TPMS MFD Light

Discussion in 'Gen 2 Prius Main Forum' started by ozarkretiree, Jun 16, 2021.

  1. ozarkretiree

    ozarkretiree Member

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    When my last set of Ecopia tires were installed by Firestone I had them remove the 4 wheel sensors. I had paid to have 2 of them replaced and decided I could do without TPMS, I have a good well used tire gauge. What I didn't realize is the system would still search for the sensors and when none are found it throws the light.
    Is there a way to safely disable the light or am I stuck with black electrical tape? I can't stand an issue light on the display.
     
  2. Skibob

    Skibob Senior Member

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    Black Electrical tape is the only fix.
     
  3. PriusCamper

    PriusCamper Senior Member

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    Well, you could put your TPMS sensors in a sealed jar that allows you to pump up the air pressure or you could find a way to send a signal to the car that's same as TPMS. I've not seen a way to disable that system in Toyota Techstream... But maybe @Elektroingenieur would have some thoughts on how to do it?
     
  4. fuzzy1

    fuzzy1 Senior Member

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    I'm not sure what is wrong with the black tape option. It is the easiest and cheapest solution, and also the easiest and cheapest and most reliable to un-do if you want it functional again or sell the car to someone who needs or wants it restored.

    As for indicator lights, I'm now resigned to always having some. Passenger airbag on/off indicator on both cars, clutch hill-holder function disabled indicator on the other car (after a half century of regular clutches, I just couldn't get used to that feature), headlights lights on, cruise control enabled, ...
     
    #4 fuzzy1, Jun 16, 2021
    Last edited: Jun 16, 2021
  5. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Even easier than electrical tape, is just let go of your consternation. There’s other constant-on lights, passenger seat air bag status for example. And the TPMS light is diminutive.

    We “endure” the TPMS light for about 5 months of the year, with our snow tires. Forget about it.
     
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  6. wjtracy

    wjtracy Senior Member

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    No easy fix for Gen2, Gen3 has a jumper fix to turn off the light.
    (1) But yes! I have shown a way here on PriusChat to generate a fake pressure reading on Gen2 OEM Denso TMPS with a big binder clip, but you still need a TPMS unit. Too lazy to search right now....all there with pics. Lasted 2 years for me,
    (2) Another temporary option is to reset the codes, and it takes a long drive >20-30 minutes for the system to realize the TMPS are dead. Some people who only take short trips can go a long time without the warning light coming back on
    (3) I thought it was illegal for Firestone to disable/take out TPMS.

    Anything beyond that is new territory.

    OK I got energy to search- this thread mentions all of the possible ideas I know
    TPMS Management with Techstream | PriusChat

    [​IMG]
     
    #6 wjtracy, Jun 17, 2021
    Last edited: Jun 17, 2021
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  7. mmmodem

    mmmodem Senior Taste Tester

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    +1
    I thought I "can't stand an issue light on the display" either. Turns out I can't stand looking for a piece of tape thick enough to block out the light even more. :whistle: I just lived with. Been 3 years now.
     
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  8. Elektroingenieur

    Elektroingenieur Senior Member

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    As far as I know, Toyota doesn’t provide customizable settings—able to be changed using a Toyota Techstream diagnostic system or otherwise—that would cause a vehicle not to conform to the relevant regulations. I imagine Toyota has no interest in leading its U.S. dealers, for example, into violating the “make inoperative” provision of federal law, 49 U.S.C. § 30122.

    I’m not aware of another easy way to disable the tire pressure warning system. The warning light in the combination meter is controlled by the tire pressure warning ECU over a multiplex (BEAN) bus, not a discrete wire, and I believe disconnecting the ECU would cause diagnostic trouble code B1247, Tire Pressure Monitor Receiver Communication Stop, to be stored.
    See @Stevewoods's posting in this thread, quoting at length a 2011 letter from NHTSA to the Tire Industry Association.
     
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  9. ozarkretiree

    ozarkretiree Member

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    Thanks to all respondents. Tape it is. Tightly integrated regulation compliance in Gen 2 Prius hybrid is understood and actually appreciated even when it can be a nuisance.
     
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  10. wjtracy

    wjtracy Senior Member

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    Note that in my thread above, @RobH once figured out how to reprogram the ECU for 5 TPMS, which leads to the question, can you do the same thing to reduce to zero or one TPMS? But not for the faint of heart.
     
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  11. Valiant V

    Valiant V Member

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    Does it throw a code if you "initialize" the TPWS with your existing (unused) sensors in a box in the back seat?

    From what I read in the manual (Gen 4, 2017), when you initialize them, it just uses whatever pressure they're under at the time - THEN notify you when it drops too low below that temp.

    If the system can work with 4 or 5 sensors depending on if you have a full-sized spare or not, it may well work with fewer (or no) sensors.

    Just a wild thought.....
     
  12. wjtracy

    wjtracy Senior Member

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    Well not sure.
    But if the TPMS sensor is working properly and transmitting, the system will read the low pressure and alarm right away.

    Now, take that sensor away from the car....you will see the old reading still in the register. Lets say its a good pressure 35.
    That will stay on the register for about 20-30 minute drive, until the system finally gets smart and realizes that is stale reading.
    Also if you reassign new bogus codes, eg 0000000 it will take 20-30 mins for the system to wise up.
     
  13. Valiant V

    Valiant V Member

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    That's quite some letter!

    Sounds to me that a savvy lawyer could make or defend an awful lot of liability cases based on all the great rules out there about safety equipment/systems on vehicles and digging into the condition of a vehicle at the time of an accident.

    Having see the cases that have been won against aircraft manufacturers (for crashes they really weren't at fault for), it certainly seems like there could be an awful lot of "targets" out there - any shop that ever touched the car.
     
  14. Valiant V

    Valiant V Member

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    Was just proposing that the system lets you know if the pressure drops from what it was initialized at. I do not know if the system is "smart" enough to interpret zero PSI and no change is a "loss of pressure" or not. I mean the correct pressure for the tires could be anything from the mid 20's to close to 50 PSI.
     
  15. wjtracy

    wjtracy Senior Member

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    Yes I think it possible via RESET button to set a higher alarm value when you first fill the tires, like 10% P drop. However, to be honest I did not experiment too much with the RESET button, so not sure.

    Toyota TPMS was really backwards. With Prius drivers so anal retentive abut tire pressure and MPG, you'd think they would give us the readings on the dashboard the way other cars do. My guess is japan drivers check pressure manually every week so they do not need the TPMS.
     
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