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Tire Presure Monitoring System (TPMS) question

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by thbjr, Dec 22, 2009.

  1. thbjr

    thbjr Member

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    Tomorrow I intend to go to my wifes work office (she works for a tire company) and fill my tires with Nitrogen. I will also be raising the tire presure from the current 35PSI to 42/40PSI. I am going to first deflate each tire and then refill with Nitrogen. When done, I'm thinking I will need to reset the TPMS as discribed on page 443 in the owners manual? Is that correct?
    Thanks,
    Tom
     
  2. hotbrass

    hotbrass New Member

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    If the car is off the whole time, and you dont rotate the tires, you probably wont have to reset it.
     
  3. Bobsprius

    Bobsprius BobPrius

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    I believe you should reset it, according to what the dealer told me. (Of course they could be wrong), but what was stated if you reset your tire pressures as you stated, you should also reset the TPMS to have a set point for the new pressures.

    Guess I will have to do some more research as well, since this is a good question.

    But from what I was preliminarily told, you should reset it since the old set point is still applicable??

    Hmmmm
     
  4. hotbrass

    hotbrass New Member

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    You dont have to reset it. But it will still be left with the lower pressure threshold. So if you are more worried about maintaining a high pressure more than just detecting a slow leak, then you should reset it. The sensors also have a maximum pressure rating, I just cant remember what it is, around 45psi I think.
     
  5. stream

    stream Senior Member

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    Since you are changing tire pressure, you should to reset it. It's no big deal--press and hold the button until the light on the dash blinks 3 times.
     
  6. rrolff

    rrolff Prius Surgeon

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    I believe the warning goes off when you drop like 10PSSI.

    The recommendation I saw elsewhere is to inflate to like 48, reset the TPMS sensors, then go to your 42/40 - this way you get a real notification...
     
  7. thbjr

    thbjr Member

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    Well, I took the car to put Nitrogen in the tires. I powered off the car, then deflated each tire to less than 10 PSI. I re-inflated them with Nitrogen up to 42/40. When I restarted the car, the TPMS warning light did not light up, so I drove the car home and after letting it sit for half and hour, reset the TPMS.
    I like the idea rrolff had about over inflating, setting the TPMS and then deflating them.
    I guess my biggest question is if the TPMS is activated by a difference in tire pressure, like loosing 10 PSI from the reset point, or at a preset pressure. The latter seemed to be the case with my Honda Fit. The TPMS light would come on at about 23 PSI regardless of how much air had been pumped into the tire. But then again, it didn't have any reset button that I'm aware of. When the light came on, I would refill the tire(s), take off down the road and within ohhh, I guess about 30 seconds, the warning light would go out.
    Tom
     
  8. hotbrass

    hotbrass New Member

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    Most pressure sensors work only within a certain range, like 20 to 35 lbs, or 25 to 45 lbs. If the pressure is outside the low end of the range it trips the return signal circuit. I dont know about Toyota, but they probably work the same way. But I dont know what the range is.
     
  9. stream

    stream Senior Member

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    This has been discussed here before--try a search. My recollection is it triggers if the pressure drops X% below where it was set.
     
  10. Bobsprius

    Bobsprius BobPrius

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    I thought the dealer informed me the threshold was 8 PSI??

    I did have a bad seal on a new tire when I took delivery of my 2010, and the next morning when starting the car the TPMS light was on.

    I checked the tire pressure and it was 24 PSI, so I believe it was set at 32 as the other tires were originally set at delivery.

    So maybe the 8 PSI was the threshold as they stated, but can't confirm from any written documentation.

    Also, like Rrolff's Idea! Will try that.

    Note: When the tire was taken off and resealed on the wheel the TPMS went off, they did not have to reset it.
     
  11. JimN

    JimN Let the games begin!

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    The TPMS will trip when pressure falls 25% of the set pressure. So, if set at 32psi when any tire drops to 24psi the idiot light comes on. Increasing the pressure to 42psi doesn't reset the sensor. It will still trip at 24psi. Reset the sensor and it trips at 31.5 psi.
     
  12. Bobsprius

    Bobsprius BobPrius

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    Thanks for the explanation...Makes great sense...

    So increasing the tire pressure 5-10 PSI makes good sense to reset the TPMS....

    Thanks for the info! :)
     
  13. bigcwill

    bigcwill Junior Member

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    Re: Tire Pressure Monitoring System (TPMS) question

    I was in Wal-Mart earlier and a sign listing their services stated resetting the tire pressure monitoring system would cost $20. Probably because it takes them 30 minutes to look it up in the manual.

    The system has already saved me twice with slow leaks due to nails and was able to make it to Sam's (where flats are free) before the spare had to be used.