[Tutorial] Crossflash, Bypass OPID Mismatched Error

Search This thread

Khmer_Boy

Member
Apr 25, 2013
11
0
Hi there ;)
Thanks to all other guys here who have made helpful development to tame this beautiful =)

To crossflash models other than LG G8 please read post 3.
Before asking any question please read the troubleshooting section at the bottom of the page.
If you still need some specific help I would appreciate if you bring it up just in the thread instead of sending direct messages.


LG has made things difficult in flashing custom and even stock roms by this new OPID thing! It prevents us from crossflashing but we have been able to use TWRP and change the system and some other partitions to have a different rom. We had to make some changes into OP partition using HxD editor.
But now, through this tutorial, we're able to flash any rom without the need to change OPID in OP partition. Also, there is no need to root or unlock boot-loader.
I was successful to do this on some G8 (LMG820UM) but I AM NOT RESPONSIBLE FOR ANY HARM TO YOUR PHONE!

By continuing to read the following instructions you are actually accepting the risk.


IMPORTANT!
first, MAKE A FULL BACKUP OF ALL PARTITIONS; and I mean it!!!
at least, for your sake, make a backup of "modemst1, modemst2, fsg, fsc, ftm" partitions, for emergency.


Requirements
QPST and Qualcomm USB Driver (get)
LGE SM8150 Firehose (get)
LGUP 1.16.0.3 (get)
LGUP_Common.dll (get)
UI_Config.lgl (get)
LG Mobile Driver 4.4.2 (get)


Preparation
1. Install QPST and Qualcomm USB Driver.
2. Install LGUP.
3. Find the folder named "model" in the installation directory of LGUP, then Create a folder named "common" in the "model" folder.
4. Move "LGUP_Common.dll" and "UI_Config.lgl" into "common" folder. Change the attribute of "UI_Config.lgl" to read only.
5. Install LG Mobile Driver 4.4.2.


Steps
A)
1. Open QFIL.
2. Change "Storage Type" to UFS.
3. Select "Flat Build".
4. Browse for "LGE SM8150 Firehose" and pick it.
5. Now, connect the phone to PC and boot into EDL mode.
6. Open "Select Port" and select the phone, press OK.
7. In "Tools" open the "Partition Manager".

B)
!!!BE CAREFUL TO DO EXACTLY AS THE INSTRUCTIONS SAY OR YOU WILL BRICK THE PHONE!!!
1. Make a backup of and erase these 7 partitions: FTM, Modem_A, Modem_B, SID_A, SID_B, OP_A, OP_B.
1.1. You have to left-click on a partition then right-click on it and select "Manage Partition Data".
1.2. In the pop-up window, you have 4 choices: I. Erase (to erase data on the partition), II. Read Data (to dump or back up the partition), III. Load Image (to restore the partition), IV. Close (to close the window).
1.3. First dump/back up the partition by choosing "Read Data" then Erase it.
2. Close the "Partition Manager" window.
3. Wait for 5 seconds then press Vol- and Power until it restarts.
3.1. Immediately after rebooting, Release the Vol- and Power buttons and press Vol+ to get into Download Mode.
Note: Do not let the phone to begin to boot! If it begins to boot, it may regenerate the SID and FTM partitions data and so you need to redo the whole step B.

C)
1. Open LGUP.
2. Pick your favorite KDZ.
3. Select "PARTITION DL".
4. Press Start. And a pop-up window will appear. In this window you can select which partitions to be flashed.
5. Here, uncheck these partitions: SID_A and SID_B. It will make it able to bypass the OPID Mismatched Error.
6. If you are in Sprint or other platforms you will get the message whether to change the model or not. Of course you know what to do =)

after completing the process it will boot up in some minutes and before starting the customization it will do one restart. just be patient.


ERRORS, QUESTIONS, TROUBLESHOOTING
1. Can I crossflash V50, V60, G8X or other LG devices using this method?
I did it on V50. Maybe it'll work on your devices maybe won't. There's one way to find out; make backup and give it a try.
2. SN is gone, zero, etc.
Restore your original FTM.
3. I can't get into recovery.
Restore the original FTM.
4. I got NT-Code error.
It's been discussed many time in the thread and some solutions have been presented (such as this one, thanks to @animo214). However, you can ignore it if the phone got network.
5. IMEI is lost, zero, null etc.
Restore LUN5 partitions. If you have no backup it should be repaired using Octopus box. Go to 16.
6. I got "permanently locked" error.
This is because of IMPL lock and you have to restore LUN5 partitions. In case of having no backup you should use Octopus box.
7. All partitions are deleted accidentally.
Follow this instructions.
8. I need to get into PDM mode.
Unzip and restore the attached PDM to FTM partition. Remember, you need to restore your FTM to get into OS.
9. Can I use another phone's LUN5 backup?
NO.
10. Can I use another phone's FTM backup?
Yes. All partitions can be restored from another phone's backup except LUN5 partitions.
11. My phone is stuck in boot-loop.
Restore the original FTM and if it doesn't help redo the whole crossflash process and use a different KDZ this time.
12. Which KDZ is the best (for any matter of use)?
I do not know.
13. Can I crossflash from any source variant to Korean variant or vice versa?
Yes it is possible but you may get error on opening stock camera application because of hardware differences. There are some methods to solve the issue which you can search and find them. It is out of topic here.
14. Can I downgrade using this method?
Yes.
15. I erased partitions (ftm, op_a, op_b, modem_a, modem_b, sid_a, sid_b) but it still does not let me to crossflash.
Redo the whole process and this time make backup of and erase these partitions too, on both sides A and B: vendor, product, system, userdata and boot.
16. How can I write IMEI?
A) Dump the modem_a and create a copy of it. Then open it in UltraIso and remove IMEIPROT files from image folder. Save and restore it in place of modem_a and modem_b partitions.
B) Make backup of FTM and then flash or restore the PDM file (attached) into your ftm partition. Restart the phone; you'll get into PDM mode.
C) Open Tutty (attached). Select "Serial" in protocol and the proper port of your phone's modem driver. Click open. To test if you have selected the proper port number type "at" and hit enter it should respond"ok". Type the code at%imei=# (replace # with your IMEI) and hit enter. It doesn't matter you get "error" or "ok" after that, just check if IMEI is written via this code at%imei=?. If IMEI is written so you'll have the right MEID and ESN too.
D) Restore the original ftm and modem_a in place of modem_a and modem_b. Restart the phone.
I've already tested this method on V30, V50 and G8. Remember, if the phone has IMPL lock it'll throw "perm. locked" error even if you have written the IMEI.
17. I have lost GPT files of my LG G8, G8X, G8S, V50, etc. and Qfil partition manager does not show anything in the list.
You need to flash GPT files to your device with fh_loader (see this, part C). For that matter use KDZ_Tools to Extract DZ from a KDZ of your device. Then extract the DZ using -c at the end of extracting command. For example: unkdz -f FILE_NAME.kdz -c. It will extract all files besides all GPTs.
Hello! I’m pretty new to this crossflashing and I was wondering if you can help explain about Lun5 partitions? Where to extract that?
 

micallan_17

Senior Member
Sep 27, 2012
215
115
Santa Elena
quick update on the ATT Stylo 5+ i was able to flash the open firmware using a CMD version of DEV LGUP but now the device is stuck on displayinig OPID Mismatch, no way to go back to the ATT ROM since it's not available, and since no firehose for the SDM 450 on the Stylo has been found, am not sure what else i can try to get it back. will see what else i can do with it
 

nortnil

Member
Jul 8, 2010
41
9
I cross flashed from the unlocked 820QM firmware to the Verizon variant and it worked and allowed me to get wifi calling on their network, but I hated the software and flashed back to a fresh install instead of flashing from my backups. Then I messed around in the hidden menu trying to get wifi calling settings to work again.

Which partitions should I reflash to ensure all of the modem/network settings I may have changed in the hidden menu are back to stock settings?
 

arksid

Member
Sep 9, 2022
9
0
Hi, i recently flashed my lg 830um with android 11 from at&t's android 9, but now the bottom speaker doesn't work only the one under the screen works. Is there anything i did wrong or i need to add or change?
 

arksid

Member
Sep 9, 2022
9
0
Hi, i recently flashed my LG g8 thinq G820um with android 11 open_CAN version from at&t's android 9, but now the bottom speaker doesn't work only the one under the screen works. Is there anything i did wrong or i need to add or change. The speaker was working before when the phone had AT&Ts android 9. I also tried using android 9 and 10 but none works.
 

RigobertoEHA1

New member
Nov 5, 2022
2
0
brothers, can help me i have this phone
model: LMV450PM region: SPR

when i try to install "V500EM40b_00_OPEN_EEA_OP_0517.kdz" i have this error:

Error: 0x6004, CrossDL flashlm_lao_com>@flashlmdd Target_productchanged.

but its done if i try this "V450VM40a_00_VZW_US_OP_0524.kdz"

i dont want this system of verizion, i need the global kdz please
 

garyww39

Senior Member
Sep 10, 2021
81
9
LG K31 Crossflashing:
To crossflash LG K31 go to this guide. Thanks to @Wish39.

LG Stylo 6 Crossflashing:
To crossflash LG Stylo 6 using LG K71 Android 12 firmware see this. Thanks to @Wish39.

LG V50 Crossflashing:
I had two LG V50 (LMV450) to which I flashed Korean Andorid 12 using the method mentioned in the first post. I cannot guarantee that it will work on every V50. After corssflashing I found out that one of them had the problem of draining battery due to not getting into deep sleep mode. To overcome the issue, I reflashed it via "Chip Erase" this time, and then again reflashed it but in the same way mentioned for crossflashing in the first post. Of course, I had created backup and at the end I restored LUN5 partitions.
hi im trying your tutorial on my g8x when i open qfil only time i see storage option is when meta build is selected and even then i cant change the build if i switch it to flat build the storage selection disappears
 
Last edited:

garyww39

Senior Member
Sep 10, 2021
81
9
hi im trying your tutorial on my g8xwhen i open qfil only time i see storage option is when meta build is selected and even then i cant change the build if i switch it to flat build the storage selection disappears
i also have a lg g8x demo board it powers up and displays a android operating system but i was told it cant be used with any cell service but not sure if it can be messed with or its just trash also was told on the demo version the 128gb storage is not true its much smaller
 

bexiu

Member
Mar 14, 2018
28
4
I follow your way dowgrade my lg g8 thinkQ G G820UM20S to it's original android 9 pie, but at step C, I forgot check SID_A, SID_B, got error OPID mismatch, I redo again step B, erease but when enter download mode, nothing show info of phone, only text "download mode". Now, LGUP also can't read mode & port. What should I do? thanks bro
 

Attachments

  • unnamed.png
    unnamed.png
    154.1 KB · Views: 33

netmsm

Senior Member
Oct 3, 2010
514
215
Esfahan
LG V30
I follow your way dowgrade my lg g8 thinkQ G G820UM20S to it's original android 9 pie, but at step C, I forgot check SID_A, SID_B, got error OPID mismatch, I redo again step B, erease but when enter download mode, nothing show info of phone, only text "download mode". Now, LGUP also can't read mode & port. What should I do? thanks bro
That's weird !_!
Are you sure "laf_a" and "laf_b" partitions are intact? Try to restore them.
For the second attempt, restore your backups of other partitions.
 

bexiu

Member
Mar 14, 2018
28
4
Are you sure "laf_a" and "laf_b" partitions are intact? Try to restore them.
For the second attempt, restore your backups of other partitions.
I saved
[ fsc_backup.bin
fsg_backup.bin
ftm_backup.bin
misc.bin
modemst1_backup.bin
modemst2_backup.bin
modem_A
modem_B
"SID_A,SID_B"
OP_A
OP_B ]
but not save "laf_a" and "laf_b"
 
Last edited:

kt-Froggy

Senior Member
Sep 14, 2012
1,708
749
YVR
LG G8
Samsung Galaxy S10e
First off, big THANKS to the OP (netmsm) and other people who contributed to this thread and made this guide very clear and useful!

So, after perusing this thread for a long time, trying to understand the ins and outs of the process and any possible snafus, I decided to take the plunge after the Open_CA A12 (40a) got released recently, and to flash it onto my G8 originally from US Cellular. The crossflash went smoothly with no issues at all. A nice surprise was that the BL remained unlocked - I was prepared to go through the whole unlocking process again before rooting, but didn't have to. I got the empty S/N (easy fix), and the infamous NT-Code error. This is where I got stuck for a while. I tried fixing it by editing the cust_path_mapping.cfg file as suggested in the thread. The problem is that I couldn't save the changes in that stupid file by using ANY root explorer/editor! :mad: Tried half a dozen different apps with no luck at all. BTW, anyone has any ideas what I may have been doing wrong?? Yes, I am properly rooted with Magisk.

Anyway... Everything worked fine on the phone, but that lame error was really getting under my skin - I could have ignored it, but I hated not being able to get rid of it. So... After more reading, I came across some info on hex-editing the FTM partition (in a totally unrelated topic). The NT-Code in FTM binary is stored at the offset 00014000. My error message was referring to the code "FFFFFF,85". The original cust_path_mapping.cfg file (which I couldn't edit) had a line referring to "FFFFFF,82". So, having all backups available, I decided, just for the heck of it, to change the last digits of the NT-Code in the FTM partition to match the "82" listed in the file. What could go wrong? I can always restore a backup... After flashing the edited FTM in QFIL, rebooted the phone, and - bingo! The NT-Code error was gone, and the phone was still fully functional. This was my happy face after spending a good hour and a half trying to get rid of it, and finally succeeding: 😁

Cheers, and thanks again for all the info!
 

tofik33`

Member
Jun 19, 2022
20
4
Anyway... Everything worked fine on the phone, but that lame error was really getting under my skin - I could have ignored it, but I hated not being able to get rid of it. So... After more reading, I came across some info on hex-editing the FTM partition (in a totally unrelated topic). The NT-Code in FTM binary is stored at the offset 00014000. My error message was referring to the code "FFFFFF,85". The original cust_path_mapping.cfg file (which I couldn't edit) had a line referring to "FFFFFF,82". So, having all backups available, I decided, just for the heck of it, to change the last digits of the NT-Code in the FTM partition to match the "82" listed in the file. What could go wrong? I can always restore a backup... After flashing the edited FTM in QFIL, rebooted the phone, and - bingo! The NT-Code error was gone, and the phone was still fully functional. This was my happy face after spending a good hour and a half trying to get rid of it, and finally succeeding: 😁
Hi. Can you please send a link to the tutorial how to edit the FTM partition?
 

kt-Froggy

Senior Member
Sep 14, 2012
1,708
749
YVR
LG G8
Samsung Galaxy S10e
Hi. Can you please send a link to the tutorial how to edit the FTM partition?
This is the thread I found: https://forum.xda-developers.com/t/getting-access-to-recovery-combination-ftm-mod.4220523/

Note that these steps were described for a different phone and a different issue, and CAN'T be blindly applied here! It just gave me an idea of what could possibly be done. I know nothing about this other than what's described there, and won't be able to answer any questions if things get messed up. Please use this info at your own risk. And have a backup. And a backup of a backup, just in case.
 
Last edited:
  • Like
Reactions: ufocus and tofik33`

tofik33`

Member
Jun 19, 2022
20
4
This is the thread I found: https://forum.xda-developers.com/t/getting-access-to-recovery-combination-ftm-mod.4220523/

Note that these steps were described for a different phone and a different issue, and CAN'T be blindly applied here! It just gave me an idea of what could possibly be done. I know nothing about this other than what's described there, and won't be able to answer any questions if things get messed up. Please use this info at your own risk. And have a backup. And a backup of a backup, just in case.
Unfortunately it doesn't work for me. When I load the edited FTM the NT-code no longer exists but my phone cannot connect to cellular network. Any ideas?
 

Top Liked Posts

  • There are no posts matching your filters.
  • 46
    Hi there ;)
    Thanks to all other guys here who have made helpful development to tame this beautiful =)

    To crossflash models other than LG G8 please read post 3.
    Before asking any question please read the troubleshooting section at the bottom of the page.
    If you still need some specific help I would appreciate if you bring it up just in the thread instead of sending direct messages.


    LG has made things difficult in flashing custom and even stock roms by this new OPID thing! It prevents us from crossflashing but we have been able to use TWRP and change the system and some other partitions to have a different rom. We had to make some changes into OP partition using HxD editor.
    But now, through this tutorial, we're able to flash any rom without the need to change OPID in OP partition. Also, there is no need to root or unlock boot-loader.
    I was successful to do this on some G8 (LMG820UM) but I AM NOT RESPONSIBLE FOR ANY HARM TO YOUR PHONE!

    By continuing to read the following instructions you are actually accepting the risk.


    IMPORTANT!
    first, MAKE A FULL BACKUP OF ALL PARTITIONS; and I mean it!!!
    at least, for your sake, make a backup of "modemst1, modemst2, fsg, fsc, ftm" partitions, for emergency.


    Requirements
    QPST and Qualcomm USB Driver (get)
    LGE SM8150 Firehose (get)
    LGUP 1.16.0.3 (get)
    LGUP_Common.dll (get)
    UI_Config.lgl (get)
    LG Mobile Driver 4.4.2 (get)


    Preparation
    1. Install QPST and Qualcomm USB Driver.
    2. Install LGUP.
    3. Find the folder named "model" in the installation directory of LGUP, then Create a folder named "common" in the "model" folder.
    4. Move "LGUP_Common.dll" and "UI_Config.lgl" into "common" folder. Change the attribute of "UI_Config.lgl" to read only.
    5. Install LG Mobile Driver 4.4.2.


    Steps
    A)
    1. Open QFIL.
    2. Change "Storage Type" to UFS.
    3. Select "Flat Build".
    4. Browse for "LGE SM8150 Firehose" and pick it.
    5. Now, connect the phone to PC and boot into EDL mode.
    6. Open "Select Port" and select the phone, press OK.
    7. In "Tools" open the "Partition Manager".

    B)
    !!!BE CAREFUL TO DO EXACTLY AS THE INSTRUCTIONS SAY OR YOU WILL BRICK THE PHONE!!!
    1. Make a backup of and erase these 7 partitions: FTM, Modem_A, Modem_B, SID_A, SID_B, OP_A, OP_B.
    1.1. You have to left-click on a partition then right-click on it and select "Manage Partition Data".
    1.2. In the pop-up window, you have 4 choices: I. Erase (to erase data on the partition), II. Read Data (to dump or back up the partition), III. Load Image (to restore the partition), IV. Close (to close the window).
    1.3. First dump/back up the partition by choosing "Read Data" then Erase it.
    2. Close the "Partition Manager" window.
    3. Wait for 5 seconds then press Vol- and Power until it restarts.
    3.1. Immediately after rebooting, Release the Vol- and Power buttons and press Vol+ to get into Download Mode.
    Note: Do not let the phone to begin to boot! If it begins to boot, it may regenerate the SID and FTM partitions data and so you need to redo the whole step B.

    C)
    1. Open LGUP.
    2. Pick your favorite KDZ.
    3. Select "PARTITION DL".
    4. Press Start. And a pop-up window will appear. In this window you can select which partitions to be flashed.
    5. Here, uncheck these partitions: SID_A and SID_B. It will make it able to bypass the OPID Mismatched Error.
    6. If you are in Sprint or other platforms you will get the message whether to change the model or not. Of course you know what to do =)

    after completing the process it will boot up in some minutes and before starting the customization it will do one restart. just be patient.


    ERRORS, QUESTIONS, TROUBLESHOOTING
    1. Can I crossflash V50, V60, G8X or other LG devices using this method?
    I did it on V50. Maybe it'll work on your devices maybe won't. There's one way to find out; make backup and give it a try.
    2. SN is gone, zero, etc.
    Restore your original FTM.
    3. I can't get into recovery.
    Restore the original FTM.
    4. I got NT-Code error.
    It's been discussed many times in the thread and some solutions have been presented (such as this one, thanks to @animo214 and this, thanks to @kt-Froggy as well as this one, thanks to @StvOchi ). However, you can ignore it if the phone got network.
    Note: You need to disable verity on the phone in advance otherwise changes in cust_path_mapping.cfg won't be saved.
    5. IMEI is lost, zero, null etc.
    Restore LUN5 partitions. If you have no backup it should be repaired using Octopus box. Go to 16.
    6. I got "permanently locked" error.
    This is because of IMPL lock and you have to restore LUN5 partitions. In case of having no backup you should use Octopus box.
    7. All partitions are deleted accidentally.
    Follow this instructions.
    8. I need to get into PDM mode.
    Unzip and restore the attached PDM to FTM partition. Remember, you need to restore your FTM to get into OS.
    9. Can I use another phone's LUN5 backup?
    NO.
    10. Can I use another phone's FTM backup?
    Yes. All partitions can be restored from another phone's backup except LUN5 partitions.
    11. My phone is stuck in boot-loop.
    Restore the original FTM and if it doesn't help redo the whole crossflash process and use a different KDZ this time.
    12. Which KDZ is the best (for any matter of use)?
    I do not know.
    13. Can I crossflash from any source variant to Korean variant or vice versa?
    Yes it is possible but you may get error on opening stock camera application because of hardware differences. There are some methods to solve the issue which you can search and find them.
    14. Can I downgrade using this method?
    Yes.
    15. I erased partitions (ftm, op_a, op_b, modem_a, modem_b, sid_a, sid_b) but it still does not let me to crossflash.
    Redo the whole process and this time make backup of and erase these partitions too, on both sides A and B: vendor, product, system, boot and userdata. Do not make backup of userdata partition.
    16. How can I write IMEI?
    A) Dump modem_a and create a copy of it. Then open it in UltraISO and remove IMEIPROT files from image folder. Save and restore it in place of modem_a and modem_b partitions.
    B) Make backup of FTM and then flash or restore the PDM file (attached) into your ftm partition. Restart the phone; you'll get into PDM mode.
    C) Open Tutty (attached). Select "Serial" in protocol and the proper port of your phone's modem driver. Click open. To test if you have selected the proper port number type "at" and hit enter it should respond"ok". Type the code at%imei=# (replace # with your IMEI) and hit enter. It doesn't matter you get "error" or "ok" after that, just check if IMEI is written via this code at%imei=?. If IMEI is written so you'll have the right MEID and ESN too.
    D) Restore the original ftm and modem_a in place of modem_a and modem_b. Restart the phone.
    I've already tested this method on V30, V50 and G8. Remember, if the phone has IMPL lock it'll throw "perm. locked" error even if you have written the IMEI.
    17. I have lost GPT files of my LG G8, G8X, G8S, V50, etc. and Qfil partition manager does not show anything in the list.
    You need to flash GPT files to your device with fh_loader (see this, part C). For that matter use KDZ_Tools to Extract DZ from a KDZ of your device. Then extract the DZ using -c at the end of extracting command. For example: unkdz -f FILE_NAME.kdz -c. It will extract all files besides all GPTs.
    18. Which are the LUN5 partitions?
    SM8150 has 7 physical partitions known as LUNs which are numbered from 0 to 6. Each LUN is split into several partitions. In Qfil Partition Manager you can see all partitions except those of LUN3 and LUN6 which are hidden. The number of LUNs are shown under the first column named LUN. Therefore, all partitions in front of number 5 are LUN5 partitions.
    5
    Hey good for you, so the Open a11 must be the Kor version right? Either way, could u do a big favor and try to get to recovery? Of course don't erase anything, but just verify you can get to the recovery screen?

    thnx!

    So, we just got this sorted. Thanks to SGMarkus as he mentioned it's the ftm partition that controls recovery access and fastboot access. So, with the newly flashed kdz, as it is, you can't even get to fasboot although u flashed the eng abl to it.

    But! Restore your old ftm, after flashing, and then you'll get access to both recovery and ability to get to fastboot after flashing eng abl.

    cheers!
    4
    alright, G8x Sprint succesfully crossflashed to OPEN CA :cowboy:
    4
    First off, big THANKS to the OP (netmsm) and other people who contributed to this thread and made this guide very clear and useful!

    So, after perusing this thread for a long time, trying to understand the ins and outs of the process and any possible snafus, I decided to take the plunge after the Open_CA A12 (40a) got released recently, and to flash it onto my G8 originally from US Cellular. The crossflash went smoothly with no issues at all. A nice surprise was that the BL remained unlocked - I was prepared to go through the whole unlocking process again before rooting, but didn't have to. I got the empty S/N (easy fix), and the infamous NT-Code error. This is where I got stuck for a while. I tried fixing it by editing the cust_path_mapping.cfg file as suggested in the thread. The problem is that I couldn't save the changes in that stupid file by using ANY root explorer/editor! :mad: Tried half a dozen different apps with no luck at all. BTW, anyone has any ideas what I may have been doing wrong?? Yes, I am properly rooted with Magisk.

    Anyway... Everything worked fine on the phone, but that lame error was really getting under my skin - I could have ignored it, but I hated not being able to get rid of it. So... After more reading, I came across some info on hex-editing the FTM partition (in a totally unrelated topic). The NT-Code in FTM binary is stored at the offset 00014000. My error message was referring to the code "FFFFFF,85". The original cust_path_mapping.cfg file (which I couldn't edit) had a line referring to "FFFFFF,82". So, having all backups available, I decided, just for the heck of it, to change the last digits of the NT-Code in the FTM partition to match the "82" listed in the file. What could go wrong? I can always restore a backup... After flashing the edited FTM in QFIL, rebooted the phone, and - bingo! The NT-Code error was gone, and the phone was still fully functional. This was my happy face after spending a good hour and a half trying to get rid of it, and finally succeeding: 😁

    Cheers, and thanks again for all the info!
    Thanks, netmsm and kt-froggy for the guides.
    I figured out how to remove the NT code error without root.
    You will first need a file manager that can access the root directory.
    I personally used "Solid Explorer File Manager" to access the cust_path_mapping.cfg file to read the NT-Code that came with the firmware.
    You can use the Solid Explorer File Manager to access the root directory by going to settings then scrolling down and checking the box "show root storage". You will now be able to access the root storage.
    You can access the cust_path_mapping.cfg by going to root/system/product/OP. Then open the file and note the code. Mine was FFFFFF,82=/product/OP.
    Create a backup of the FTM partition the open the FTM file with HxD app. (Make sure you have a copy of the FTM file in case something goes wrong)
    Go to line 00014000 and edit the line. depending on the phone, edit the first 2 sets of numbers/letters with 3 characters separated by a comma. ("FFF,FFF), then the last set of numbers/letters with 2 characters to match the code in the cust_path_mapping.cfg file.
    (Mine was
    "2","310,120,FFFFFFFF,FFFFFFFF,FF","312,530,FFFFFFFF,FFFFFFFF,FF" and I changed to
    "2","FFF,FFF,FFFFFFFF,FFFFFFFF,82","FFF,FFF,FFFFFFFF,FFFFFFFF,82") because I was getting NT code error
    310120, 312530 ; FF, FF

    Note:
    1. The line could span from 00014000 to 00014040 like mine. Each line is separated with "". I had 2 lines and had to change both lines. You can have only 1 line
    2. Make sure you don't delete the line but just select the content and overwrite it with new text. deleting might affect other lines below with content. ( I deleted some lines and my phone factory reset)


    After that just save the FTM and load it to your phone using QFIL and the error will be gone.

    I've only tested it on my LG G8, OPEN CA firmware so I'm not sure if it will work on others.
    4
    First off, big THANKS to the OP (netmsm) and other people who contributed to this thread and made this guide very clear and useful!

    So, after perusing this thread for a long time, trying to understand the ins and outs of the process and any possible snafus, I decided to take the plunge after the Open_CA A12 (40a) got released recently, and to flash it onto my G8 originally from US Cellular. The crossflash went smoothly with no issues at all. A nice surprise was that the BL remained unlocked - I was prepared to go through the whole unlocking process again before rooting, but didn't have to. I got the empty S/N (easy fix), and the infamous NT-Code error. This is where I got stuck for a while. I tried fixing it by editing the cust_path_mapping.cfg file as suggested in the thread. The problem is that I couldn't save the changes in that stupid file by using ANY root explorer/editor! :mad: Tried half a dozen different apps with no luck at all. BTW, anyone has any ideas what I may have been doing wrong?? Yes, I am properly rooted with Magisk.

    Anyway... Everything worked fine on the phone, but that lame error was really getting under my skin - I could have ignored it, but I hated not being able to get rid of it. So... After more reading, I came across some info on hex-editing the FTM partition (in a totally unrelated topic). The NT-Code in FTM binary is stored at the offset 00014000. My error message was referring to the code "FFFFFF,85". The original cust_path_mapping.cfg file (which I couldn't edit) had a line referring to "FFFFFF,82". So, having all backups available, I decided, just for the heck of it, to change the last digits of the NT-Code in the FTM partition to match the "82" listed in the file. What could go wrong? I can always restore a backup... After flashing the edited FTM in QFIL, rebooted the phone, and - bingo! The NT-Code error was gone, and the phone was still fully functional. This was my happy face after spending a good hour and a half trying to get rid of it, and finally succeeding: 😁

    Cheers, and thanks again for all the info!