The sudden failure of biometric unlock on Xiaomi and Redmi smartphones is one of the most annoying problems users face. It would seem that yesterday the phone instantly responded to touch, and today the screen continues to glow, ignoring attempts to enter a fingerprint. This may be caused by a software failure after the update. MIUI or HyperOS, and physical damage to the plume when the device falls.
Before you bring your device to the service center, you need to eliminate software errors, which account for more than 60% of all cases of a broken sensor. Often the problem lies in the crowded cache of the fingerprintd system process or the conflict of access rights after installing third-party launchers. In this article, we will discuss in detail the algorithm of actions that will help return functionality to the scanner without unnecessary costs.
However, if software methods don't work, it could be a more serious malfunction. In models with a scanner in the power button, such as the Redmi Note 9 Pro or Xiaomi Mi 10T, a common cause is oxidation of contacts or the departure of the plume from the board. Understanding the nature of the malfunction will allow you to choose the right solution, from simply resetting to replacing the module.
Primary diagnosis and checking settings
The first step should always be to check the basic system settings. Sometimes users accidentally turn off the unlock function or change the priority of authorization methods. Go to the Settings menu → Passwords and Security → Unlock from the fingerprint and make sure that the switch is active. If the slider is gray or the system asks for a password to turn on the function, this may indicate a critical driver error.
It is also worth checking whether the “Increased Security” mode is included, which requires mandatory entry. PIN-In some cases, it helps to remove old fingerprints and re-write. Try to scan your finger from different angles without pressing it too hard, because the sensor calibration may have been confused.
💡
Before re-recording the fingerprint, thoroughly wipe the scanner and finger with an alcohol napkin. Fat spots and moisture are the main enemies of optical sensors, which are often mistaken for damage to glass.
Notice the vibration behavior. If you touch the scanner area, the phone gives you a short vibrating response but it doesn't unlock, it's physically sound and it can see the touch, but it can't match the image to the reference, and in this case, the problem is the software or the pollution, and the lack of any response (vibro or sound) is more likely to be the hardware part.
It's important to check if the scanner works in other applications, like trying to log in to Google Pay or a banking app, and if it's reading the print and there's no settings in the settings menu, it's a problem with the specific MIUI system process, and if there's no response, you need to do a deep diagnostic.
Software solutions and service reset
If the basic settings don't work, you need to do a deeper reset of the system security services. In the MIUI shell, not only the visible interface but also the hidden system processes are responsible for the operation of the biometrics. Cleaning up these processes often returns the scanner to work without losing the user's personal files.
To do this, go to Settings → Applications → All Apps. In the upper right corner, click on the menu icon (three dots) and select Show System Processes. In the list that opens, find an app called Security or Security, and Fingerprint Extension Service.
☑️ Security services reset algorithm
Once these components are cleaned, the phone can behave strangely: all stored fingerprints may disappear, and the settings menu will need to re-accept privacy agreements. This is normal behavior. The system will reinitiate the TEE (Trusted Execution Environment) security module and create new encryption keys for biometrics.
In some cases, especially after a firmware update, network and Bluetooth settings may need to be reset, as they are also tied to shared security modules. Go to Settings → Connection & Sharing → Reset Wi-Fi, mobile networks and Bluetooth. Note that this action will remove saved Wi-Fi passwords and associated Bluetooth devices.
Specificity of scanners in the button and under the screen
The scanning technologies in Xiaomi smartphones vary, and the methods of repairing or adjusting them depend on the type of sensor. Budget and medium-sized models (Redmi Note series, Poco M) often use a scanner built into the on button. In more expensive models (Xiaomi 13, 14, Mi 11), an optical or ultrasonic scanner is used under the screen.
The scanners in the power button are physically connected to the motherboard with a flexible plume, and a common problem with these devices is that the button contacts oxidize because of moisture or just time. If you notice that the power button has become stuck or has a backlash, there's a high probability that the problem is precisely the mechanics, in which case the software reset is unlikely to help.
⚠️ Note: If you have a scanner under the screen, do not try to stick thick protective glass with a black frame that covers the scanning area.
For optical scanners under the screen, the condition of the display is critical. If there is a crack in the scanner area or a severe scuffling of the protective layer (oleophobic coating), the reading quality drops sharply. The light from the backlight is distorted, and the sensor cannot build a clear picture of the topography of the finger, in which case only replacing the protective glass or the entire display module helps.
Also worth mentioning are the ultrasonic scanners used in flagships. They're less sensitive to contamination, but very demanding on the quality of protective films. Using cheap films can completely block ultrasound. Always check the compatibility of accessories with your Xiaomi model.
Table: Comparison of scanner types and their vulnerabilities
To better understand the nature of your problem, check out a comparison chart that will help you determine whether you are likely to have a software failure or whether you should be preparing for a repair.
| Type of scanner | Location. | Frequent causes of failure | Probability of F-fix |
|---|---|---|---|
| Capacitive | Power button/back | Oxidation of the plume, mechanical wear of the button | Low (30%) |
| Optical | Under the screen | Screen pollution, cracks, poor quality film | Average (50%) |
| Ultrasonic. | Under the screen (Flagships) | Conflict software, thick protective glass | High (70%) |
| Infrared (Face ID) | Screen bangs | Sensor contamination, calibration failure | High (80%) |
As you can see from the table, device owners with button scanners are more likely to experience physical damage, while users of flagships with subscreen sensors are more likely to deal with software conflicts or accessory problems, and this knowledge helps to focus efforts on the right direction of diagnosis.
If your case falls into the category of "Low probability of Fixed Software," don't spend much time flashing it over. It's better to check the plume immediately or consult a specialist. Attempting to "cure" oxidized contact with software methods is pointless and can lead to a waste of time.
Hardware problems: plume and oxidation
When software methods are exhausted, there is a hardware malfunction option: In Xiaomi smartphones with a side scanner, the fingerprint module is connected to the motherboard with a thin plume. When falls, even without visible damage to the body, this plume can move away from the connector or get a microcrack.
To test this hypothesis requires partial disassembly of the device, and it is important that before opening the case, be sure to turn off the phone and remove it. SIM-You're going to need a thin plastic spatula, a suction cup and a set of screwdrivers. Carefully warm up the edges of the case with a hairdryer (not overheating the screen!) to soften the glue, and remove the back cover.
Instructions for safe disconnection of the plume
Often, the cause of failure is oxidation of contacts. If the phone is in high humidity or spilled, the plume and connector contacts may have green or white plaque. Cleaning contacts with isopropyl alcohol and a soft toothbrush often brings the device back to life. Let the alcohol dry completely before assembly.
If the scanner didn’t work after reconnecting and cleaning, the module itself may have failed. Button fingerprint scanners on Xiaomi and Redmi often don’t have a personalized connection to the board (unlike some other brands), so they can be replaced with a donor-like or a new one. However, in new models with subscreen scanners, the situation is more complicated: there the module can be integrated into the display or require software binding.
Radical measures: resetting and reflashing
If you are sure that the hardware is working, but the scanner still does not work, there is a complete reset to factory settings.This action will delete all your data, photos and contacts, so be sure to back up. Go to Settings → About Phone → Settings Reset → Erase all data.
Once reset, the phone will go back out of the box. If the fingerprint scanner fails to work at this point in the initial setup, the probability of a software error in user data or application conflicts will be zero, and the problem is likely to be deeper, in the system partition damage or a physical defect.
⚠️ Note: Do not try to reflash the phone with custom recaveri (TWRP) Or global firmware on the Chinese version, if you don't have experience, the wrong firmware can permanently lock the security module, and the scanner will stop working even after the drain returns.
In extreme cases, even when the factory firmware doesn't work, it might require soldering the scanner module or restoring the circuits on the board, and it's a job for skilled engineers with a microscope and soldering equipment. BGA-Components without experience are not recommended.
Sometimes the "people's" method of calibration through the engineering menu helps, but it does not work on all versions of MIUI. Try typing the code ##6484##. If the engineering menu opens, find the Fingerprint test and follow the instructions on the screen to recalibrate the sensor.
💡
If after a complete reset (Wipe Data) and check in the engineering menu, the scanner does not respond - in 95% of cases, this is a physical failure of the module or plume, requiring a replacement part.