How to check if the fingerprint scanner works on Xiaomi smartphones: from tests to repairs

The fingerprint scanner in Xiaomi smartphones is not just a convenient way to unlock, but also a key security element. When the sensor suddenly stops responding to touch or gives an error “I couldn’t read the fingerprint”, many users are lost: whether the problem is a software failure, or a physical failure of the module. In this article, we will examine all the ways to check the scanner’s health, from basic tests to diagnostics through the engineering menu, and also tell you when to contact the service center.

It’s important to understand that the verification algorithm depends on the Xiaomi model and the type of sensor: optical sensors (like the Mi 11 or Redmi K50) are tested differently than ultrasonic or capacitive ones. We have compiled universal methods that will work for most devices, from the budget POCO M4 Pro to the flagship Xiaomi 14 Ultra. If after checking it turns out that the sensor is faulty, you will learn how to distinguish hardware from software failure and what to do next.

1. Quick check through Android settings

The first and easiest way is to use the standard fingerprint menu, which requires no additional tools and works on all Xiaomi smartphones running MIUI (including global and Chinese versions).

Go to Settings → Passwords and Security → Fingerprint. If you don’t have a fingerprint, your model doesn’t support it (like the Redmi 9A or POCO C31). If the menu opens but the sensor doesn’t respond to touch, pay attention to the following:

• 🔴 Error "Fingerprint sensor does not respond" - possible software failure or physical damage to the module.
• 🔵 The message “Put your finger on the sensor” does not disappear – the sensor does not recognize the touch (check the cleanliness of the surface).
• 🟢 Successful fingerprint addition, but unlocking doesn’t work – the problem may be firmware or security settings.

If the sensor doesn't respond at all, try restarting your smartphone -- sometimes it helps with temporary crashes. If things haven't changed after the reboot, move on to the next method.

Testing through the Engineering Menu (#4636##)

The Engineering Menu (EngineerMode) allows you to check the hardware status of the sensor without root rights. This method is suitable for most Xiaomi models, but some devices (for example, with MIUI 14+) may require activation via ADB.

To open the menu:

1. Enter the combination in the Phone app: ##4636###.
2. Select Testing (or “Testing”).
3. Scroll down to the Fingerprint section (may be called the Fingerprint Sensor).
4. Press Test and monitor the sensor response.

Ideally, after touching your finger, you should see:

• 🟢 Green checkmark or Success sign – the sensor works correctly.
• 🟡 Yellow Exclamation Point – The sensor recognizes touches, but there are reading errors (possibly contamination).
• 🔴 Red Cross or Failed – the sensor is faulty or disabled at the system level.

If the Fingerprint section is not on the engineering menu, it can mean:

• 📱 Your model does not support testing through this menu (e.g., your model does not support testing, POCO X3 Pro with side sensor).
• 🔧 Firmware modified (castomy software may hide some options).

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If the engineering menu doesn’t open, try entering the combination ##6484##, which is an alternative code for testing hardware modules on some Xiaomi.

3.Verification through Hidden MIUI Codes

Xiaomi uses unique service codes to diagnose equipment, which allow you to get more detailed information about the state of the sensor than the standard settings.

Once you enter the code, you will see a log screen or an interactive test, for example, the code ##64663## on the Redmi Note 12 Pro+ displays the following:

• 📊 Status: OK or NG (faulty).
• 🔢 Sensor ID: Unique sensor identifier (if not available, the module is not recognized by the system).
• 🔄 Test Result: Percentage of successful reads (below 80% is a bad signal).

If nothing happens after entering the code, check:

• ❌ Not supported by your firmware (especially relevant to your MIUI EU custom-assembly).
• 🔒 Codes disabled by the manufacturer (on some models for the Chinese market).

4.Diagnostics via ADB (for advanced users)

If standard methods fail, you can use Android Debug Bridge (ADB), a low-level diagnostic tool that requires a computer and minimal command line knowledge, but provides the most accurate information about the state of the sensor.

To check the scanner through ADB:

1. Enable USB Debugging in the Developer Settings → About Phone → MIUI Version – Press 7 times, then go back to Additional Settings → For Developers.
2. Connect your smartphone to your PC and open the terminal (or Command Prompt in Windows).
3. Enter the command: adb shell dumpsy fingerprint

In the answer, pay attention to the following parameters:

• mSensorId: Sensor identifier (if 0 is not detected).
• mSensorState: state (IDLE - ready to work, ERROR - malfunction).
• mAuthenticatedFingerprints: A list of saved fingerprints (if empty, but you added fingers – a data storage problem).

If there is a line in the logs:

E/FingerprintService: Fingerprint sensor not available

This means that the system does not see the physical module – most likely the problem is in the plume or the sensor itself.

For a deeper diagnosis, you can use the command:

adb shell service call fingerprint 1

Result: Parcel(00000000 00000001)

Install Xiaomi drivers on PC

Enable debugging over USB on your phone

Download ADB Tools (e.g. Google Platform Tools)

Connect your phone with the original cable (not all) USB-cables support data transmission)

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5. Physical inspection of the sensor: what can be done on your own

If software tests show that the sensor is not responding, it may be that the problem is physical damage or contamination of the module.

• 🧹 Clean the sensor surface: use soft lilaless fabric and alcohol (not acetone!). For optical sensors (under the screen) a special wipe for glasses will suit.
• 🔍 Cracking check: inspect the glass above the sensor (on models with a subscreen scanner) or the module itself (on the back.
• 🔌 Overheat/cooling test: If the smartphone overheated (e.g. while charging), the sensor could temporarily shut down.
• 🛠️ Checking the plume (for versers): if you are confident in your abilities, you can carefully disassemble the phone and check whether the sensor plume has moved away from the motherboard.

Pay special attention to models with built-in scanner (for example, Xiaomi 13T or Redmi K60).

• 💡 Bright sunlight (may interfere with reading).
• 🎨 Thick or metallized glass (if glued the protection yourself).
• 💧 Moisture under the screen (even after a slight water intake).

⚠️ Warning: If you notice that the sensor stopped working after a phone drop or liquid hit, do not try to disassemble the device yourself - this can damage the flexible plumes.

6. When to contact the service: signs of hardware breakdown

If all of the above methods fail, it's likely a hardware problem, and here are the exact signs that the sensor needs repair or replacement:

• 🚫 The scanner is not defined by the system (in ADB There is no engineering menu or Sensor. ID).
• ⚡ The sensor works “once again” but after rebooting or impacting it starts to function – this is a sign of poor plume contact.
• 🔥 Artifacts appear on the screen around the scanning area (for optical sensors) - possibly damaged backlight module.
• 💧 The phone fell into the water or was exposed to high humidity - even after drying, corrosion could damage contacts.

The cost of repair depends on the model and type of sensor:

Before you bring your phone to the service, check:

• 📋 Warranty status: if the device is warranty, repairs can be free (but not always – for example, for mechanical damages).
• 🔧 Original parts: Ask the service if they use original Xiaomi modules or similar.
• ⏳ Repair time: Replacing the sensor usually takes 1-3 days, but rare models (such as the Black Shark) may require waiting.

⚠️ Warning: If you are asked to "reflash the sensor" instead of replacing it, it is a fraud. The fingerprint sensor is a hardware module and it cannot be "fixed" software. The only exception is the update of the sensor firmware through official Xiaomi software, but this is only done in authorized service centers.

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If the sensor stopped working after the MIUI update, try to roll back to the previous firmware version first. In 30% of cases, the problem is solved software.

FAQ: Frequent questions about the fingerprint scanner on Xiaomi