Why Xiaomi screen is blocked when you call: a full analysis of the causes and solutions

Introduction: The Problem Millions Face

You call a friend, you bring Xiaomi to your ear, and suddenly the screen goes out, locks or stops responding to touch. The call continues, but you can not control it: you can not turn on speaker, switch to speaker or complete the call. The situation is familiar? According to service centers, this problem is addressed by the owners of one in five Xiaomi smartphones, regardless of the model — whether it is a budget Redmi Note 12 or flagship Xiaomi 14 Ultra.

The reasons for this behavior are diverse, from software failures in the MIUI shell to physical damage to sensors. In this article, we will examine all possible causes of a screen lock during a call, learn how to diagnose the problem and fix it without contacting the service. We will focus on nuances that are not written about in forums - for example, how the impact of cases on the operation of the proximity sensor or why after the MIUI update the problem may worsen.

Important: If the screen doesn’t just go out, but shuts down completely and doesn’t respond to the buttons (even after the call is over), it can indicate a critical board malfunction, in which case self-repair can exacerbate the problem.

1. Approximation sensor: the main reason for blocking

In 80 percent of cases, the culprit is the proximity sensor, which is responsible for turning off the screen when the phone is held to the ear, and if it doesn't work properly, the screen may go out too early, not turn back on, or lock completely, and is usually located at the top of the screen, next to the speaker.

How to check his work:

• 🔍 Testing through the engineering menu: enter the phone app code ##6484## (older versions MIUI) or #4636##, then select Sensor Test → Proximity Sensor. Put your hand to the sensor, the value should change from 5.0 cm to 0.0 cm.
• 📱 Manual check: during the call, try to close the sensor with your finger - the screen should go out. Remove your finger - the screen should turn on.
• 🛠️ Visual inspection: often the sensor gets contaminated or covered with film/glass, wipe it with a soft napkin soaked in alcohol.

If the sensor does not respond or shows incorrect values, the problem may be:

• 🧹 Pollution (dust, potowows).
• 🔧 Damage to the plume (for example, after a phone drop).
• 🔄 Calibration failure (solved by resetting sensor settings).

⚠️ Warning: Don't try to disassemble the phone to clean the sensor without experience! In Xiaomi models, the proximity sensor plume is often combined with the front camera plume - it is easy to damage.

2. Software failures: MIUI, updates and bugs

The MIUI shell is known for its surprises, and locking the screen during a call is one of them, most often the problem occurs after:

• 🔄 Updates to MIUI (especially in beta versions).
• 📱 Install third-party firmware (e.g., Xiaomi.EU or LineageOS).
• 🗑️ Clear cache through Settings → Memory.

How to diagnose a software failure:

1. Check if the problem appears in safe mode (press the power button → Safe Mode) and if it works, it's the third-party app's fault.
2. Reverse to the previous version of MIUI (if the problem appeared after the update). To do this, download the firmware from the official website and swipe through Settings → About phone → System Update → Three points → Select a firmware file.

Critical information: In MIUI 14 and later, a screen locking bug when calling can be associated with optimizing power consumption. Turn off Adaptive Brightness in Settings → Display → Adaptive Brightness – this sometimes helps.

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If the problem has occurred after the update, but you don’t want to roll back, try resetting the network settings: Settings → SIM- Maps and mobile networks → Resetting the network settings. This often helps with communication bugs.

3. Influence of covers, glass and film

Few people think about it, but cases and protective glasses can block the proximity sensor, causing false positives, especially for models with a monobrav (for example, the Redmi Note 11 Pro), where the sensor is located in a thin frame above the screen.

What to check:

• 📏 Case thickness: If it covers the top of the phone (where the sensor is located), try calling without the case.
• 🔮 Transparency of glass: Some of the protective glass has a metallized layer that shields the sensor signal. Try removing the glass and testing it.
• 🧲 Magnetic holders: If you use a magnetic case or holder for a machine, it can affect the sensor.

Test: Call someone, then alternately:

1. Remove the cover and check the screen reaction.
2. Remove the protective glass (if any).
3. Try calling while holding your phone in different positions (for example, from a different angle).

⚠️ Warning: In Xiaomi Poco F5 and Redmi K60 models, the proximity sensor is combined with the light sensor. If after removing the case, the problem persists, but the screen begins to behave nervously (spontaneously change brightness), this is a sign of sensor damage.

4. App conflict: who is to blame?

Third-party apps can intercept the screen during a call, most often to blame:

• 🔒 Screen locking applications (e.g. AppLock, Smart AppLock).
• 🎵 Music players with auto-disconnect screen (e.g., Poweramp).
• 🔋 Battery optimizers (e.g. Greenify, AccuBattery).
• 📞 Alternative calls (e.g. Truecaller, Drupe).

How to find the culprit:

1. Run your phone in Safe Mode (press the power button → Safe Mode) If the problem has disappeared, the third-party app is to blame.
2. Turn off applications with Overlay rights on top of other applications (Settings → Applications → Permissions → Overlay).
3. Check the battery saving settings for the Phone app (Settings → Battery → Saving Charge → Applications). If there is a restriction, remove it.

Pay special attention to applications that request permissions:

• 📱 Call management
• 🔍 Reading call logs
• 🛠️ Changes to system settings

Remove newly installed applications|Disable battery optimization for "Phone"|Checking the imposition permits|Testing in safe mode-->

5. Hardware malfunctions: when without service can not do

If the software methods didn't work, the problem could be the hardware.

• 🔌 Damage to the proximity sensor plume (often after a drop or repair of the screen).
• 🔋 Battery bloating that presses the motherboard and causes sensor malfunctions.
• 💧 Moisture infestation (even if the phone hasn’t sunk, condensation can oxidize contacts).
• 🔧 Display control chip malfunction (in this case, the screen can be locked not only during the call, but also during other loads).

Signs of hardware malfunction:

• 🔄 The screen is locked even without a call (e.g., while watching a video).
• 🔥 The phone overheats at the top (where the sensor is located).
• 📵 The proximity sensor is not working at all (reacts to nothing).
• 🔌 Once the charging is connected, the problem is amplified.

What you can do on your own:

1. Check the phone for battery bloating, put it on a flat surface and spin it, and if it's walking, the battery is swelling.
2. Check the charger connector for oxidation (green or white coating).
3. If the phone falls, check if the screen is moving away from the case (this may indicate damage to the plumes).

⚠️ Warning: If the phone is locked and reboots or shuts down, it may be a sign of a processor malfunction (e.g., in the Snapdragon 8 Gen 1/2 models known for overheating problems).

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If the screen is locked and the phone vibrates or emits audible signals (like when charging), it is almost guaranteed to be a hardware problem.

6. Energy saving and optimization settings

Aggressive power saving settings in Xiaomi can block sensors during a call, especially for models with a small battery (such as the Xiaomi 13 Lite or Redmi 10C), where MIUI by default limits background activity.

What to check:

• 🔋 Power saving mode: turn it off in Settings → Battery → Power saving mode.
• ⚡ Battery Optimization for Phone: Go to Settings → Battery → Power Saving → Applications and select the No Limits option for the Phone app.
• 🔄 Automatically turn off screen: in Settings → Display → Sleep mode set the value Never (for the test).
• 🛠️ Background optimization MIUI: disable it in Settings → Permissions → Autorun for the Phone application.

If the problem occurs after the MIUI update, try resetting the power saving settings:

1. Go to Settings → Battery → Three dots (menu) → Reset the battery settings.
2. Confirm the reset and restart the phone.
3. Test the call.

In some cases, turning off the Adaptive Battery feature (Settings → Battery → Adaptive Battery) helps.This feature analyzes your habits and may misinterpret phone use during a call as "simple."

7. Firmware and custom ROM: risks and solutions

If you use custom firmware (e.g. Xiaomi.EU, LineageOS, Pixel Experience), the screen lock problem may be related to:

• 🔧 Incorrectly assembled core (no proximity sensor support).
• 📱 Missing drivers for your model.
• 🔄 Conflict with Magisk modules (e.g., battery optimisation modules).

How to diagnose:

1. Check the error log through the adb logcat during the call. Look for lines with proximity or sensor.
2. Install the original firmware via Fastboot and check if the problem persists.
3. If you use Magisk, disable all modules and test the call.

Solutions for custom firmware:

• 🔄 Firmware with full data cleanup (wipe data, cache, dalvik).
• 📥 Install a dedicated core for your model (e.g., FrancoKernel for Poco F3).
• 🛠️ Manually calibrate the sensor through the engineering menu (code ##6484###).

Example of a command to test the sensor via adb:

adb shell dumpsys sensorservice

⚠️ Warning: On some custom firmware, the proximity sensor may be running backwards -- the screen goes off when you remove the phone from your ear, and turns on when you bring it up. This is only treated by flashing it.

FAQ: Frequent questions about screen locking on Xiaomi