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TPM Problem -- where is it?

Discussion in 'Gen 2 Prius Main Forum' started by cyberpriusII, Apr 20, 2011.

  1. cyberpriusII

    cyberpriusII Prodigyplace says I'm Super Kris

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    Well, here's the would-be bride, back for more (opps, probably should rephrase that, but...).

    Bear with me. I drove out one day and noticed the TPM light was on. Stopped, all looked good, but about 10 minutes later reached town and stopped at the tire shed (it really is a shed).

    The good old boys kicked around a bit, shrugged, hhrumped and finally pronounced no real problem and put air in all around.

    The light went out.

    I had no idea how much PSI, they are nice guys, but haven't really got into the equality thing yet. They also prefer to work on Ford and Dodge pickups.

    I rotated said tires a few days later and broke my round dial gauge before I could check pressure. Finally got a Meier Accu-gauge today and found all four tires at 40.

    Put them at 33 rear and 35 front per the sticker on the door (I know, but the car rides better at 33/35). The TPM did not go on.

    It worked a week or two ago. All that has happened is I rotated said tires. What's the problem. Should not have it went on....I really like that light -- sorta -- :confused:

    Opps, again, I meant to post in Troubleshooting, etal. Sorry....
     
    #1 cyberpriusII, Apr 20, 2011
  2. dogfriend

    dogfriend Human - Animal Hybrid

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    The TPMS light is supposed to come on when the pressure in one or more of the tires drops a certain amount below the "set" pressure. I forget what percent low (maybe 30%?) but it is quite a drop. I'm thinking that you had a low tire (30% lower than 35psi = ~ 20psi) before the good old boys refilled it.

    I wouldn't worry about it unless the light comes back - in that case, check all 4 tires with your new tire gauge.

    BTW, I set my "set" pressure at 40/38 and the only time my TPMS light ever came on was when I got a set of replacement tires and they set the pressure to 33 on the rear. I inflated the tires to 38 again and the light went out.
     
    #2 dogfriend, Apr 20, 2011
  3. brick

    brick Active Member

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    Have you tried resetting the system at the proper pressure? Could be that the TPMS was reset at some higher pressure than you are using now, so "normal" pressure looks low and trips the light. (Just set the tires to the right pressure and then hold down the TPMS button for a few seconds. I think the light blinks while it is adjusting its settings.)
     
    #3 brick, Apr 21, 2011
  4. David Beale

    David Beale Senior Member

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    Fill the tyres to the pressure you want to run at.
    Press the TPMS button under the steering wheel and hold it depressed until the car beeps at you. There are two buttons down there, one is TPMS set, and the other is SKS off/on.
    Now the light won't come on until -any tyre- drops 20% below whatever pressure was in it when you pressed and held the TPMS set button. So each tyre can have a different pressure threshold. This is why it's important to check them and set them accurately.

    DO check the tyre pressure regularly (at least once a month). Just because you have a TPMS doesn't mean you can get lazy. ;)
     
    #4 David Beale, Apr 21, 2011
  5. cyberpriusII

    cyberpriusII Prodigyplace says I'm Super Kris

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    Thanks, guys for the tips. :D

    I guess I will go ahead and reset the TPM system.

    But, darn, I KNOW I SHOULD check the pressure my self, but I sure prefer being lazy and relying on the idiot light!! :p
     
    #5 cyberpriusII, Apr 22, 2011
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