When a fingerprint scanner on a Xiaomi smartphone suddenly stops working, it can be taken by surprise, especially if you are used to quickly unlocking the device. Instead of instant access to the system, the user faces ignoring touch, long waiting or erroneous messages about the wrong fingerprint.
Biometric problems in the MIUI shell or the new HyperOS can be both software and hardware, most often due to contamination of the sensor surface, software failure after updating or drivers malfunction, but in rare cases, it can be a physical damage to the module, which will require the intervention of specialists of the service center.
In this article, we will take a look at all the possible reasons why your fingerprint doesn’t work, and provide step-by-step troubleshooting instructions, learn how to calibrate your sensor, clean your system debris, and understand when it’s time to carry your phone for repair.
The main reasons for failure of biometric unlocking
The first thing to do when you have a problem is to analyze the previous events, and if you have recently dropped your phone or poured water on it, there is a high probability of mechanical damage to the plume or the sensor itself, and in such cases, software treatments may be useless, and a diagnosis of the hardware part is required.
On the other hand, if the phone fell in the case and visually intact, the problem can be hidden in the software. Updating the Android firmware or the MIUI shell sometimes leads to a conflict of security drivers. The system can simply "forget" how to read data correctly from the module (fingerprint), which is solved by restarting or resetting settings.
Dirty hands, moisture, sweat or fat on the surface of the finger significantly reduce the accuracy of reading, and optical scanners embedded in the screen are especially sensitive to the quality of the display surface and protective film.
A common cause is the use of poor-quality protective glasses, and if the glass is too thick or has a low-quality oleophobic coating, the light from the scanner does not pass through it with the required intensity, and as a result, the proximity sensor and the fingerprint scanner cannot properly focus on the skin pattern.
⚠️ Warning: If the phone has been subjected to severe heat or impact, and the scanner stopped working exactly after that, do not try to disassemble the device yourself if you do not have experience.
Problems with protective films and covers
One of the most common but often ignored reasons is the physical obstacle between the finger and the sensor. Xiaomi smartphones with underscreen scanners use optical reading technology that is extremely sensitive to any distortion of light. Cheap protective films can have microscopic irregularities that knock down recognition algorithms.
If you're using a case, make sure it doesn't cover the edge of the scanner, especially in models with side unlock buttons. Even millimeter shifts can cause the finger to touch the frame rather than the active area, and in such cases, calibration won't help, you need to change the accessory.
For owners of devices with a subscreen scanner, there are special "hydrogel" or thin glass films marked "Fingerprint Friendly". Conventional thick glass can block up to 40% of the light flux necessary to read the pattern of papillary lines.
Try temporarily removing the protective glass and checking the sensor, and if the problem is gone, it means that it was the accessory, and some Xiaomi models have a screen sensitivity feature that can partially compensate for the effect of the film.
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Try adding the same finger to the system twice under different names (e.g., "Finger 1" and "Finger 1 copy"), which will increase the fingerprint database and increase the likelihood of successful unlocking.
Software failures and system updates
Software errors are the second most common factor: after a major update to MIUI or Android, some system services may not work properly, especially when switching between major versions of the OS. In the background, there may be processes that block access to the security module.
The first step in suspected software is a banal but effective reboot, which clears RAM and restarts all system services, including biometric drivers, and if that doesn't work, check for more recent security patches in the update menu.
Sometimes third-party applications with access to the camera or security system conflict, antiviruses, ad blockers or launchers can interfere with the authentication process. Try to start the phone in Safe Mode to eliminate the influence of third-party software.
If the problem occurs after installing a particular application, delete it and check the scanner. It is also worth clearing the cache of the system application "Security" or "Settings", but you need to do this carefully so as not to bring down other system parameters.
How to get into Safe Mode on Xiaomi?
Setup and recalibration of the print
If (hardware) is good, but the phone continues to be wrong, it may be time to re-introduce the fingerprint. Old data may have been damaged or rendered irrelevant by micro-changes in the finger skin (dry, calluses, cuts).
When you re-record a fingerprint, follow the rules: put your finger in different areas, not just the center, but also the edges. The system should build a volumetric model. Take your time, let's vibrate each step of the recording.
Some Xiaomi models have a hidden hardware engineering menu available. To get there, type ##6484## in the Phone app. In the CIT menu that opens, select Fingerprint to test, and see if the system sees the module itself.
☑️ Checklist of correct print recording
It's important to understand that the security algorithms in Xiaomi are pretty strict. If you've recorded a print with dirty hands or in a hurry, the match percentage will be low. It's better to spend 2 minutes on a quality record than torment yourself with unlocking every day.
Table: Comparison of scanner types on Xiaomi
Understanding the type of scanner you have helps diagnose the problem more quickly, and optical, capacitive, and ultrasound sensors have different vulnerabilities and operating requirements.
| Type of scanner | Location. | Sensitivity to water | Frequent problems |
|---|---|---|---|
| Optical (in screen) | Under the display | High (works poorly with wet hands) | Responds to bright wallpaper, requires a bright screen |
| Capacitive (side/back) | Power button/separately | Medium | It works from accidental touches in your pocket. |
| Ultrasonic (rarely) | Under the display | Low (works with wet hands) | Conflicts with thick protective glass |
As you can see from the table, optical scanner owners (most of today’s Xiaomi) should be especially attentive to the brightness of the screen and the purity of the surface. Optical scanners use light to read, so any dirt on the screen acts as noise to the camera.
Resetting and radical measures
If none of the above has worked, there is a software reset option, which is a last resort, as it will delete all data from the device.Be sure to back up in the Mi Cloud cloud or on your computer before you start.
Resetting to factory settings (Wipe Data) puts the phone back out of the box. This is guaranteed to eliminate any software conflicts, viruses or errors in system files. If after a complete reset, the scanner does not work, it is 99% hardware failure.
To perform the reset, go to Settings → About Phone → Reset. Select “Erase All Data.” The process will take a few minutes, after which the phone will suggest an initial setup.
⚠️ Warning: Before resetting, make sure you remember the password from your Mi Account and Google account.Without them, you won't be able to activate your phone after reset due to security system FRP.
When repairs are needed in the service center
There are a number of signs that the software repair is powerless: If the scanner test shows an error or freezes in the CIT, the module itself is likely to have failed or the plume has gone.
Physical damage, such as cracks in the scanner area, moisture entering the body (even if the phone is moisture-proof, leakage is broken over time), require replacement of components. In modern smartphones, the scanner is often integrated into the display module or tightly glued to it, which complicates repair.
The cost of replacement varies. For side-scanner models, this is an inexpensive procedure. For phones with a subscreen scanner, replacement may require repainting the display or complex soldering, which is not always economically feasible.
Don't try to heat the back cover with a hair dryer or push hard on the screen, hoping to "revive" the contact. This can cause the battery to bloat or the display to fail permanently. Trust the diagnostics to the professionals.
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If the reset to the factory settings and check in the engineering menu did not give a result, the problem is of a physical nature and requires replacing the scanner module or plume.