This post is just for reference, in case anyone needs pictures of original parts and a small guide on how to replace the fingerprint sensor.
This video (not mine) shows the process as well, on a Redmi 4 (non-X), except you don't need a screwdriver for the 4X. And there's no fp sensor test in the 4X MIUI engineer test app.
I recently bought a Redmi 4X with a faulty fingerprint sensor.
I noticed in both MIUI11 and LineageOS:
- I was not asked to add a fingerprint during initial setup
- There are no fingerprint settings for lockscreen security (only PIN, pattern, swipe). If you try to search in settings for "finger" and tap on the result, the page will be empty/blank.
I tried some software tricks like deleting files, but that did not help here. On the phone itself, the fp sensor had a tiny dent/hole in it (can be seen on the pictures), less than 1mm in size, which revealed a bit of silver colour under the black surface. Looks like it hit some sharp object. I'm not entirely sure if that caused it to fail though.
So I bought a replacement (less than $10, pictures attached). After opening the phone with plastic tools, removing the old fp sensor ribbon cable from the motherboard, just push the old sensor out of the case through the hole with moderate force. It is glued in place with some sort of foam, clean it off with some tweezers and isoprop alcohol. I installed the new sensor with some B-7000 glue (if you make any mistakes with B-7000, just wipe it off before it dries with a qtip and isoprop alcohol and try again).
My replacement seems to be the common one sold on Aliexpress and elsewhere, it works fine and appears to be fpc (persist.sys.fp.goodix is 0).
Text on original Xiaomi fp sensor ribbon cable (ribbon cable has a black colour):
F3208FD RA0
F 171501
Text on replacement (ribbon cable has copper/bronze colour):
[icon]-film 0251-00 V4HX-1718
This video (not mine) shows the process as well, on a Redmi 4 (non-X), except you don't need a screwdriver for the 4X. And there's no fp sensor test in the 4X MIUI engineer test app.
I recently bought a Redmi 4X with a faulty fingerprint sensor.
I noticed in both MIUI11 and LineageOS:
- I was not asked to add a fingerprint during initial setup
- There are no fingerprint settings for lockscreen security (only PIN, pattern, swipe). If you try to search in settings for "finger" and tap on the result, the page will be empty/blank.
I tried some software tricks like deleting files, but that did not help here. On the phone itself, the fp sensor had a tiny dent/hole in it (can be seen on the pictures), less than 1mm in size, which revealed a bit of silver colour under the black surface. Looks like it hit some sharp object. I'm not entirely sure if that caused it to fail though.
So I bought a replacement (less than $10, pictures attached). After opening the phone with plastic tools, removing the old fp sensor ribbon cable from the motherboard, just push the old sensor out of the case through the hole with moderate force. It is glued in place with some sort of foam, clean it off with some tweezers and isoprop alcohol. I installed the new sensor with some B-7000 glue (if you make any mistakes with B-7000, just wipe it off before it dries with a qtip and isoprop alcohol and try again).
My replacement seems to be the common one sold on Aliexpress and elsewhere, it works fine and appears to be fpc (persist.sys.fp.goodix is 0).
Text on original Xiaomi fp sensor ribbon cable (ribbon cable has a black colour):
F3208FD RA0
F 171501
Text on replacement (ribbon cable has copper/bronze colour):
[icon]-film 0251-00 V4HX-1718
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