few psi low. That's the way I like it, even though it means getting the warning light pretty often. I have a pump on board, so it's never a big deal to add some air when the light comes on.

    I also didn't bother having the front pressure higher than the rear when I used SET. I just had all four the same pressure, so all four alarm thresholds are the same. If you want to set in the 2 psi front/rear difference, then you have to fuss with the SET button again at every rotation. Too much fuss for me.
     
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  3. ASRDogman

    ASRDogman Senior Member

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    After setting the desired pressure for each tire, you press and hold the reset button,
    press the start button (or do you press the brake pedal? I don't remember).
    The tire pressure warning light will start flashing several times.
    When it finishes, you can release the button.

    Whether it's 20psi or 60psi, when it falls a few pounds below that, the light comes on.
    Twice I had tires with nails in them. I don't know how long they were in the tire, but when
    the light came, I stopped, started checking pressures, and both times it was 20 pounds.
    About 16-18 pounds below what I set. But I could few the car not handling the same.
     
  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    This is very much a function of speed, and there is variability from tire to tire. At walking speed, any tires will last for years at 5psi. At highway speed, low 20s (psi) can be enough to cause lasting problems.
     
  5. Johnny Cakes

    Johnny Cakes Senior Member

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    Could you please be more specific? I'm not seeing it.
     
  6. jerrymildred

    jerrymildred Senior Member

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    Screenshot 2022-12-22 at 8.33.15 AM.png Screenshot 2022-12-22 at 8.33.41 AM.png
     
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