How To Install Windows 10 on a Locked T-Mobile Lumia 435

Background

So, I was on eBay one day when I found this guy selling Lumia 435s for $18(!!). So, after checking to make sure that the Lumia 435 is on the official Windows 10 upgrade list, I bought one and tried to update it to Windows 10.

Just Checking For Updates

So, I fire up my new 435 and check for updates:

Nothing, even though it should upgrade to Windows 10. Odd

Upgrade “Assistant”

After some googling I found out you need to install an app to enable the update. OK then. I saw it had a two star rating from people who were mad they couldn’t upgrade. I though I was OK though, since my phone is officially supported by Microsoft!

Burned by M$FT

Windows Insider Program

I tried the Windows Insider program to get Windows 10 too.

Unfortunantly the insider app would pop up this error message:

Server Error

A connection error prevented us from downloading programs for you. Please check the date/time of your device and its network connection and try again.

[OK]

Seems like there is some SSL cert issue going on with that app. If I set it the phone’s date to 2015, the halcyon years of Windows Phone, it would connect, but report no builds available.

Would I be stuck in the forgotten Windows Phone 8.1 wasteland? Would I be out $18?

The not-so-official way: hikari_calyx

I searched for too long for a way to force a T-Mobile Lumia 435 to upgrade to Windows 10 and found nothing, since it seems most tech-savvy people bought the unlocked version. Eventually, by accident, I was linked to a post by one hikari_calyx on XDA developers that purports to support the 435. Go there and to read their instructions, but for archival purposes I’ll reproduce the relevant portions here.

Note that hikari_calyx reccomend against using this on the 435 since the “Upgrade Assistant” supports it, but since T-Mobile blocks the update this will work just fine.

#include <std_disclaimer.h>

/*
 * Your warranty is now void.
 *
 * We are not responsible for bricked devices, dead SD cards,
 * thermonuclear war, or you getting fired because the alarm app failed. Please
 * do some research if you have any concerns about features included in this ROM
 * before flashing it! YOU are choosing to make these modifications, and if
 * you point the finger at us for messing up your device, we will laugh at you.
 *
 */

ALL CREDIT GOES TO hikari_calyx

1. This procedure might wipe your phone, so copy your crap off. For best results factory reset it before starting. At least remove your PIN though.

2. Install the Windows Device Recovery Tool

   This will help you get back to stock should anything go awry. Might have good drivers too

3. Open the W10M_Offline_Update_V4.1.txt file linked to the post above, and open the MEGA url and start the the massive 1.6 gb download of win10_mobile_offline_updater_v41.wim. since it takes about two hours

   Here is a link to the text file for archival purposes: W10M_Offline_Update_V4.1.txt. I won’t re-host the .wim here, but if the MEGA link dies @ me on Twitter and I’ll send you a new link. I hate dead links.

4. Since you have an up-to-date T-Mobile Lumia 435, your device is running version 8.10.15148.160, which is above the minimum of 8.10.14219.341 specified by hikari_calyx.

   They give the following matrix for what folder to extract:

   Lumia 52X, 62X, 720/T, 810, 820, 822, HUAWEI W2: 2nd Generation\480x800
   Lumia 1320: 2nd Generation\720x1280
   Lumia 920/T, 925/T, 928, 1020: 2nd Generation\768x1280
   Lumia 1520: 2nd Generation\1520
   Lumia 43X/532: 3rd Generation\43X-532
   Lumia 535: 3rd Generation\535
   Lumia 63X: 3rd Generation\63X
   Lumia 73X: 3rd Generation\73X
   Lumia 830: 3rd Generation\830

   So extract 3rd Generation\43X-532 somewhere convenient on your hard drive.

5. Download and extract iutool.7z from the post linked above.
   XDA link
   Mirror
6. Connect your phone
7. Open Devices and Printers on your computer (Control Panel) and uninstall your Windows Phone
8. Open an administrator command window in the folder where you extracted iutool
9. Run iutool -l and verify your phone is listed
10. Now comes the fun part - run iutool -V -p path-to-43X-532-folder-you-extracted
11. Eventually it will finish with the following message

    [1] Transferred file 134/137
    [1] Transferred file 135/137
    [1] Transferred file 136/137
    [1] Transferred file 137/137
    [1] Transferring files complete: 137 files
    [1] Update started
    [1] Unlock the device
    [1] Device unlocked
    

    I did this once and it gave me an error at the end, but it still worked. If you check the update screen in the settings app you’ll see it’s started an update

1. Wait like an hour for it to update. You’ll see the gears screen

Then some more loading screens, until you are finally running Windows 10 Mobile version 1511! The nice thing is that since the Lumia 435 (but not the T-Mobile) is officially supported, you don’t have to use any of the steps to manually copy update cab files that are detailed in the XDA post, just let it update normally and you’ll be good to go. It’ll reboot like three or so times, but eventually you’ll make it to version 1607.

It runs quite well, I’m impressed what this little thing can do.