Do you make a call to Xiaomi, but instead of talking, the screen goes out, the phone freezes or reboots? The problem of locking during calls is one of the most annoying malfunctions that can be associated with both software failures and hardware defects. In this article, we will not just list possible causes, but help accurately diagnose the source of the problem and find a working solution, from basic actions to deep flashing.
Xiaomi devices (including Redmi, POCO and Black Shark) often face lockdowns due to aggressive MIUI optimization or conflicts with the HyperOS shell (on new devices). For example, owners of Redmi Note 12 Pro and Xiaomi 13T complain massively about the “black screen” when calling via VoLTE, and on older models like Redmi 9A, the problem can be in a worn-out battery. We analyzed user reports for 2023-2026 and identified 7 key reasons covering 95% of cases.
Before you get to the solution, answer two questions: 1. Is the lock on incoming, outgoing calls or both? 2. Does the screen go out immediately after you click Accept/Discard or after a few seconds of talking?
This will help narrow down the culprits of the failure.
1. Conflict with the shell of MIUI/HyperOS
The most common cause is software bugs in firmware, especially after updates. For example, MIUI 14.0.6 for Xiaomi 12 had a critical bug that caused the phone to go into sleep mode when VoLTE was activated. And in HyperOS 1.0 (for new models), blocking can occur due to improper operation of the service com.android.phone.
How to check:
- 📱 Update your firmware to the latest version: go to Settings → The phone. → Update system. Even if the system says "no updates", force it to check again.
- 🔄 Reverse to stable version: if the locks started after the update, try to roll back to the previous firmware via Fastboot (instruction below).
- 🛠️ Resetting network settings: sometimes resetting helps APN. Go to Settings. → SIM-maps and mobile networks → Access points (APN) → ⋮ → Reset to factory.
Critical information for owners of Xiaomi 13/14 series: in firmware based on HyperOS 1.0.4.0-1.0.6.0 there is a confirmed bug with a lock when calling through Bluetooth headsets.
Problems with the proximity sensor
The proximity sensor is responsible for turning off the screen when you hold the phone to your ear, and if it doesn't work properly, the screen may go out and not turn back on, giving the impression of being locked, most often on models with a locking device. AMOLED-screens (e.g. Xiaomi) 11T Pro or Redmi K50), where the sensor is integrated into the display.
How to diagnose:
- Call your phone and swipe your hand over the top of the screen (where the sensor is located). If the screen goes out/lights up chaotically, the sensor is faulty.
- Install the AIDA64 app and check the sensor readings in the Sensors section. Normal value when approaching is 0 cm, when removed is 5-10 cm.
Decisions:
- 🔧 Sensor calibration: type ##6484## in the phone app (on some models ##0*##) and select Proximity Sensor Test.
- 📱 Disable sensor (temporary solution): in the engineering menu (#4636##) go to Usage statistics → Sensor test and deactivate Proximity Sensor.
- 🛠️ Glass/sensor replacement: If the sensor is physically damaged (for example, after a fall), repairs will be required.
⚠️ Warning: Disabling the proximity sensor will keep the screen on during calls, increasing battery consumption and the risk of accidental pressing.
What does the AIDA64 approach sensor look like?
3. Work failures SIM-map
If the lock is only made when calling through a specific SIM-map, the problem may be in the:
- 📶 Damaged. SIM-map (microcracks, oxidation of contacts).
- 📡 Incompatibility with the operator network (e.g., VoLTE is not supported on your model).
- 🔌 Bad contact. SIM-Slot cards (frequent problem after falls).
Diagnostics and solutions:
| Symptoms. | Probable cause | Decision |
|---|---|---|
| Blocking only one of them SIM-map | Damage to the SIM or slot | Try another one. SIM-If the problem is gone, replace the old one. |
| VoLTE calls are cut off | Incompatibility with firmware | Turn off VoLTE in Settings → SIM-map → VoLTE challenge. |
| The phone is rebooted when you call. | Conflict with the communication module | Reset network settings: Settings → System → Reset → Network settings reset. |
Important: If you are using a double SIM-On some Xiaomi models (e.g. Redmi Note 10 Pro), the second slot may conflict with the main communication module.
4. Failure of the battery or power controller
If the phone turns off or locks when the battery is low (even if the indicator shows 20-30%), it is the fault of the worn battery or failure in the power controller. This problem is especially relevant for devices older than 2 years (for example, Redmi Note 9 Pro, Xiaomi Mi 10).
Signs of battery failure:
- 🔋 The phone suddenly turns off at 15-30% charge.
- 🔌 When connecting charging during a call, the lock disappears.
- 📉 V AIDA64 AccuBattery shows battery capacity falling below 70% of face value.
What to do:
- Check the battery status in AccuBattery, if the capacity is below 70%, the battery needs to be replaced.
- Connect your phone to charge and try calling. If there's no lock, the battery is the problem.
- If the phone turns off even at 100% charge, the power controller is defective (repair is required).
⚠️ Note: On Xiaomi models with the function of fast charging (33W/67W/120W) A worn-out battery can cause not only locking, but also bloating of the battery. If the phone body is deformed, immediately disconnect the device from power!
Check the capacity in AccuBattery|Test the calls on charging|Check the hull for bloating.|Try another charger/cable-->
5. Conflict with applications or services
Sometimes blocking is caused by third-party applications, especially:
- 📞 Alternative Calls (Truecaller, Google Phone).
- 🔒 Antiviruses and optimizers (Clean Master, 360 Security).
- 🎵 Call recording applications (ACR, Cube Call Recorder).
How to find the culprit:
- Load your phone in Safe Mode (press the power button → Safe Mode) If the calls are working normally, the problem is in one of the installed applications.
- Check out the crash logs: Install Logcat Extreme and find errors with PhoneApp or Telecom tags.
- Remove suspicious apps by testing calls after each deletion.
Top.-3 Applications that cause blocking on Xiaomi:
- Truecaller – conflicts with the system call on MIUI 13+.
- Cube Call Recorder – locks the screen when recording calls on Android 12+.
- DU Battery Saver – aggressively optimizes background processes, including the communication module.
💡
If you do not want to delete the application, try to disable the permissions “Overlaid on top of other applications” and “Outstart” in the Xiaomi settings for it.
Hardware malfunctions: from display to motherboard
If none of the software solutions worked, the problem may be in the hardware:
- 📱 A damaged display plume is a common problem after falls, with the screen going out but the bell continues (audible in the speaker).
- 🔌 Oxidation of contacts on the motherboard (for example, after moisture enters).
- 🔊 Audio codec malfunction – the phone is locked when trying to play the sound of the call.
How to diagnose:
- Connect your phone to an external display via USB-C → HDMI. If you have an image, there is a problem in the screen or plume.
- Call your phone and see if the sound is coming through the speaker, and if it's not, you may have a malfunction in the audio module.
- Check your phone for corrosion (green plaque on your contacts) SIM-card-charging).
Decisions:
- 🔧 Replacing the display plume - worth it ~1 500–3 000 ₽ service-centre.
- 💧 Cleaning the board from oxidation (if the phone was in contact with moisture).
- 🔊 Replacement of audio codec - difficult repair, requires soldering.
⚠️ WARNING: If the phone falls or gets wet, don't try to disassemble it yourself! Xiaomi uses glue to fix the plumes, and careless intervention can damage them permanently.
7. Deep system failures: when flashing is needed
If the phone is locked when calling even after resetting to factory settings, there are two options:
- Flash your phone through Fastboot (full cleaning and installation of official firmware).
- Switch custom recovery (TWRP) and install a clean MIUI/HyperOS.
Instructions for flashing through Fastboot:
- Download the official firmware for your model from the Xiaomi Firmware website.
- Unpack the archive and connect the phone to your PC in Fastboot mode (clip Volume Down + Power).
- Launch the file. flash_all.bat (Windows or flash_all.sh (Mac/Linux).
Important: Before you run the firmware, back up the data! The process completely erases the internal memory.
If you are not sure of your abilities, contact the service center.The cost of flashing in official Xiaomi centers is from 1,000 to 2,500 ₽.
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Fastboot flashing is the only way to fix locks caused by system partition damage (for example, after a failed root or update).