[Radio] Enable LTE Band 3 and 8 on D820 and LTE Band 2 and 4 on D821

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Guiper

Senior Member
Sep 9, 2008
160
192
Hi,

Credits to the user Azlun who initially posted the solution on the gfan foruns (In chinese).
I'm just creating a thread here in xda to raise attention for more developers and other people which might be interested.

Azlun managed to enable some extra bands in the Nexus 5 phones. Since a lot of people import the phones, relocate or travel, this can be useful for people.

I'm not responsible if you burn your phone or make a brick from it. It has been confirmed to work for a couple of users without any downsides.

Before making any changes, please make sure you do an EFS Backup (preferentially using TWRP) as well as a backup of your original NV in a qcn format details using the QPST software download tool (instructions bellow).
This hack will be maintained even if you flash any roms or OTAs, unless you restore your EFS partition from a backup or the original qcn via the QPST software download tool.

User Xtachix put together the basis for this tutorial! Thanks! (Still under development)
Prerequisites:

First thing is first, you will need to download the file available (Will update later today).


Walkthrough/guide for adding Band 3 and 8 to D820 and 2 and 4 to the D821. Make sure you select the correct file.
Don't cross flash, as we don't know what might happen!

  • Preparation Windows
    • Install the LG Diag Drivers executing the file lg_android_31010.exe
    • Install the QPST tool, QPST_2.7.411
    • QXDM is optional and used to debug / confirm the mod has been done.
  • Preparation Nexus 5
    • Install the app Nexus 5 Field Test mode
    • Make sure you have the phone rooted
    • Enable usb debugging
    • Now you need to obtain your SPC code. For doing it open Nexus 5 Field Test Mode App, got to settings (view), then LTE, and click on edit. At the same time use logcat to get the SPC code
      Code:
      adb shell
      logcat -d | grep "commandId\ 200"
      You should get something like
      D/LG_SVC_ITEMS(18638): getCommands commandId 200 = ******-END
      Where the "*" values are the digits to your SPC.
      NOTE YOUR SPC CODE DOWN!!
    • Now let's make sure that your NV becomes writable, go back into the Field Test Application, input the SPC code from above, and make sure the settings look like the picture bellow. Important is to disable band 26 and set priority of 41 to 0. (Don't worry band 26 will become available again after flashing the qcn).
      QQ%E6%88%AA%E5%9B%BE20141026112603.png
    • After setting it, click back and your phone will reboot. This is expected
    • Make sure the kernel you are using supports DIAG mode. If you are not sure, reboot your phone into bootloader mode and boot using fastboot this kernel (even though it says 4.4.2, it will work for 4.4.4).
      Code:
      fastboot boot 4.4.2_diag_BOOT.img
    • Reboot phone into the ROM and keep it connected to the computer.
  • Executing the hack
    • Now you have to use ADB through a pc, to get you phone into DIAG mode
      Code:
      adb shell
      su
      setprop sys.usb.config diag,adb
      your device will disconnect and reconnect to become a COM port device. that's what you want.
    • Open device manager and check the COM port of the nexus, note it down.
    • Open your recently installed QPST software in windows. Windows 7/8/8.1 make sure you execute it as admin!
    • Select the ports tab and add a new port. the COM port that you noted down is what you want to select on this window. Click ok.
    • Now you will be back at the "ports" tab with your nexus 5 COM port. Up in the menus select "Start Clients" and select Software Download.
    • To be safe let's do a backup. Select the backup tab and perform a backup of your initial NV status to any file in a safe location on your computer. It may take around 5 minutes to perform the full backup.
    • Select the Restore tab.
      Now select the correct QCN file, attached on this post.
      • D820_RF_LTE_ENABLE_B3_B8_RemovedSameItem_NOT_Overrided.qcn - Adds LTE band 3 and 8 to the D820. (Band 8 not tested, let us know if it works)
      • D821_RF_LTE_ENABLE_B2_B4_Filtered_RemovedSameItem_NOT Overrided.qcn- Adds LTE bands 2 and 4 to the D821. (Band 4 not tested, let us know if it works). File updated due to a minor typo.
      for your SPC code, use what you have obtained above.
      Allow phone/file ESN mismatch" has to be ticked.
    • Click Start. After a few seconds you will see and Error .
      Errors: Could not Reset the Phone. Communication Errors Occurred. Do not panic, this means you did everything correctly :)
    • Reboot your phone.

    You should the extra bands working. Let us know if works, since we are still experimenting. We are specially looking for feedback on bands 4 for the D821 and band 8 for D820.

    There is no easy way to confirm if the new bands are working or not without connecting to them.
    Using QXDM tool you can confirm the mod has been applied, but if you are not in an area with LTE you cannot confirm it works.
    Some debug steps is to make sure your Preferred Network mode is selected as "LTE (recommended)" and your SIM Card has 4G enabled.

To disable the hack, just restore the original EFS (preferentially)and/or the qcn backup.



For more details take a look at the service manuals available here. Interesting sections are 3.5 and section 5 the RF Block.

Keep in mind that we can't enable extra bands which are not available in any of the version of the phones.
Also D820 cannot work on B20 (HW is different), neither B7 (HW is not there at all).
 

Attachments

  • D820_RF_LTE_ENABLE_B3_B8_RemovedSameItem_NOT_Overrided.zip
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Last edited:

Guiper

Senior Member
Sep 9, 2008
160
192

DigitalJosee

Senior Member
Mar 1, 2013
283
107
Seems Nexus 5 have a max. number of enable LTE bands active at the same time, disabled 26 and actived 7, using fffft's method and vndnguyen's calculator.

THANK YOU GUYS!
 

meher91

Senior Member
Jan 15, 2013
110
21
Hyderabad
Seems Nexus 5 have a max. number of enable LTE bands active at the same time, disabled 26 and actived 7, using fffft's method and vndnguyen's calculator.

THANK YOU GUYS!
Hey I'm trying to do this type of Mod for the first time on my phone...So forgive me if I ask something stupid...
I have a few doubts about the steps mentioned in fffft's post:
Step 3 - Is Custom ROM really necessary for Nexus 5?
Step 6 - I cant find the USB settings menu using any of the codes mentioned...
For the moment i'm stuck here...

Can you please solve my queries & If you dont mind can you post some details about Nexus 5 specific changes to be made to the method mentioned in fffft's post
 
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M.Noury

Senior Member
Oct 19, 2007
496
125
Jeddah
Hey I'm trying to do this type of Mod for the first time on my phone...So forgive me if I ask something stupid...
I have a few doubts about the steps mentioned in fffft's post:
Step 3 - Is Custom ROM really necessary for Nexus 5?
Step 6 - I cant find the USB settings menu using any of the codes mentioned...
For the moment i'm stuck here...

Can you please solve my queries & If you dont mind can you post some details about Nexus 5 specific changes to be made to the method mentioned in fffft's post

If you want to enable LTE band 3 only, you don't need custom ROM/Kernal. You will only need Root.

Sent from my Nexus 5 using Tapatalk
 

amritpal2489

Senior Member
Oct 3, 2010
306
48
Hey I'm trying to do this type of Mod for the first time on my phone...So forgive me if I ask something stupid...
I have a few doubts about the steps mentioned in fffft's post:
Step 3 - Is Custom ROM really necessary for Nexus 5?
Step 6 - I cant find the USB settings menu using any of the codes mentioned...
For the moment i'm stuck here...

Can you please solve my queries & If you dont mind can you post some details about Nexus 5 specific changes to be made to the method mentioned in fffft's post

I am also finding a way to open USB settings menu. Can anybody help us out with that?
 

DubelBoom

Senior Member
Jan 10, 2011
1,808
312
If anyone founds a way to edit the QCN file please share with us. I want to replace the NV Items there to support the bands I need, but QCNView won't allow editing..
 
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Guiper

Senior Member
Sep 9, 2008
160
192
Hey I'm trying to do this type of Mod for the first time on my phone...So forgive me if I ask something stupid...
I have a few doubts about the steps mentioned in fffft's post:
Step 3 - Is Custom ROM really necessary for Nexus 5?
Step 6 - I cant find the USB settings menu using any of the codes mentioned...
For the moment i'm stuck here...

Can you please solve my queries & If you dont mind can you post some details about Nexus 5 specific changes to be made to the method mentioned in fffft's post

DId a minor update to the steps. Still it's not straightforward and will require some reading, but at least it's better!
 

silentdoh

Member
Jun 14, 2012
29
12
Would it be possible to use a method similar to this to enable Band 12? The new T-Mobile deployment on it is making the N6 look pretty nice, even with the giant size and price tag.
 

Azlun

Senior Member
May 9, 2013
340
217
Shenzhen
Thank you to post my Sept 20th gfan post http://bbs.gfan.com/android-7648826-1-1.html
band3 enablement here.
To edit qcn,
Who can find QRCT from Qualcomm; just use QRCT-TOOLS-NV Manager,1st Save qcn as xml and edit it in text,
Then save it with QRCT-TOOLS-NV Manager again to qcn.
For who can not find it, I have no idea.
Sent from my SM-G9006V using XDA Free mobile app
 
Last edited:

cornholio_rules

Senior Member
Dec 29, 2010
261
66
Thank you to post my gfan post band3 enablement here. To edit qcn,you need qrct-nv tools,to save qcn as xml and edit it in text,then save it with qrct again to qcn.

Sent from my SM-G9006V using XDA Free mobile app

Great job Azlun, could you make a qcn file for D821 with added 2/4 LTE bands please? :)
 

Azlun

Senior Member
May 9, 2013
340
217
Shenzhen
Qcn for D821 to enable Band 2 and band 4 for North America Opeartors

Great job Azlun, could you make a qcn file for D821 with added 2/4 LTE bands please? :)
Here attached the qcn for band2 and band4 enablement, my NEXUS5 D821 is not in hand, so not test yet.
you can just try and let us know the results.
ATTENTION:
before below steps, use TWRP to backup your EFS 6MB file can copy it to your PC safe space, also, use QPST-Software Download-Backup tab to save a qcn file for value restoring, Please note EFS 6MB is more batter than backuped qcn. both these you should do in order to further fallback when you lost your direction.
Trail 1. User QPST-Software Download-Restore Try:
Fail solution\D821_RF_LTE_B2_B4_NV8628_NV6829_Set.qcn,
Trail2. touch back key in NEXUS5 Field Test Mode-Setting-LTE-Edit-input correct SPC as POST#1 here, then NEXUS5 will give you a button to restart and checked your LTE is working or not with LTE Discovery-EARFCN-Check
I am 99% sure it will FAIL since this old method do not patch on NV24227,NV24229;
Trial3. Do Trial1,Trial2 with My recommend qcn:
recommand\D821_RF_LTE_B2_B4_Filtered_RemovedSameItem_NOT Overrided.qcn
Trial4. if Trial3 fail to make you found the LTE, Do Trial1,Trial2 with Then restart your phone using
2nd solution\D821_RF_LTE_B2_B4_Filtered_RemovedSameItem_Overrided.qcn
Trial5. if Trial4 fail to make you found the LTE, Do Trial1,Trial2 with Then restart your phone using
2nd solution\D821_RF_LTE_B2_B4_Filtered_AllItems_Overrided.qcn
NOTE: the later solution you used, the more NV Items you have been overrided, that is bringing your RF Front end go further from factory settings. each xml files inside my attachment is telling you what Items you are modifying, you can compare.
Please note that NOT all the bands can be enabled in this way, the limitation is the Hardware Radio Frequency Front End components design in the Service manual page 203.
 
Last edited:

Azlun

Senior Member
May 9, 2013
340
217
Shenzhen
So will it be possible to covert a D820 to D821 or vise versa?

Sent from my Nexus 5 using XDA Free mobile app

NO, you can not, since D821 removed band41 Radio Frequency Front End components Filters and Power Amplifier Module,
Another side, D820 removed band 7 Radio Frequency Front End components, even they both using one PCB with difference reserved space for different bands.
if you are a expert on PCB soldering, you can add it back to PCB, then use my qcn to patch it depand on your device name.

---------- Post added at 03:30 PM ---------- Previous post was at 03:24 PM ----------

Seems Nexus 5 have a max. number of enable LTE bands active at the same time, disabled 26 and actived 7, using fffft's method and vndnguyen's calculator.

THANK YOU GUYS!

band 7 is cut in Hardware in D820 according service manual PCB pictures vs D821. so only PCB soldering expert can find a solution.
document is here:
http://forum.xda-developers.com/google-nexus-5/general/service-manual-d821-t2791303
and I have some explanation in Chinese here:
http://bbs.gfan.com/android-7664034-1-1.html

---------- Post added at 03:44 PM ---------- Previous post was at 03:30 PM ----------


Please note that wiki page just only list all official documented for China, I tried to persuade the admin to update band 1 and band 3 info for China Telecom, and band 3 info for China Unicom, but fail.
THE Fact is Band 3 is widely used for national coverage over 44 cities by both Operators above in a commercial purpose.
and band1 is used by China Telecom for some area Outdoor and some shopping mall indoor coverage.
the government documents will tell you those are trial networks, but the fact is all 4G USIM cards from CT and CU is major using such network for 4G user service,
Another side, Band41 is official assigned to All China Mobile, China Telecom and China Unicom for also 1 year, but all of these operator do NOT use it for widely coverage outdoor, the most investment is from China Mobile, only some down-town new base stations or new deployment area are using band41. it is not a full coverage network, and network based Fast Return to band41 seems still have problem in current China Mobile networks. Further info, China Mobile major 4G networks is band39 for Outdoor and band40 for indoor.
 
Last edited:

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  • 138
    Hi,

    Credits to the user Azlun who initially posted the solution on the gfan foruns (In chinese).
    I'm just creating a thread here in xda to raise attention for more developers and other people which might be interested.

    Azlun managed to enable some extra bands in the Nexus 5 phones. Since a lot of people import the phones, relocate or travel, this can be useful for people.

    I'm not responsible if you burn your phone or make a brick from it. It has been confirmed to work for a couple of users without any downsides.

    Before making any changes, please make sure you do an EFS Backup (preferentially using TWRP) as well as a backup of your original NV in a qcn format details using the QPST software download tool (instructions bellow).
    This hack will be maintained even if you flash any roms or OTAs, unless you restore your EFS partition from a backup or the original qcn via the QPST software download tool.

    User Xtachix put together the basis for this tutorial! Thanks! (Still under development)
    Prerequisites:

    First thing is first, you will need to download the file available (Will update later today).


    Walkthrough/guide for adding Band 3 and 8 to D820 and 2 and 4 to the D821. Make sure you select the correct file.
    Don't cross flash, as we don't know what might happen!

    • Preparation Windows
      • Install the LG Diag Drivers executing the file lg_android_31010.exe
      • Install the QPST tool, QPST_2.7.411
      • QXDM is optional and used to debug / confirm the mod has been done.
    • Preparation Nexus 5
      • Install the app Nexus 5 Field Test mode
      • Make sure you have the phone rooted
      • Enable usb debugging
      • Now you need to obtain your SPC code. For doing it open Nexus 5 Field Test Mode App, got to settings (view), then LTE, and click on edit. At the same time use logcat to get the SPC code
        Code:
        adb shell
        logcat -d | grep "commandId\ 200"
        You should get something like
        D/LG_SVC_ITEMS(18638): getCommands commandId 200 = ******-END
        Where the "*" values are the digits to your SPC.
        NOTE YOUR SPC CODE DOWN!!
      • Now let's make sure that your NV becomes writable, go back into the Field Test Application, input the SPC code from above, and make sure the settings look like the picture bellow. Important is to disable band 26 and set priority of 41 to 0. (Don't worry band 26 will become available again after flashing the qcn).
        QQ%E6%88%AA%E5%9B%BE20141026112603.png
      • After setting it, click back and your phone will reboot. This is expected
      • Make sure the kernel you are using supports DIAG mode. If you are not sure, reboot your phone into bootloader mode and boot using fastboot this kernel (even though it says 4.4.2, it will work for 4.4.4).
        Code:
        fastboot boot 4.4.2_diag_BOOT.img
      • Reboot phone into the ROM and keep it connected to the computer.
    • Executing the hack
      • Now you have to use ADB through a pc, to get you phone into DIAG mode
        Code:
        adb shell
        su
        setprop sys.usb.config diag,adb
        your device will disconnect and reconnect to become a COM port device. that's what you want.
      • Open device manager and check the COM port of the nexus, note it down.
      • Open your recently installed QPST software in windows. Windows 7/8/8.1 make sure you execute it as admin!
      • Select the ports tab and add a new port. the COM port that you noted down is what you want to select on this window. Click ok.
      • Now you will be back at the "ports" tab with your nexus 5 COM port. Up in the menus select "Start Clients" and select Software Download.
      • To be safe let's do a backup. Select the backup tab and perform a backup of your initial NV status to any file in a safe location on your computer. It may take around 5 minutes to perform the full backup.
      • Select the Restore tab.
        Now select the correct QCN file, attached on this post.
        • D820_RF_LTE_ENABLE_B3_B8_RemovedSameItem_NOT_Overrided.qcn - Adds LTE band 3 and 8 to the D820. (Band 8 not tested, let us know if it works)
        • D821_RF_LTE_ENABLE_B2_B4_Filtered_RemovedSameItem_NOT Overrided.qcn- Adds LTE bands 2 and 4 to the D821. (Band 4 not tested, let us know if it works). File updated due to a minor typo.
        for your SPC code, use what you have obtained above.
        Allow phone/file ESN mismatch" has to be ticked.
      • Click Start. After a few seconds you will see and Error .
        Errors: Could not Reset the Phone. Communication Errors Occurred. Do not panic, this means you did everything correctly :)
      • Reboot your phone.

      You should the extra bands working. Let us know if works, since we are still experimenting. We are specially looking for feedback on bands 4 for the D821 and band 8 for D820.

      There is no easy way to confirm if the new bands are working or not without connecting to them.
      Using QXDM tool you can confirm the mod has been applied, but if you are not in an area with LTE you cannot confirm it works.
      Some debug steps is to make sure your Preferred Network mode is selected as "LTE (recommended)" and your SIM Card has 4G enabled.

    To disable the hack, just restore the original EFS (preferentially)and/or the qcn backup.



    For more details take a look at the service manuals available here. Interesting sections are 3.5 and section 5 the RF Block.

    Keep in mind that we can't enable extra bands which are not available in any of the version of the phones.
    Also D820 cannot work on B20 (HW is different), neither B7 (HW is not there at all).
    9
    Success on Android 5.1 Lollipop!

    I've successfully enabled Band 3 LTE on D820 model running Android 5.1 Lollipop. Here is my setup:

    ROM: Calaclysm 15 March version (Android 5.1)
    Kernel: Franko.kernel r72 (Android 5.1 version)
    Windows 8.1 x64
    All files downloaded from OP.

    Just followed steps in OP and all went good. I just had my Franko kernel installed so I skipped fastboot kernel install step.
    for SPC code I used Catlog app from Playstore and also Nexus 5 Field Test app from Playstore.


    Hope it helps someone :)

    Good Luck!
    6
    Alright, I will share my personal experience on how i did this on 2 Nexus 5 D820.

    FIRST IS FIRST, BACKUP BACKUP BACKUP! x10000 and keep your backup safe. Make sure you DO backup your EFS!!!

    Test subject one = Nexus 5 D820 with ROM Simple AOSP 4.4.4.
    Test subject two = Nexus 5 D820 with ROM Miui v5 4.10.10 (android 4.4.2)

    Both phones had one thing in common, multirom.

    Mind you, I'm writing this guide assuming you have Windows.


    Prerequisites:
    First thing is first, you will need to download the file available here.
    • Windows
      • Google latest usb driver found in: latest google usb driver
      • From the downloaded zip file in "Prerequisites", extract it and install:
        • adb-setup-1.1.exe
        • QPST_2.7.378
        • QXDM-3.12.714
        • lg_android_31010.exe
    • Nexus 5
      • Open the downloaded folder above and copy com.cellmapper.nexus5fieldtestmode-1 into your internal memory.
      • Install the file
      • Make sure you have the phone rooted
      • Enable usb debugging
      • Reboot your phone into bootloader mode
      • Depending upon the ROM version you're using you will have to flash using fastboot the kernel that has been provided in that folder (notice: there are 2 available, one for 4.4.4 and the other is for 4.4.2)
      • Reboot phone into the ROM and keep it connected to the computer.

    Subject ONE walkthrough/guide (4.4.4)

    Launch the Field Test application from nexus and do what the OP said.
    to get the SPC code required for what the OP specified, i installed catlog, kept the data on, opened the browser, sent the log as an attachment to my gmail and opened the log in my pc. I searched for keyword D/LG_SVC_ITEMS (As mentioned by the OP).
    NOTE YOUR SPC CODE DOWN!!
    Again, read the OP post carefully.

    Now you have to use ADB through a pc
    Code:
    adb shell
    Code:
    su
    Code:
    setprop sys.usb.config diag,adb

    do not panic, your device will disconnect and reconnect to become a COM port device. that's what you want.
    Open device manager and check the COM port of the nexus, note it down.

    Open your recently installed QPST software in windows.
    Select the ports tab and add a new port. the COM port that you noted down is what you want to select on this window. Click ok.
    Now you will be back at the "ports" tab with your nexus 5 COM port. Up in the menus select "Start Clients" and select Software Download.
    Select the Restore tab.
    Now select the QCN file (which is obtained from the earlier downloaded zip folder)
    Code:
    80XXXXXX_RF_QDART_band3 RxTx NV patch.qcn

    for your SPC code, use what you have obtained from the logs! do not make your own.
    "Allow phone/file ESN mismatch" has to be ticked.

    Click Start.

    after a few seconds you will see and Error
    Status: Memory Restore Failed!
    Errors: Could not Reset the Phone. Communication Errors Occurred.

    again, do not panic, this means you did everything correctly :)

    Reboot your phone.

    You should have LTE band 3 working from the QCN file provided in the download :)
    congrats.


    Subject TWO walkthrough/guide (4.4.2)

    I tried to follow the same steps in subject ONE but failed.
    you have two options from here on out, either upgrade to a version 4.4.4
    OR
    use multirom to your advantage.

    I used multirom and downloaded Slimkat with Slim minimal gapps, installed it as a secondary rom.
    Now the question will come to, how do i flash the special kernel. well it is very simple :) i will guide you through that.

    Download any kernel that supports 4.4.4, Simply use 7-zip to your advantage (rename the kernel you want to boot.img) drag and dump it in the downloaded kernel. it will ask you to replace, say yes replace the existing file. now copy the file to your internal memory. boot back into multirom recovery and add zip to the slimkat, select that kernel file zip you've just copied.
    Now you have a slimkat that is ready to show you some goodies :)

    Now go to "Subject ONE walkthrough/guide (4.4.4) and follow the steps there.

    Once you've done all that, you can now boot back into your main ROM and you will have LTE/4G available.
    For people who are using miui, I simply suggest you download "4G LTE Switch" from play store and enable LTE/GSM (auto)


    Let me know if i have missed anything. :D
    That should be all. best of luck to all and have fun.
    5
    A few tips and troubleshooting points to share

    I wanted to add a couple of points, which I came across along the way of implementing the guidelines in this thread.
    The usual caveat: if you brick your phone in the process, I shall not be held responsible, I have to warn you guys, this was not the most straightforward exercise I have done on my phones, and I did root a few of them.

    Now, the points:

    Problem: Both Google Chrome and Firefox have blocked the download of lg_android_31010.exe file as malicious software.

    Solution: Use this link http://answerslg.com/download-and-i...10-for-lg-android-devices/#Lg-usb-driver-3.10 and download the file LGUnitedMobileDriver_S50MAN310AP22_ML_WHQL_Ver_3.10.1.exe – it is the same as lg_android_31010.exe .

    Problem: The downloaded QPST_2.7.411 file did not want to install properly throughits setup.exe. The Visual C++ 2005 package would get confirmed as “ok”, but the QPST would throw an error.

    Solution: There is nothing wrong with the QPST package. On your Windows 7 press “Start”, and type “run cmd”. Find a path to the .msi file inside QPST folder (by using “cd..” and “cd [folder name] commands, where “cd” stands for “change directory”, greetings to MS DOS generation). Then enter the following command, which installs msi package files as admin:
    msiexec /a "QPST 2.7.411.msi"
    It will unpack the file into the Program Files (x86) folder. For me it still was not installed, so from the normal Windows environment I went into Program Files (x86) folder -> Qualcomm -> QPST folder, where it unpacked, right clicked on the .msi file and pressed „Install”. Only then did it install properly.

    Problem: When you enter into QPST interface you may see only COM1 port available for choice, your Android Device COM Port is not shown, but in Windows Device Manager you can see that COM port Android Device is shown under COM** (where ** is a number of the COM port assigned).

    Solution: Deselect The "Show Serial and USB/QC Diagnostic Ports only" on the QPST menu and the COM port of your device will appear in the list menu in QPST, just select it.

    Problem: Some of the steps, like running adb commands through cmd, fastbooting an alternative kernel for DIAG mode, installing the drivers sound confusing.

    Solution: First of all, there are several sets of drivers mentioned here, namely, LG drivers, Android drivers, ADB drivers, and QPST, and you need to install all. LG will be needed to recognise device on COM port in QPST, because QPST will communicate with the device via virtual COM port, while still connected through USB, and because backing up of your original QCN file and uploading of the alternative QCN file provided in this thread happens through QPST, you need to install QPST drivers before the procedure too, and Android and ADB will be needed for proper communication between your phone and your PC. Well, while LG and QPST cannot be avoided, the ADB and Android driver installation can be made easier and foolproofed by installing the Nexus Root Toolkit v.2.0.5, which you probably used already to root your phone in the first place. With it you can test whether the drivers have installed correctly (full driver installation guide – advanced+manual), can always check device connectivity (check devices), can call cmd utility and run your adb commands from it (advanced utilities -> Launch CMD Prompt), can even temporarily fastboot the kernel for DIAG mode, no need to download the alternative kernel separately (advanced utilities -> modified boot.img) and all this at a press of a button. So I can’t recomment the tool more for the purposes of this thread.

    Question: Is there an alternative way to back up EFS file?
    Answer: EFS yes, there is an easier way to do that, as described in this excellent guide http://forum.xda-developers.com/goo...t/modem-nexus-5-flashable-modems-efs-t2514095 (use Nexus Root Toolkit), but it does not take care of your QCN file, for QCN you still need to run QPST, as described above.

    One more question I had was whether my kernel had DIAG mode, or I needed to flash a temporary kernel, which has such capability. While you can go through a routine to check, my advice is to use fastboot to temporarily enter the system with the suitable DIAG kernel, which, as said above, easily done with the help of Nexus Root Toolkit.

    Another qestion which I had and which did not have a ready answer, is whether a temporary kernel that you are supposed to flash will stick and replace the kernel you had before. The answer is that if you use fastboot, it will load once, and on your next reboot your notmal kernel will return. Hope someone will find this clarification useful.

    That concludes my 1st attempt to give back to the excellent community at xda and the great bunch behind this and adjacent threads. Thank you guys, I did manage to unlock my Band 3 on a D820 model SlimKat 4.4.4 (tested) (yes, I rolled back from Lollipop, because I expect that another year or so will pass until the app developers will get to grips with it and adjust their apps on Google Play, and until all bugs and glitches within Lollipop itself are smoothed out to give us the seamless experience, mind you, I sat on 2.3 Gingerbread, Siyah kernel on my SGS II until now, having had this phone for 4 years, stability and reliability are king for me, yet flexibility and customization for comfortable use are a must, too). In fact, 3g is sufficient for me, as, probably, for most of us, especially given that a modem working on LTE Band 3 frequesncy in a 2m radius gives me a headache, tested on several occasions, so this was done for futureproofing, marketability and, of course, for the fun of it.
    5
    Can someone update the OP? The links are bad and one is full of malware (QPST)
    I was able to get this working on my old stock D821 Nexus5 in the USA on T-Mobile (rooted, TWRP, and ElementalX kernel). Upon reboot it started up on H but then quickly switched over to LTE.

    QPST (2.7.460) was found HERE
    LG Diag Drivers (4.2) were found HERE

    Hope this helps!