When an incoming call arrives, the screen of a Xiaomi smartphone is black, causing the user to panic, you can't see who is calling, and you can't answer the call, which in emergency cases can be a serious problem, most often this failure is due to the malfunction of the proximity sensor, which mistakenly believes that the phone is near your ear, and locks the display.
However, the reasons may lie not only in the hardware, but also in the software conflicts of the MIUI shell or HyperOS. The system may have been updated, and new settings for energy saving or application resolutions began to block the standard behavior of the interface, and it is worth considering the influence of security glasses, which sometimes overlap the touch element.
In this article, we will take a look at all possible scenarios, from simple software errors to the need to calibrate the sensor, how to make a self-diagnosis and what hidden settings can affect the screen during a call, the main thing is to act consistently to eliminate factor by factor.
Approximation sensor: calibration and serviceability check
The most likely culprit for keeping the screen from lighting up is the proximity sensor, which is a small module on top of the smartphone, next to the speaker, which is designed to turn off the display when you bring the phone to your ear to avoid accidental cheek pressing, and if the sensor is stuck or contaminated, the system will think that the phone is in your ear all the time.
Redmi and Poco smartphones often use a virtual sensor that works on the front camera, making it more sensitive to software failures. A physical sensor that runs on infrared radiation can simply get clogged with dust or be covered with thick protective glass. Both require initial diagnosis through an engineering menu.
⚠️ Warning: Before calibrating, be sure to wipe the top of the screen with a soft cloth.Even the presence of microscopic dust or a greasy spot above the speaker can give false sensor readings.
To check for health, use the built-in engineering test. Open the Phone app and enter the code ##6484##. In the CIT menu, find the item "Proximity sensor." Hold your palm to the top of the screen and remove it: the indicator should change the value from "Near" (close) to "Far" (far). If there is no reaction, the problem is hardware or requires reset.
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If the sensor does not respond in the CIT test, try to gently warm the upper part of the body with a hairdryer at a minimum temperature for 30 seconds - sometimes this helps to "revive" the stuck sensor.
System settings and application permissions
MIUI is known for its aggressive power-saving system, which can force background processes, including telephony service, to close. If the Phone or Contacts app has been revoked, the call interface may not be activated before the system locks the screen, often after major Android updates.
You need to manually check autorun and access rights. Go to Settings → Applications → All apps. Find the list "Phone" (or "Services and Feedback" if you use Google calls). Make sure that the "Outstart" and "Master on top of other applications" are enabled. Without the last resolution, the screen can remain black.
Also worth paying attention to is the design theme: Some third-party themes downloaded from Themes may not be optimized for your Android version and contain errors in the lock screen code, in which case the call interface simply does not render.
- 🔍 Check to see if Do Not Disturb or On-Plane modes are enabled, which may block visual notifications.
- 🔍 Make sure the screen settings have disabled the “Mode in your pocket” function if it is not working properly.
- 🔍 Reset the theme settings to standard ("Classic" or "Free") to eliminate interface conflict.
Third-party application conflicts and junk files
Installing memory cleaners, antiviruses, or alternative calls can lead to system process conflicts, for example, if you use Truecaller or a similar number detector, it can intercept the call before the system shell. If there is an error in the application code, the screen may not catch fire, although the sound of the call will go.
The accumulated cache also plays a negative role. Over time, temporary files accumulate in the system folders, which can slow down the interface response. If the processor is busy processing background tasks, the command to turn on the screen may simply get lost in the queue.
⚠️ Warning: Don’t use questionable accelerator apps from Play Market. Xiaomi’s built-in optimizer is enough, and third-party software often creates more problems than it solves.
Try to remove newly installed apps, especially those that have access to contacts or a microphone. If the problem disappears after you delete a particular application, then the conflict was in it, and it is also useful to clear the cache of the Phone application itself through the settings menu.
How do I clear the cache of the calls?
Hardware causes and the impact of accessories
The physical impact on the device cannot be ruled out, because the fall of the smartphone could lead to detachment of the display plume or the proximity sensor itself inside the case, in which case the screen may not light up not only when calling, but also work with artifacts in other situations.
Security glass is a frequent culprit for sensor problems. If the glass is curved, has a black frame that covers the touch zone, or is simply too thick, it blocks the IR radiation of the sensor, the system constantly receives the "object near" signal and keeps the screen off.
The table below shows the main signs of hardware and software problems:
| Symptoms. | Probable cause | Method of decision |
|---|---|---|
| The screen is black, but the vibration is there. | Proximation sensor closed/drenched | Remove the glass, clean the speaker |
| The screen flashes when the bell rings | Conflict of theme or the SO | Reset theme, system update |
| Black Screen After Fall | Display plume departure | Repairs at the service centre |
| It doesn't work just in a case. | Case override sensor | Replace the cover with the cut-out model |
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If removing the protective glass and cover did not help, the probability of hardware failure of the sensor is more than 80%.
Resetting and calibration through the engineering menu
If simple methods don’t work, you need to program reset the sensor settings. In some Xiaomi models, a hidden calibration function is available. To do this, you need to find the item “Proximity sensor” in the CIT menu (call # #6484##), put the phone on a flat surface and press the “Calibration” button.
Once the calibration is successful, the phone vibrates and the test is considered passed. If the calibration does not pass (Fail status), this may indicate a malfunction of the module, in which case only a full data reset (Hard Reset), but make sure to make a backup before doing this.
☑️ Algorithm of actions in case of failure
Remember, a complete reset will delete all data. Use this method only as a last resort when software conflicts are ruled out and calibration has failed. Often, after resetting and clean installation of a system without third-party software, the problem resolves itself.
What to do if nothing helps
In rare cases, the problem lies in the display module itself, where if the screen stops lighting up at all or there are stripes on it, it is a physical breakdown of the matrix or the power controller, and the software methods are already powerless.
It’s also worth checking for system updates. Xiaomi engineers regularly release patches that fix sensor errors. Go to Settings → About phone and click on the MIUI version to check for updates.
If the phone is warranty-free, don't try to disassemble it yourself. Any trace of an autopsy will result in a denial of warranty service. Contact an authorized service center for professional diagnostics.