Restoring MPH/KPH switch on JDM/Aus vehicles (WIP)
 

Hi folks,
In some countries, Japan included, the cluster only displays that countries unit of speed measurement and cannot be switched between KPH/MPH, this sucks, because the hardwares all there to do it, it just needs fixing! so lets fix it!
There are 3 different elements preventing the cluster unit from properly allowing for switching between MPH and KPH, unfortunately far short of swapping head units entirely, all 3 elements need to be addressed before the functionality can be restored.

Element 1 : Physical switch
Easy mode:
Rather than go out of your way to manually re-eanble the KMH/MPH button, you can simply purchase the original part where the button was not blanked off, and has the "km/h MPH" print on the button, you can do this by purchasing the following :

subaru/toyota part #83001CA040

Hard(er) mode:
http://i.imgur.com/8RWmYih.jpg
This is mostly self explanatory, the reason the "Blank" button does not do anything is because the plastic for it has been molded with a lip that prevents it from moving or depressing the button, all we are doing is cracking open the button unit and shaving off a few mm of this lip to allow it to function properly again.

Note that the + and - are incorrectly marked on this old image, so ignore that.

Since it's a moving part, once you've shaved off a few mm, take care to work around the edge with a bit of sand paper or a fine file to make sure its smooth and able to move back and forth in the housing correctly.

Once that's done, you can re-install the button housing and rejoice at the unnamed button that can now be pressed.

Element 2 : PCB level components preventing the switch signal from reaching the brains of the cluster
This part took quite a while to properly diagnose, but here is what you will need to do:
https://i.imgur.com/s4afmCw.jpg

These are the 3 areas we will be working with.

Area 1
https://i.imgur.com/QW8EEnt.jpg
On some vehicles the top SMD component will be in place, but have a value of 000, replace this with a 2K SMD resistor (202)
Directly below it, will either be an empty space or a 47K SMD resistor (473), if it's empty, install a 473 SMD resistor
Directly below that, will be another empty space or a 5.6K SMD resistor (562), if its empty, install a 562 SMD resistor
To the right of these SMD resistors is a SOT23-6 transistor marked 15/F29, you *may* be able to get away with not installing this is you cannot source one.

Area 2
https://i.imgur.com/wZDcjz1.jpg
Here we need to check for two resistors.
The first is a 10K resistor, (103), if it is not there, add one.
The second is a 1K resistor, (102), again, if it not there, add it.

Area 3
https://i.imgur.com/0PaH66a.jpg
Here we are checking to see if C129 has a capacitor in place, if it does not, add one.
I used a 1uF capacitor to replace the missing capacitor, and it seems to have worked fine.

Element 3 : Enabling the function within the 93C66 Eeprom
The last piece of the puzzle is that, not only does the pcb lack a few components to handle the signal from the switch, that itself has been physically modified to not press under normal circumstances, but Toyota/Subaru also took it upon themselves to disable, in the actual eeprom, the support for the KPH/MPH switch.
after a pile of trial and error I can now provide you with the fix.

In the eeprom at offset 0x0000009C, for the Japanese clusters, you will see the following hex value
FDFF FDFF FDFF

This may be different on other region vehicles, but it will be F_FF F_FF F_FF in some manner.

In order to restore the functionality finally, change these bytes to:
F1FF F1FF F1FF

This is the flag in the eeprom to enable/disable this function, changing these bytes to the above enables the function, allowing everything to work as it should!


Sorry for the immensely long post, obviously if you're not decent as soldering, or don't want to dismantle your cluster, or you don't want to mess with your eeprom, and/or don't have a programming tool to read the current eeprom and write the modified eeprom, it's going to just make way more sense to just buy a cluster from a region that supports the MPH/KPH switch, which will net you the added bonus of also having MPH displayed on the physical printed cluster overlay, but i'm a stubborn idiot so I wanted to figure this out even if I no longer needed to know how!

Happy modding!

But... why?

because soon or later someones going to have a car that's restricted to one or the other that have imported the car and would like to change it over for the new locale, additionally, the fuel consumption only displays KM/L when locked to km, would be a hell of a lot easier to see the MPG with a working switch.

Lastly, cars that come with the ability to switch between the two are how the car was meant to be (why theres a third button to begin with), putting that functionality back can't be anything but a positive.

i love mods like this. i started pulling apart my cluster gauge to see if i could get that picture, but it looks like you have to remove the needles to get under the gauge faces to get access to screws to pull it all apart. I'm a bit too paranoid to mess with the needles right now so I'd rather not... but i hope someone else is willing to help you get that picture.

good catch on the LED spots. I might order some red leds to slap in there. should hopefully be pretty straightforward.

edit: never mind it looks like even with leds in there that the letters won't light up because it isn't transparent. still a good find though.

I took mine off when I redid my cluster, they are not too hard to reinstall.

The other issue is soldering the unlinked pins then adding the missing wires to the connector and linking them to the harness, though you could probably patch in to the interior light dimmer for both power and dimming.

I bought a spare switch cluster from my local dealership, will pull it apart today and see if I can locate buttons with transparency so we can swap them out and make em shine!

I actually have my blank button wired up to a shutter control remote for the gopro I have mounted on the dash so I can easily start/stop recording (until someone can post the requested pic!)

I have full confidence that once the missing smd's are installed the kmh/mph switch will work fully.

subbed. very interested in the outcome, good luck @Futaba

Restoring MPH/KPH switch on JDM/Aus vehicles (WIP)
 

I asked @pleong for some shots in another thread and luckily enough, he obliged. I hope this helps, seems it could remove a blocker on this!

Full credit to @pleong for the original pictures from this post.

http://i.imgur.com/saO3bQx.jpg
http://i.imgur.com/e8IUUVO.jpg
http://i.imgur.com/osnR0JC.jpg



@pleong, if you have a chance might you be able to snag a picture of this? I can see it here, but it seems to have some glare from the flash obscuring some stuff.

Thank you for the quick reply earlier as well!

Any update?


Sent from my iPhone using Tapatalk

I will be taking my Aussie BRZ to UK soon & would like to know what components need to be added to the pcb for the switch to work?

Ah crap, sorry lads! for whatever reason I didn't get any notifications when the thread received replies, let me look it over and i'll update in a few minutes, need to check the circuit and figure out the resistances!

Thanks for the assistance guys!

*edit* updated! you'll need the following to re-eanble the button on the PCB side:

1x 103 10K SMD resistor (size 1206 imperial?)
1x 102 1K SMD resistor (size 0603 imperial?)

Thanks Futaba, I assume R47 = 10K and R28 = 1K? Based on size of pads !!

I updated the original post with the exact locations for the two resistors you need to add :)

If you manage to pick up the resistors and attempt it before me, let us know if it works!
If for some reason it doesn't then we'll need to dig deeper and investigate for possible additional missing components or, more challengingly, possible changes to the ECU code, though I'm fairly confident that the resistors alone should be enough!

Great, Got that now. The components are probably same as used for other switch inputs to the logic. I wont be able to do this for a couple of weeks as I'm also ordering a new analog speedo dial from Lockwoods in UK
Thanks :)