Chosen Solution

Hey guys have replaced the screen (whole unit with frame) on this Xiaomi Mi 9 afterwards the fingerprint Sensor did not work properly. It hardly Scans the initial fingerprint but won’t unlock the phone with it or allow any other fingerprint functions. I have already removed it and replaced it again. as it is embedded into the Display Unit I Wonder if this is a problem concerning the display unit or the fingerprint scanner itself. if it is the fingerprint scanner, would it even be possible to replace it or is it like on iPhones „married“ to the motherboard? would appreciate your support guys keep fixing peace

Exactly the same here. Bought Frame + Display on ebay (Germany). Everything works perfect except the fingerprint sensor. “Learning” a finger is hard. Only every 10th scan is recognized. Other 9 fail with messages like “too fast” or “dirty sensor”. Unlock has two different behaviors:

  1. On ambient display: It never works (which previously did). The sensor “scans” for around 300 milliseconds and fails. With the old display it took the same amount of time but it worked.
  2. After pressing power button: It takes about 1 second (which is a really long time) for the scan to be completed but works most times (9 out of 10). Previously it worked much faster. /edit Just found out that it does NOT work properly in the “power on button” state. After 1 second the device gets unlocked, BUT it also gets unlocked with unknown fingers! Maybe it focusses something in the display?

Apparently the latest software blocks the figure print replacement from working.

I’d first check if the fingerprint sensor or the scan hole are dirty, and clean them. Afterwards, try erasing all the fingerprints and re-adding them. It’s possible that a software update started to pair displays to the motherboard, so one way of fixing this would be using a custom ROM. Hope this helps.

https://www.youtube.com/watch?v=9jKmbfP2… This is work propertly :)