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Tire Pressure Light On

Discussion in 'Gen III 2010+ Prius Care, Maintenance and Troubles' started by jangell2, Jan 4, 2010.

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  1. jangell2

    jangell2 Junior Member

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    The tire pressure light came on solid, indicating low pressure and not a malfunction with the system. I've looked at the prius in the garage and can't see any tires that are low. We've been driving with the pressure as is from the dealer.

    I find it a little suspicious that this happens when the weather has turned quite cold, in the low 30's and lower sometimes.

    If I check my tire pressure and add any required air, will the pressure light go out on it's own?
  2. john1701a

    john1701a Prius Guru

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    That's normal. You lose about 1 PSI for every 10°F degrees.

    Also, air naturally leaks out over time, causing even lower PSI. Something you typically will not noticed, since tires hold their shape so well nowadays.

    As for driving with pressure the dealer set, that's asking for trouble. They barely set to minimum in the first place.

    If you haven't checked (cold measure) in awhile and the warning is on, you're dangerously low. That's 25% below the automaker recommendation, a known compromise by federal safety standards.
    .
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  3. Bobsprius

    Bobsprius BobPrius

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    Jangell2,

    Since the warning indicator is on, use a accurate Tire Pressure Guage and check all 4 tires. You will find which one is low.

    I had it happen to me once as well. But, could not see the tire that was low as well, but when I used a good digital guage I found the tire easily and it was at 22 PSI and should have been at 32 PSI.

    I believe the TPMS system will alert once there is about a 6-8 PSI drop from set pressures.

    Once you have added the correct amount of air to match the placard on your driver door jamb, your light should go out soon thereafter.

    Hope that helps.
    Bob :)
  4. jangell2

    jangell2 Junior Member

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    The manual says to check the pressure cold, not having driven for 3 hours. How important is that? I got to drive to an air station anyway. I figure I'll go out and get a good digital gauge tomorrow too.
  5. pjksr02

    pjksr02 Member

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    Let us know how you make out.

    For anyone following this thread, who wants to know a bit more on how the system works, Toyota has a bulletin on initializing the TPMS. I'll post a link below, but if the link gets "broken," the TSB is numbered T-SB-0151-09, and applies to several Toyota models. See also T-SB-0345-08, regarding cold-weather.


    http://priustouringclub.net/librairie/mediatheque/pdf/Prius3_2010_owner_manual/Maintenance%20and%20Care/Tire%20Pressure%20Warning%20System%20Activation%20and%20Initialization.pdf
  6. Tom183

    Tom183 New Member

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    Believe the light - TPMS works. One (or more) of your tires is now more than 8lbs below the "set point".

    The set point is whatever the pressure was when the system was initialized - and if the dealer set it at 35lbs front / 33lbs rear, that means one of your tires is under 27lbs or possibly even under 25lbs.

    It's possible that the system was initialized with a warm tire - i.e: WRONG - and now that cold weather has hit (and your tires are cooling down), the cold tire pressure is that low.
  7. qbee42

    qbee42 My other car is a boat

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    Measuring the pressure with cold tires removes some of the variability. Hot tires will run a few psi higher, but there is no way to know exactly how much higher they should be. Filling them hot is better than not filling them at all, but to be accurate, recheck the pressure later when the tires have cooled.

    Tom
  8. jangell2

    jangell2 Junior Member

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    Sorry to be tardy in updating with my results. I guess it was Monday I went to Napa and bought the only digital guage they had on the shelf. Then I drove to a Shell that I knew had air and it was out of order. I then drove to a Valero and their air was out of order too. Now I'm getting miffed.

    I find a Citgo that has air and it is digital, you set it to the pressure you want and it pumps up the tire to that. It was good I had the Citgo system since the new guage quite working after doing two tires. After inflating the tires per the Citgo settings, the warning light went out immediately.

    I went back to Napa and bought a better digital guage they had in the back. It didn't work because the batteries needed replacing which Napa did. I walked out to my car and found that I would have to turn it off to zero it out each time, which would be a pain. So I returned it.

    For the moment I'm assuming I've got the pressure close enough. Tomorrow, I'll check the tires with a new guage I got from Amazon. It's an Accutire Racing Tire Pressure Gauge. The comments were mostly positive on Amazon. It measures from 0-60 psi in increments of .1.

    Has anyone run accross an inexpensive, but quality tire inflator for home use? It seems like that's the only way I'll get accurate inflation, otherwise I have to drive to get the air.

    My travails aren't quite over. We've noticed on our credit card that the credits for the returned guages have shown up, though the charges have. If I don't see them by Monday, I guess I'll have to call them.
  9. Joe166

    Joe166 New Member

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    Advance Auto Parts has a cheap, small inflator on sale. It is pretty small...about 8 inches square and less than two iinches thick. It is ordinarily about $16 and is still shown at that price but it rings up at $9.88 or thereabouts which is the price shown on the current flyer. Works fine. The built in gauge stinks, but it will pump up to more than we need even for the compact spare.

    It may not be the fanciest or most quality inflator but it works and it is small. What else do you need? Yeah, I know...nothing but the best for my sweetums. I also use a $2 slide air gauge that is short so it fits inside the gas tank cover so it is always available and when it breaks, it breaks.
  10. pjksr02

    pjksr02 Member

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    Sears has a good, cheap gauge, too. If you can get a GH Meiser gauge, you're doing well, though they're all made in China nowadays...

    This saga is a great reason to invest in an air compressor for home, if you need an excuse w/ your significant other!
  11. qbee42

    qbee42 My other car is a boat

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    You might consider one of the combination units that have a booster battery and an inflater. They can be a lifesaver if you ever accidentally discharge your 12V battery by leaving a light on, or the hatch open.

    Tom
  12. jangell2

    jangell2 Junior Member

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  13. yardman 49

    yardman 49 Active Member

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    That unit is probably overkill for your needs. Check out Tom's (qbee) suggestion, and look for a combination battery jumper/tire inflator.
  14. tumbleweed

    tumbleweed Senior Member

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    I think the digital gauges are just analog gauges with a digital readout. I buy good quality analog gauges, no batteries, and they seem to do just fine, + or - 1 pound is close enough.

    Check some of the threads here on tire pressure, you might find you want to use higher than the Toyota recommended pressures.
  15. jangell2

    jangell2 Junior Member

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    I just got back from the dealer after our first 5K service and checked the tire pressure so these are not cold readings. Will wait 3 hours and do them again. The LF tire valve seems to a little difficult to access and I may have bled air out before getting a reading.
    LF-33.7 RF-34.9
    LR-34.9 RR-35.5

    Assuming I bled a too much air on the LF, it looks like they filled all the tires to about 35. The door jam sticker recommends 35 front and 33 rear.
  16. Tom183

    Tom183 New Member

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    Warm tire reading 35lbs is a cold tire reading of 32lbs or less... Your rears look fine but the fronts likely need more air.
  17. qbee42

    qbee42 My other car is a boat

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    There are many pressure sensing ICs available. Generally digital pressure gauges use IC pressure transducers, as they are cheaper than building from scratch. Accuracy can vary from garden variety crappy to astonishingly accurate, depending on what you are willing to pay.

    Tom
  18. Smirv

    Smirv AkA: Ryan

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    Is this ^ done by the dealer or am I supposed to? I had a 600+ mile roadtrip this weekend and in the beginning of the trip the TP light did the blink then solid thing which indicates a malfunction in the system. It did it once more a few minutes later then nothing the rest of the way or the return. Checked my pressure, all was good. Should I take it in or did it correct itself?? Thanks.
  19. stream

    stream Senior Member

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    As indicated in the TSB ;) the dealer needs to activate the sensors during PDS. Then they also initialize the system.

    The initialization also need to be done by the owner any time they change tire pressure.

    If you've had no issues until now, my guess is the dealer did the activation & initialization during PDS, and now you may have a system issue.
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  20. tumbleweed

    tumbleweed Senior Member

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    If it is not malfunctioning it will not do any good to take it in. They will just check the tires, reset it, and tell you it's OK. You have already done that.

    You may well have an intermittent failure but if it's not broke when they look at it they will do nothing. If it is a malfunction it will probably break again and maybe it will stay broken so you can have it fixed, but the important thing is your tire pressures are OK, just check them often.
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