The situation when the screen of Xiaomi suddenly goes out at the beginning of a conversation and stops responding to touch is one of the most common complaints of smartphone owners of this brand: the user tries to put the phone down or turn on speakerphone, but the display remains black, turning the device into a useless piece of plastic. This is not just an annoying bug, but the result of the work of specific algorithms of the MIUI or HyperOS system, which are designed to save battery and prevent accidental clicks of the cheek.
The root of the problem is most often a proximity sensor that misinterprets the phone's position in space. The touch screen is blocked by the security system, thinking that the smartphone is pressed to your ear, even if you hold it in front of your eyes. Understanding the mechanics of this process is the first step to successfully solving a problem, whether it's a software glitch or a physical interference.
In this article, we will take a look at all possible causes, from banal protective film to complex system process conflicts. You will learn how to properly calibrate sensors, disable unnecessary energy saving functions, and use hidden engineering menus for deep diagnostics. Xiaomi smartphones have a flexible system of settings, and often the solution lies in one non-obvious switch.
Mechanics of the approximation sensor in MIUI
The main culprit behind the lock is the proximity sensor, which is a small module, usually located on the top of the case next to the speaker or built directly into the screen (in expensive models), constantly measures the distance to the object. When you bring the phone to your face, the sensor detects the reflection of infrared radiation and signals the system to turn off the display to save energy and prevent false cheek touches.
The problem arises when the sensor receives a false positive signal, which can be due to pollution, body design, or calibration software errors. The Android system in the MIUI shell reacts very aggressively to such signals, instantly blocking the touchscreen, making it impossible to control the interface during the call.
⚠️ If you notice that the screen goes out even when the phone is lying on the table and no one is looking at it, this is a sure sign that the sensor is stuck or closed by a foreign object, and not just a software failure.
It's important to understand that current models use a virtual sensor that uses artificial intelligence algorithms to analyze data from an accelerometer and a gyroscope, and a mistake in how these algorithms work can cause the phone to "think" it's in your pocket or ear, blocking the screen menu for no apparent reason.
How to check the sensor without a call?
Influence of accessories and physical obstacles
The most common but often ignored reason is the improper installation of protective glasses or films. Many users buy cheap accessories that have a solid black coating at the top, completely blocking the operation of the infrared sensor, even a microscopic speck of dust or a greasy spot in this area can distort the sensor readings.
High-sided cases can also create shadow over the sensor, especially if they are not matched to the model or have thick walls. The mechanical pressure of the case on the upper end can slightly deform components, which leads to malfunctions in the touch layer.
To solve this problem, carefully examine the top of the smartphone when the screen is off. Remove all contamination with an alcohol napkin. If you use a black-framed protective glass, make sure that the notch under the speaker matches the actual location of the sensors. In some cases, removing the case to test the hypothesis helps.
Software calibration of sensors through the engineering menu
If physical obstacles are eliminated, software calibration is required. In Xiaomi, Redmi and Poco smartphones, there is a hidden CIT engineering menu that allows you to test and configure all hardware modules, and this is the most effective way to “train” the system to respond correctly to the position of the phone.
To enter the diagnostics menu, open the Phone app and dial the combination ##6484##. In the list that opens, look for Proximity sensor. Follow the instructions on the screen: you usually need to close and open the top of the screen to record the minimum and maximum values.
☑️ Algorithm of sensor calibration
After a successful calibration, restart the device. It often happens that after a firmware update, the old calibration data conflicts with the new drivers, and a simple re-tuning brings the touchscreen back to life. If the calibration is successful, but the problem persists, it is worth checking for system updates.
Power saving settings and screen lock
MIUI is famous for its aggressive power optimization. Pocket mode or Pocket mode often causes the screen to go out and not respond, the algorithm believes the phone is in a dark confined space, and locks the display to prevent random action.
To disable this feature, go to Settings → Screen Lock. Find “Mode in your pocket” and turn it off. It’s also worth checking the Battery Savings settings for the Phone app. If the system is allowed to restrict background activity too much, it may not properly process sensor signals during a conversation.
| Setting up | Location on the menu | Recommended action |
|---|---|---|
| Pocket mode. | Settings → Screen locking | Shut down. |
| Approximation sensor | CIT Menu → Proximity | Calibrate. |
| Saving energy | Settings → Battery | No restrictions on the phone |
⚠️ Warning: Turning off Pocket mode can lead to accidental taps if you carry your phone in a tight pocket without locking.Use this setting with caution.
Application conflicts and third-party software
Third-party calling apps like Truecaller, Viber, or WhatsApp can intercept sensor control. If you have multiple apps that have access to the microphone and phone, there may be a resource conflict where the system interface stops receiving correct status data on the proximity sensor.
Try resetting the Phone and Contacts app settings. Go to Settings → Apps → All apps, find a standard dialer, and select Clear → All data. This will return the call settings to factory settings, eliminating software configuration errors.
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Use the standard Phone app from Google or Xiaomi instead of third-party counterparts if the screen problem only occurs in certain messengers or Dialers.
It’s also worth checking whether Do Not Disturb or Night Mode is enabled with special activation rules, and sometimes script automation (Mi Automation) can block the screen when an incoming call is made if the rules specify a time or location condition.
Hardware malfunctions and repairs
If software methods don't work, there's a high probability of hardware failure. In Xiaomi smartphones, the proximity sensor plume is often combined with the bottom microphone plume or volume buttons, and when it falls or gets moisture, this plume can move away from the motherboard connector.
In such cases, disassembly of the device and reconnection of the plume are required. If the sensor is built into the screen (as in some Mi series models or flagships), then the malfunction may indicate damage to the display module itself.
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If the calibration in CIT-The menu shows constant zeros or maximum values regardless of the position of the hand, the sensor is physically defective and requires replacement.
A temporary solution may be to use a hands-free or Bluetooth headset, since in this mode the proximity sensor is often ignored by the system and the screen remains on.