How to enable WiFi Tethering for MVNO (or any) SIM on DoCoMo Android Phones.

So you have either switched to an MVNO (like Mineo or OCN), or had your phone unlocked by DoCoMo (or elsewhere), and you are happy.  You have a cheap plan and/or you can use your phone all around the world, except...

When you try to use WiFi Tethering, it comes back with an error message after a few seconds.  Why does this happen, and what should you do?

Basically it happens because DoCoMo has set their phones up this way:

1. They lock the SIM card.  (You can have it unlocked by them, the conditions depend on when the phone was sold).

2. The don't lock the APN (mobile access point), so if you use a DoCoMo MVNO or if you have an unlocked phone, you can set up the APN in order to get internet access.

3. They set up a setting that requires that the phone connect to a *different* APN when you use tethering.  This was mainly in order to enforce that customers pay more for tethering.  If you aren't using a DoCoMo SIM then this isn't relevant, but the phone doesn't magically lose this setting when you unlock the SIM for other carriers.

However, we can reset the setting - even without rooting the phone or reflashing the firmware or anything major like that.

We will give the instructions for Windows here, however the process should be possible on Linux or Mac OS x as well

Firstly, download the following package so that you can use the "ADB" (Android Debug) tool.

Then, turn on USB Debug in the developer options

(If the developer options screen doesn't show for you, then click the build number, found under device information,  7 times).

When you attach your device to a PC for the first time, it will ask for confirmation that the PC be authorized for debugging.  Approve this and select "OK".

Next, search for the ADB USB Debugging drivers for your model, and download from the manufacturer's site.

(For Example, Sony's drivers can be found here: http://developer.sonymobile.com/downloads/drivers/ )

Extract the files and install them.  This may involve a normal installer EE or MSI file, or may involve simply right-clicking an INF file.

Then type "ADB Shell".  If this works correctly, you will get a new line which says something like:

shell@SO-03H:/$

(Where SO-03H is the model number of your phone).

settings put global tether_dun_required 0

Then type "Exit", and turn off the USB debug option in the developer menu.  (Some applications will refuse to run when this option is enabled).

Note: We have verified that this works with the following models:

Even better, we have verified that performing software updates via the Sony PC Companion program does not seem to reset this flag.  (i.e. WiFi tethering still works after updates).

Also verified that the DoCoMo version of the Samsung Note Edge does not have this issue.  (i.e. the tethering works with DoCoMo MVNOs out of the box with no changes).