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Steps to get the Fingerprint working with unlocked bootloader and Root

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raj_ch2002

Senior Member
Dec 31, 2011
480
526
Bangalore
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.
 
Last edited:

raj_ch2002

Senior Member
Dec 31, 2011
480
526
Bangalore
Update 1:
guys, I understand from @NABENDU1 that we don't need to go to android 10 to use eng abl for unlocking and we can do it via android 9, you can skip step 9 and step 12 from the initial steps. remove those 2 and follow the order.


Not needed with new method
 
Last edited:

Narendra_Rudach

New member
Dec 15, 2020
1
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.
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?
 

zhlvf

Senior Member
May 15, 2012
67
8
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.
 

lefttobleed

Senior Member
Apr 20, 2010
316
71
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.
Can the Pie ROM be used on all models or just the India one? There is no pie ROM for Canadian G8X on lg-firmwares :(
In your case u will have to test yourself. First try the first android 10 firmware for Canada. If that doesnt work try first pie version for your phone model number but different region.
Best of luck.
 
Yes, if you want to go to 10 then u need to flash via LGUP.
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?
 
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 .....
 
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Reactions: pierro78
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 .....
Thanks for the great suggestion.
I took a stab and did exactly that. The lesson learn was really helpful. I now know there is pretty safe reset root when you mess up with abl and boot. As long as you can still go to the LG Download mode, we can use LG UP to downgrade and start again.
 

zdanee

Senior Member
Sep 27, 2012
88
16
Confirmed working on an EU (Hungary) version. Had to use the command-line LGUP tool (1.17) and not the oldest Pie version ROM but the G850EMW10d_00_0131.kdz version instead. After that I could go back up to Android 10 V20h and both the FP and audio is fixed.
 

james508959

New member
May 28, 2021
4
0
Currently on unlocked android 9 (10b TWN version, only kdz I could find for my variant)
Tried the simplified 4 steps, still cannot get fingerprint to work.
What else can I try?
 

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  • 15
    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 .....