Mi6 Can't Add Fingerprint

[szikak245]

Can't add fingerprint to unlocki my device. When i trying to add fingerprint i got a message like this "Failed to add a fingerprint. try again". Whne i use a advanced diagnostic tool i got something like this:

I got mi6 from 2 days

MIUI version - Global 8.2 Stable (8.2.2.0) NCAMIEC

 

[Cecco]

Try a factory reset

 

[szikak245]

Try a factory reset

I already tried

 

[nullpointer]

Can't add fingerprint to unlocki my device. When i trying to add fingerprint i got a message like this "Failed to add a fingerprint. try again".

Similar issue here: I had already added 3 fingerprints and suddenly only my thumb worked, also only maybe 1 of 3 times. Flashed back to China Dev, everything ok again. Flashed back to Xiaomi.EU, it worked for like 12 hours, then issues again and only 1 finger gets detected. Sometimes not at all.

I went to hardware test too and it shows same error! I can provide logcat from failed unlock if you need it.

 

[Hitardo]

Usually it is a software bug.

You should change the way you unlock your phone (to bypass the fingerprint), e.g. form pattern to PIN or vice-versa, and it should work again.

 

[szikak245]

Usually it is a software bug.

You should change the way you unlock your phone (to bypass the fingerprint), e.g. form pattern to PIN or vice-versa, and it should work again.

Still not working :/ I guess i wait for update to miui 9.

 

[nullpointer]

Still not working :/ I guess i wait for update to miui 9.

Hey man,

for me it started working again today! I did some workarounds yesterday: delete screen lock, also delete pin and everything. Let phone drain to 0% until it shuts off. Start it up like 10 times, you will see MI logo and it tries to boot and then shuts off because of low battery. After you do this a couple of times, only battery logo will flash. Repeat until you don't see battery logo and only LED lights up. So battery is completely empty. Let it sit with dead battery for 2-3 hours. Then, while off, charge it to 100%. Oh also I put some pressure on fingerprint sensor before turning it on.

I did every hardware test after, screen, flashlight, etc. Still got same result on the last FPC test as you did, but it's working perfectly again!! I think this last hardware test doesn't have to get passed. Now it's working 99% of the time with all 3 fingers I registered.

Maybe it was just luck, but this is what I did.

 

[Hitardo]

Let phone drain to 0% until it shuts off. Start it up like 10 times, you will see MI logo and it tries to boot and then shuts off because of low battery. After you do this a couple of times, only battery logo will flash. Repeat until you don't see battery logo and only LED lights up. So battery is completely empty. Let it sit with dead battery for 2-3 hours.

Do not do that!
This will arm your battery really hard.

Try one or all:
- Wipe Cache / Dalvik cache;
- Wipe Data;
- Reflash official ROM;
- Flash Xiaomi.eu ROM.

But do not drain your battery to 0%!

 

[nullpointer]

Do not do that!
This will arm your battery really hard.

Try one or all:
- Wipe Cache / Dalvik cache;
- Wipe Data;
- Reflash official ROM;
- Flash Xiaomi.eu ROM.

But do not drain your battery to 0%!

Let me elaborate. First off, I tried flashing China Dev, Full Wipe, everything. Same issue, so it's not the ROMs fault. Maybe the FP sensor has it's own storage or something, I don't know.

OFF TOPIC: Now to the battery: I know a bit about Lithium based batteries. Discharging Lithium Polymer batteries to a very low voltage can absolutely harm them, yes. But please understand how modern smartphone charging circuits work:

Most LiPo batteries have a nominal voltage of 3.7V, newer ones, as the one in Mi6 even 3.85V. That means that this battery can operate well in the range between about 3.1 and 4.4V. It's recommended to keep it as close to 3.85V as possible (charge from 30-80%, not 0-100%) but it is no big problem if it drops to 3.1V, if you don't do this every day. Now your modern smartphone has a protection circuit. You can check for yourself. Download "Ampere" from Google Play and check voltage. If you charge to 100%, your voltage will reach about 4.3V, so even less than the maximum. Also, if you drain your battery to 1% it will still have a voltage of about 3.3V. Now, to really discharge the battery, you need to boot up the phone a couple of times to get that voltage even lower. As soon as the voltage hits the minimum (3.1V) the device won't turn on and the LED will flash, as I said in my post. This is the protection circuit kicking in and preventing a voltage drop unter 3.1V. So even when your phone shows 0%, it has still much juice left. Even when it doesn't boot up anymore, you still have some more than 3.1V.​

Don't do this everyday, sure, but please don't spread any fear. I know a bit about LiPos and todays smartphone batteries are pretty much foolproof. Also this workaround isn't my creation, just read on the OnePlus or Samsung forums about FP scanners that stopped working. Draining the battery and charging it up again fixes it for many people.

 

[Hitardo]

Let me elaborate.

Don't do this everyday, sure, but please don't spread any fear. I know a bit about LiPos and todays smartphone batteries are pretty much foolproof. Also this workaround isn't my creation, just read on the OnePlus or Samsung forums about FP scanners that stopped working. Draining the battery and charging it up again fixes it for many people.

Thank you for your clarification.

Yes, what you said is true.
But I fear that many people try this often, risking arming their phone.
Especially due to the protection circuit.
You can see on the OnePlus forum many people that have triggered their protection circuit due to low battery and were very scared when they connected their phone to the wall charger and it did not woke up.
Only after several minutes it woke up, as the protection circuit reacts to a charging state for the battery.

I defend that first your should try every other method.
Only after that, you should go with the battery one.

But, the phones is yours and your are allowed to do what you intend to do and what you fell is more adequate to your situation.

 

[nullpointer]

I defend that first your should try every other method.
Only after that, you should go with the battery one.

You are absolutely right about that. For most issues, a data wipe or ROM reinstallation fixes most issues. Not for me though, so there had to be another issue than just a bug in ROM. Good on you for being cautious though, deep discharge is indeed harmful to batteries if done often.

 

[szikak245]

Hey man,

for me it started working again today! I did some workarounds yesterday: delete screen lock, also delete pin and everything. Let phone drain to 0% until it shuts off. Start it up like 10 times, you will see MI logo and it tries to boot and then shuts off because of low battery. After you do this a couple of times, only battery logo will flash. Repeat until you don't see battery logo and only LED lights up. So battery is completely empty. Let it sit with dead battery for 2-3 hours. Then, while off, charge it to 100%. Oh also I put some pressure on fingerprint sensor before turning it on.

I did every hardware test after, screen, flashlight, etc. Still got same result on the last FPC test as you did, but it's working perfectly again!! I think this last hardware test doesn't have to get passed. Now it's working 99% of the time with all 3 fingers I registered.

Maybe it was just luck, but this is what I did.

can't get to the point to make the LED flash. I make battery to 0% when i try to start up i get a flash of mi logo and battery trying turn on like 50 times and still dont get a LED only ;/

[EDIT]

Finally i go to the point when nothing shows, even the LED

 

[nullpointer]

[EDIT]

Finally i go to the point when nothing shows, even the LED

Try to let it sit for an hour or two, then recharge while off. When turning on, delete screen lock/fingerprint settings. Do all hardware tests on first page, use some pressure on fp sensor, but not too much. I don't know which of that helped, but now it works

 

[szikak245]

Try to let it sit for an hour or two, then recharge while off. When turning on, delete screen lock/fingerprint settings. Do all hardware tests on first page, use some pressure on fp sensor, but not too much. I don't know which of that helped, but now it works

OOOOO YEAH ! Works perfect ! Thanks a lot for help am guessing the pressure on FP is the wey to fix it. first dont works but when i push a little harder it help

 

[nullpointer]

OOOOO YEAH ! Works perfect ! Thanks a lot for help am guessing the pressure on FP is the wey to fix it. first dont works but when i push a little harder it help

No problem! Such a weird bug, I hope it stays like this now

Gesendet von meinem MI 6 mit Tapatalk

 

[arbabseyfola]

Try this solution:en.miui.com/thread-925600-1-1.html