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Kmh to MPH switch

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by Kolvorok, Sep 2, 2021.

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  1. Kolvorok

    Kolvorok New Member

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    Dear hive mind of the forum,

    I have an Italian Prius plugin 2015 that I am trying to import in the UK and I need to have it display the speed in MPH on the dashboard in order to be road legal.

    I saw in the instructions of the car that there is a switch on certain models that does that (see attached picture) but mine does not have it.

    IMG_1499.jpg

    I have also found the part (the switch) on the Toyota website. Cannot post the link due to the forum rules.

    Do you know where I can find the instructions to install said switch and whether it would work without a software/firmware modification?

    Thank you for your help!
     
    #1 Kolvorok, Sep 2, 2021
  2. bisco

    bisco cookie crumbler

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    I would have to guess no, because I have seen it asked in the past for other models, with no solution
     
    #2 bisco, Sep 2, 2021
  3. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    In North America, Prius of the 2016 model year of 4th gen (at least for a significant portion of the year) were not able to switch between miles-per-hour and kilometers-per-hour. Whatever you had, you were stuck with. I believe this was at odds with the owner's manual, which did talk about a method to switch.

    The issue was raised several times here, and no solution found. Toyota's response was to issue a "primer" on how to convert speeds, pretty pathetic.

    Addendum: doesn't seem to be any mention of switching speedometer units, at least in the 2016 North American Owner's Manual (PDF format) I have.

    That's really a poor example of "quality control" btw: how the hell did something that big get by Toyota's checking process...
     
    #3 Mendel Leisk, Sep 2, 2021
    Last edited: Sep 2, 2021
  4. Kolvorok

    Kolvorok New Member

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    Mine is effectively a 3rd gen Prius and 1st gen plugin. So I am not sure about the 4th generation, but in the UK (right hand steering wheel) apparently they are built with this button, probably because of issues with the border in Northern Ireland and the Republic of Ireland and different systems there.

    So, spoke to the US Toyota parts department and they confirmed that is the switch, the UK parts department too confirms that they can order it, but they cannot confirm whether it can be installed to my "cluster" as they are not knowledgeable about European cars.

    Gosh... we are all here because we care about mileage and fuel consumption, but all these protectionist barriers are causing more cars to be bought, built and scrapped than necessary, the emissions of all this waste cold easily be offset with a switch... it's an interesting thought.
     
    #4 Kolvorok, Sep 2, 2021
  5. Kolvorok

    Kolvorok New Member

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    I unearthed what I believe is the wiring diagram of that button to the instrument cluster. You can see attached the whole page and detail of the wiring of the pattern select switch. Does none know how to interpret this and whether it would work?
     

    Attached Files:

    #5 Kolvorok, Sep 4, 2021
  6. Kolvorok

    Kolvorok New Member

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    For reference, the part is this:
    Switch - Toyota (84721-47011)
    OEM Toyota Switch For 2012-2015 Toyota
     
    #6 Kolvorok, Sep 4, 2021
  7. QuantumFireball

    QuantumFireball Active Member

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    Dual unit speedometers have been standard there long before Ireland changed to metric speed limits (2005) as it is easy to travel elsewhere in Europe from the UK by ferry.

    My UK spec Prius Plug-in has the switch, however it also has a RHD instrument cluster which will be different to yours. If you shine a light on the display you should be able to see if the "MPH" segment is present on the VFD above or below "km/h". I guess after that you should check if any of the wiring to the location of the switch is present, otherwise you'd need to install that too.
     
    #7 QuantumFireball, Sep 6, 2021
  8. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Funny thing is, it USED to be trivial; manufacturers just printed both units on the mechanical speedometer.
     
    #8 Mendel Leisk, Sep 6, 2021
  9. ChapmanF

    ChapmanF Senior Member

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    Before spending any money on the switch, you could look at the combination meter to see if there is any wire attached at pin 2 of that (A) connector (your second attachment shows the connector designations that go with the (A), (B), and (C), but it's too small for me to read them).

    You could poke a small wire in there and touch it to body ground, and see whether your display switches between miles and km each time you do.
     
    #9 ChapmanF, Sep 6, 2021
    QuantumFireball and JohnPrius3005 like this.
  10. QuantumFireball

    QuantumFireball Active Member

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    In the OP's case, they would still have a km/h-only speedo which is the norm in the European market (outside the UK). For registration in the UK they would need to add MPH units with stickers, or replace the instrument cluster if it was analogue.
     
    #10 QuantumFireball, Sep 7, 2021
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