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Found A New Way To Check Tire Pressure

Discussion in 'Gen III 2010+ Prius Care, Maintenance and Troubles' started by The Critic, Dec 31, 2011.

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  1. The Critic

    The Critic Resident Critic

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    [​IMG]

    This is for amusement only, but I've gotta say that it is so much quicker and easier than getting out my pressure gauge. ;)

    Interestingly enough, Techstream gives you the option for a "compensation tire pressure." It asked me what the factory specified pressures were for the front and rear, the ambient temperature, as well as whether the car was: a) cold (sitting for more than 4 hours), b) driven on short trips, c) just parked after extended highway driving (more than one hour). After entering the appropriate values, Techstream gave me readings of 38.5 F and 36.5 R. I am not sure what the software is using as a baseline, but I think those values are indeed fairly close to the true cold pressure that I would have measured.

    I am curious though, how accurate are the pressures being reported. The readings said my rear tires were 41 psi, but I measured 39 psi with my gauge. If the sensors' readings are correct, that means I need a new gauge.

    Overall, this function is probably of little value to most people, and I posted this just because I thought the function was pretty cool. What I do recommend to all of you DIYers though, is to spend the $60 for the knockoff Mangoose cable so that you can get Techstream working for diagnostic use. I must give credit to pjksr02 for directing me to the Mangoose cable and for guiding me through the setup process. :rockon:
    2 people like this.
  2. xs650

    xs650 Senior Member

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    Would there be some way to program a ScangaugeII to read those pressures?
  3. pjksr02

    pjksr02 Member

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    I've found my two pressure gauges vary from the TPMS readings, too. Each reads lower by about 10-15%. Remember, the tire pressure warning system is set off by changes in pressure, so I wouldn't conclude the sensors are more accurate.

    I think it's a shame Toyota's TPMS system requires owners to pay up, or jump through hoops to correct errors or to register new sensors.
  4. RobH

    RobH Senior Member

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    I found that the TPMS sensors in the wheels vary as well. I set my tires to 42.0 front, 40.0 rear with a tire pressure guage. They read back via TPMS as 42.0, 43.1, 40.6, and 41.0. So the difference between my gauge and the sensors varies from 0.0 up to 1.1 pounds.
  5. The Critic

    The Critic Resident Critic

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    How are you reaching those values? For instance if you desire 42 psi, you should inflate to 44 or 45 psi, and slowly let the air out in 0.5 psi increments until you reach 42.
  6. wick1ert

    wick1ert Senior Member

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    I set mine recently to 40/38 per my pressure gauge (I tend to go just a smidge over the marker line) and apparently I did pretty well. I did happen to set the pressures when it was around 48 degrees outside, so once the temps drop into the 30s, I should probably review them again.

    Critic - FYI, if you download DeskPDF (it's a free PDF printer driver) you can print the data in an adobe file for easier viewing later on. Not sure if you have anything similar or not, but just in case you might be interested.

    Attached Files:

  7. Mickduc

    Mickduc New Member

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    Is there a comprehensive thread on getting Techstream to work with the Mangoose cable and the costs involved?
  8. wick1ert

    wick1ert Senior Member

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    None that I'm aware of. The Mangoose has been on sale recently for as low as $60 online. It comes with drivers and a copy of TechStream.

    With TS, you have a few options: You can pay to register it, use a work-around to use it in evaluation version, or scour the internet and find a way to use it without paying.

    Other than that, the hardest part is figuring out how to navigate the program and knowing what is where.
  9. The Critic

    The Critic Resident Critic

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    Thanks, I will look into that. You should also remove your VIN from the PDF before posting. :p
  10. wick1ert

    wick1ert Senior Member

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    Oops, thanks for pointing that out. I just fixed it and converted to word doc, too.
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