Steps to get the Fingerprint working with unlocked bootloader and Root

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gd243

Member
Sep 18, 2021
22
11
Any chance this method would work on an LG Wing? I was directed here through some other posts. Fingerprint scanner wouldn't do anything at first, and after this it would recognize the finger but just say to put the entire finger on the screen. Can't install android 9 because it didn't ship with that, but I did everything else.
 

Marciniuk

New member
Oct 4, 2021
4
1
Can dm-verity block fingerprint scaner? I wonder what is the reason for the blockade and what is responsible for it. If this question is stupid forgive me, I don't know the structure of an android
 

nsublis

New member
Sep 30, 2020
3
2
About the newer test in Android 10:

I am on Linux, and so I cannot use LGUP to downgrade. It would seem that the new service menu only gives you the option to enable the fingerprint sensor if you actually manage to pass the tests, which appears to be harder than on the older version. There are a few automatic tests first, which should all pass, but then there are three manual tests: WBOX, BBOX, and CHARTER. I believe that the meanings of these three tests are White Box, Black Box, and perhaps some sort of special calibration pattern. It appears it's not too hard to pass WBOX and BBOX by just finding approximately-fingerprint-sized white and black objects (in my case, my white pasty thumb works well enough for WBOX), then placing them on the green part of the screen and starting the respective tests, but I have no idea what sort of calibration pattern might be used for CHARTER. If anyone has any ideas or manages to get the Android 10 test to work, I would love to hear about it.

EDIT: Also, if anyone knows how to extract the service menu APK from the Android 9 KDZ, that would be greatly appreciated, as it may allow installing and using the older service menu without the OS downgrade.
 
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nsublis

New member
Sep 30, 2020
3
2
As an update, some reverse-engineering shows that the tests are actually irrelevant in the new service menu; it doesn't seem to contain any code at all for re-enabling the fingerprint reader, just for the tests themselves, so that's a bit of a dead end. I tried to extract the old hidden menu APK from a KDZ, but most of the partitions wouldn't mount (via SALT) and I think it was on one of those.
 
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jian1

Senior Member
Apr 14, 2014
53
1
Working with LG G8X after flashing with LGUP the G850UM10g firmware (Android 9 Canadian). Automatic OTA upgrade to Android 10 (G850UM10j) is also automatically downloaded over Wifi. Merci! Thank you!
Where did you download the g850um10g firmwares? All I found is 20 firmwares (android 10)Thanks
 
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jian1

Senior Member
Apr 14, 2014
53
1
big trouble!!! with bootloader unlocked, screen locked and rooted 20J when using LGUP to flash back to 10g, it prompts for some password screen and gave me 16 tries.... I think I am in big trouble, what should I next?

ETA: nvm, it seems that you CANNOT upgrade BACK to 10g, only a refurbish(wipe) downgrade is allowed... otherwise the phone will keep prompting you for some passwords
 
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ranenshio

Member
Jul 15, 2022
7
1
Make sure you have backed up your 20e stock abl.

You will need to download the Android 9 kdz "G850EMW10c_00_1126.kdz"
link to Android 9 kdz:

If you are already on stock with locked bootloader, then start with step 5

Step 1: backup all parittions using qfil
Step 2: flash 20e kdz file using LGUP to get back to stock.
Step 3: flash engg abl in qfil
Step 4: go to fastboot and lock the bootloader.
Step 5: flash 10c (Android 9) using LGUP to go to Android 9
Step 6: Since you are on locked bootloader and Android now, FP works.
Step 7: Register pin and password and select secure pin to boot.
Step 8: Now reboot and enter incorrect pin for 30 times . this will reset ur device again (this is damn time taking)
Step 9: Now flash 20e kdz file using LGUP to get back to stock Android 10. (don'r register fp)
Step 10: flash engg abl in qfil
Step 11: go to fastboot and unlock the bootloader.
Step 12: flash 10c (Android 9) using LGUP to go to Android 9
Step 13: Now you are on unlocked Bootloader and Android 9
Step 14: Now try registering, it might fail.
Step 15: go to User Service menu -> Device test -> SAAT -> Service Menu -Manual Test - Optical Fingerprint test (test it few times)
Step 16: go to User Service menu -> SVC -> Enable FacePrint and Enable Handprint
Step 17: Try registering finger print in settings, it should work. If it doesn'r reboot and do the step 15 and 16 and try again.
Step 18: You must get the fingerprint working in Unlocked Android 9, that's the key
Step 19: It will work after some 1-2 times of step 15 and 16
Step 20: Register your finger print in unlocked Android 9. FInish the scan and set it up.
Step 21: flash 20e kdz file using LGUP to get back to stock Android 10.
Step 22: Now you are on Android 10 with unlocked bootloader, and Finger print works!


Again thanls to @Anand_Y, we got a better and faster way to get the FP working:
It is not such a big procedure. Today i did some testing too. Here are my findings/procedure:-
1. Assuming u guys are on android 10 unlocked bl. Downgrade to 10c using lg up.
2. Go to service menu, svc menu, handprint on.
3. Then imediately go to back to device test, saat, manual test, optical finger test, do the test. Press hard on fp till text turns green. Will say test failed. Still click yes.
4. Go to setting and fp starts working.
Thats it no restarts no nothing. You have fp in these few steps.

This is for LG G8x Indian Flipkart Big billion sale model.

To go into Service menu. open dialer and key *#546368#*850#

Thanks to @NABENDU1 for pooling the steps. Not sure who else tested but thanks to them!

All credits goes to @Anand_Y

Notes: Relocking bootloader is a huge risk, Always make sure you are on stock everything before doing it. Sometimes the device may brick. So make sure you understand the risks.
If I upgraded to the latest version after fixing the fingerprint using the method, will the fingerprint still work in lets say android 12?
 

Lukasz23

Member
Jul 15, 2022
6
0
Make sure you have backed up your 20e stock abl.

You will need to download the Android 9 kdz "G850EMW10c_00_1126.kdz"
link to Android 9 kdz:

If you are already on stock with locked bootloader, then start with step 5

Step 1: backup all parittions using qfil
Step 2: flash 20e kdz file using LGUP to get back to stock.
Step 3: flash engg abl in qfil
Step 4: go to fastboot and lock the bootloader.
Step 5: flash 10c (Android 9) using LGUP to go to Android 9
Step 6: Since you are on locked bootloader and Android now, FP works.
Step 7: Register pin and password and select secure pin to boot.
Step 8: Now reboot and enter incorrect pin for 30 times . this will reset ur device again (this is damn time taking)
Step 9: Now flash 20e kdz file using LGUP to get back to stock Android 10. (don'r register fp)
Step 10: flash engg abl in qfil
Step 11: go to fastboot and unlock the bootloader.
Step 12: flash 10c (Android 9) using LGUP to go to Android 9
Step 13: Now you are on unlocked Bootloader and Android 9
Step 14: Now try registering, it might fail.
Step 15: go to User Service menu -> Device test -> SAAT -> Service Menu -Manual Test - Optical Fingerprint test (test it few times)
Step 16: go to User Service menu -> SVC -> Enable FacePrint and Enable Handprint
Step 17: Try registering finger print in settings, it should work. If it doesn'r reboot and do the step 15 and 16 and try again.
Step 18: You must get the fingerprint working in Unlocked Android 9, that's the key
Step 19: It will work after some 1-2 times of step 15 and 16
Step 20: Register your finger print in unlocked Android 9. FInish the scan and set it up.
Step 21: flash 20e kdz file using LGUP to get back to stock Android 10.
Step 22: Now you are on Android 10 with unlocked bootloader, and Finger print works!


Again thanls to @Anand_Y, we got a better and faster way to get the FP working:
It is not such a big procedure. Today i did some testing too. Here are my findings/procedure:-
1. Assuming u guys are on android 10 unlocked bl. Downgrade to 10c using lg up.
2. Go to service menu, svc menu, handprint on.
3. Then imediately go to back to device test, saat, manual test, optical finger test, do the test. Press hard on fp till text turns green. Will say test failed. Still click yes.
4. Go to setting and fp starts working.
Thats it no restarts no nothing. You have fp in these few steps.

This is for LG G8x Indian Flipkart Big billion sale model.

To go into Service menu. open dialer and key *#546368#*850#

Thanks to @NABENDU1 for pooling the steps. Not sure who else tested but thanks to them!

All credits goes to @Anand_Y

Notes: Relocking bootloader is a huge risk, Always make sure you are on stock everything before doing it. Sometimes the device may brick. So make sure you understand the risks.
I have an lg velvet 4g (g910hm) with Android 11 did you know if there is any solution for my case?
 

Lukasz23

Member
Jul 15, 2022
6
0
Any chance this method would work on an LG Wing? I was directed here through some other posts. Fingerprint scanner wouldn't do anything at first, and after this it would recognize the finger but just say to put the entire finger on the screen. Can't install android 9 because it didn't ship with that, but I did everything else.
I have the exact same problem with my velvet 4g. My fingerprint doesnt work after unlocking the bootloader. I cannot make the downgrade because it was shipped with android 10. Dod you find any solution?
 

MeIsNoob

Member
Apr 6, 2014
19
2
Mars
LG G8X ThinQ
Make sure you have backed up your 20e stock abl.

You will need to download the Android 9 kdz "G850EMW10c_00_1126.kdz"
link to Android 9 kdz:

If you are already on stock with locked bootloader, then start with step 5

Step 1: backup all parittions using qfil
Step 2: flash 20e kdz file using LGUP to get back to stock.
Step 3: flash engg abl in qfil
Step 4: go to fastboot and lock the bootloader.
Step 5: flash 10c (Android 9) using LGUP to go to Android 9
Step 6: Since you are on locked bootloader and Android now, FP works.
Step 7: Register pin and password and select secure pin to boot.
Step 8: Now reboot and enter incorrect pin for 30 times . this will reset ur device again (this is damn time taking)
Step 9: Now flash 20e kdz file using LGUP to get back to stock Android 10. (don'r register fp)
Step 10: flash engg abl in qfil
Step 11: go to fastboot and unlock the bootloader.
Step 12: flash 10c (Android 9) using LGUP to go to Android 9
Step 13: Now you are on unlocked Bootloader and Android 9
Step 14: Now try registering, it might fail.
Step 15: go to User Service menu -> Device test -> SAAT -> Service Menu -Manual Test - Optical Fingerprint test (test it few times)
Step 16: go to User Service menu -> SVC -> Enable FacePrint and Enable Handprint
Step 17: Try registering finger print in settings, it should work. If it doesn'r reboot and do the step 15 and 16 and try again.
Step 18: You must get the fingerprint working in Unlocked Android 9, that's the key
Step 19: It will work after some 1-2 times of step 15 and 16
Step 20: Register your finger print in unlocked Android 9. FInish the scan and set it up.
Step 21: flash 20e kdz file using LGUP to get back to stock Android 10.
Step 22: Now you are on Android 10 with unlocked bootloader, and Finger print works!


Again thanls to @Anand_Y, we got a better and faster way to get the FP working:
It is not such a big procedure. Today i did some testing too. Here are my findings/procedure:-
1. Assuming u guys are on android 10 unlocked bl. Downgrade to 10c using lg up.
2. Go to service menu, svc menu, handprint on.
3. Then imediately go to back to device test, saat, manual test, optical finger test, do the test. Press hard on fp till text turns green. Will say test failed. Still click yes.
4. Go to setting and fp starts working.
Thats it no restarts no nothing. You have fp in these few steps.

This is for LG G8x Indian Flipkart Big billion sale model.

To go into Service menu. open dialer and key *#546368#*850#

Thanks to @NABENDU1 for pooling the steps. Not sure who else tested but thanks to them!

All credits goes to @Anand_Y

Notes: Relocking bootloader is a huge risk, Always make sure you are on stock everything before doing it. Sometimes the device may brick. So make sure you understand the risks.
I crossflashed my phone from TMO_US to OPEN_CA, A12, the only problem is I no longer have FP, I have a locked bootloader, my phone was dead for 2 weeks because I deleted the whole partition block, and luckily I did backup my LUN5 partition, I recovered my IMEI and S\N. do you think if I downgrade it to A10 my fingerprint will work again? What happens if I flash it to A12 again?
 

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    Make sure you have backed up your 20e stock abl.

    You will need to download the Android 9 kdz "G850EMW10c_00_1126.kdz"
    link to Android 9 kdz:

    If you are already on stock with locked bootloader, then start with step 5

    Step 1: backup all parittions using qfil
    Step 2: flash 20e kdz file using LGUP to get back to stock.
    Step 3: flash engg abl in qfil
    Step 4: go to fastboot and lock the bootloader.
    Step 5: flash 10c (Android 9) using LGUP to go to Android 9
    Step 6: Since you are on locked bootloader and Android now, FP works.
    Step 7: Register pin and password and select secure pin to boot.
    Step 8: Now reboot and enter incorrect pin for 30 times . this will reset ur device again (this is damn time taking)
    Step 9: Now flash 20e kdz file using LGUP to get back to stock Android 10. (don'r register fp)
    Step 10: flash engg abl in qfil
    Step 11: go to fastboot and unlock the bootloader.
    Step 12: flash 10c (Android 9) using LGUP to go to Android 9
    Step 13: Now you are on unlocked Bootloader and Android 9
    Step 14: Now try registering, it might fail.
    Step 15: go to User Service menu -> Device test -> SAAT -> Service Menu -Manual Test - Optical Fingerprint test (test it few times)
    Step 16: go to User Service menu -> SVC -> Enable FacePrint and Enable Handprint
    Step 17: Try registering finger print in settings, it should work. If it doesn'r reboot and do the step 15 and 16 and try again.
    Step 18: You must get the fingerprint working in Unlocked Android 9, that's the key
    Step 19: It will work after some 1-2 times of step 15 and 16
    Step 20: Register your finger print in unlocked Android 9. FInish the scan and set it up.
    Step 21: flash 20e kdz file using LGUP to get back to stock Android 10.
    Step 22: Now you are on Android 10 with unlocked bootloader, and Finger print works!


    Again thanls to @Anand_Y, we got a better and faster way to get the FP working:
    It is not such a big procedure. Today i did some testing too. Here are my findings/procedure:-
    1. Assuming u guys are on android 10 unlocked bl. Downgrade to 10c using lg up.
    2. Go to service menu, svc menu, handprint on.
    3. Then imediately go to back to device test, saat, manual test, optical finger test, do the test. Press hard on fp till text turns green. Will say test failed. Still click yes.
    4. Go to setting and fp starts working.
    Thats it no restarts no nothing. You have fp in these few steps.

    This is for LG G8x Indian Flipkart Big billion sale model.

    To go into Service menu. open dialer and key *#546368#*850#

    Thanks to @NABENDU1 for pooling the steps. Not sure who else tested but thanks to them!

    All credits goes to @Anand_Y

    Notes: Relocking bootloader is a huge risk, Always make sure you are on stock everything before doing it. Sometimes the device may brick. So make sure you understand the risks.
    2
    I'm on V20d with my european LG G8X and fixing FP didn't work for me. To which version do I have to downgrade or did I make something wrong?
    Thanks and best regards.
    To the first firmware available for your model number and region.
    1
    But after step 4 we are still in android 9, right? Then how to revert back to android 10.. Via OTA or flashing 20e firmware?

    Yes, if you want to go to 10 then u need to flash via LGUP.
    1
    Please clarify if only way to receive all the OTA updates that was pushed to the phone is by finding the KDZ and using LGUP. I assume the OTA no longer work since the phone already has received the updates previously and by downgrading it will never get the automatic update?

    One other question, can we use KDZ from say the US for the Canadian variant to downgrade? Is there any side effects from using it or if OTA is still good after, would it then update based on IMEI region?
    It's simple, after Bootloader unlocked, Fingerprint sensor stops working, for that to work, you have to downgrade your device with the first firmware available for your model number and region. Once the FP Sensor is made to work in that downgraded firmware, flash the device with the latest firmware available for your model number and region. And Cross flashing of various firmware will have it's own side effects, even stuck with boot logo or boot-looping, may work even to surprise you. I hope this makes you to understand some of what you wanted to .....