Why does the phone screen of Xiaomi Redmi go off when dialing?

The situation of a phone screen suddenly turning off immediately after dialing or at the beginning of a conversation is familiar to many owners of Xiaomi and Redmi smartphones. This is not an accidental failure, but the result of an integrated security system designed to prevent accidental tapping of the cheek or ear. However, when the display stops lighting up even after the device is removed from the face, this becomes a serious problem, preventing the completion of the call or dialing an additional number.

The main culprit for this behavior is often the proximity sensor located at the top of the body next to the speaker, which constantly monitors the distance to the object and signals the system to turn off the backlight. In Xiaomi brand devices, the implementation of this mechanism has its own features, which sometimes lead to false positives due to software errors or physical obstacles.

Understanding the way the node works makes it easier to find the cause of the malfunction. The touch layer stops responding to touch precisely because the system thinks the phone is pressed against the ear. If the screen goes out for no apparent reason or doesn't turn back on, then the calibration process is disrupted or the sensor is blocked. In this article, we will discuss all possible causes and ways to eliminate them.

The principle of the sensor approach in smartphones Xiaomi

The technology is based on an infrared emitter and a receiver that work in pairs. When you hold the phone to your head, the infrared beam bounces off the surface and returns to the receiver, which is recorded as an "object close" event. On Redmi Note devices and other series, this process takes a fraction of a second. Android receives a signal and blocks the touchscreen so that the cheek does not reset the call or turn on the hold.

However, in modern models that use a virtual sensor, relying on software algorithms rather than a dedicated hardware sensor, the error rate increases. The software algorithm analyzes data from the accelerometer and gyroscope, trying to guess the position of the phone. If at this point there is a failure in the operation of the MIUI or HyperOS operating system, the screen can go out even if the phone is lying on the table.

The physical location of the element also plays a role. In classic smartphones, it is in a narrow strip above the display. In models with a cutout or hole in the screen (punch-hole), the sensor can be hidden under the matrix, which is where calibration becomes critical, because the layer of the display can distort the sensor readings.

⚠️ Warning: If the screen goes out when you just hold the phone in your hand a distance away 10-15 see from the face, this is a clear sign of a sensor malfunction or the need for urgent calibration.

It is important to note that the sensor requires minimal energy, but its incorrect operation can lead to battery discharge, since the processor constantly polls the state of the sensor. System interrupts can "hang" to prevent the screen from turning back on.

Influence of protective glasses, films and covers

One of the most common but common reasons why the screen goes out when dialing is to install the security film or glass incorrectly. Many users, wanting to protect the display Xiaomi Redmi, seal the top of the case, blocking access to the IR emitter to the outside world, even a translucent film can interfere with the infrared spectrum.

If the security glass has a black frame around the perimeter, it can completely block the sensor window. In this case, the sensor constantly "sees" the obstacle and thinks that the phone is pressed against the head. The thickness of the glass also matters: too thick glasses (more than 0.5 mm) can reduce the sensitivity of the sensor, making it unstable.

Cases with high sides or the wrong shape of the speaker cutout can also be a cause. When dialing, you take the phone in your hand, and your finger or edge of the case can accidentally overlap the sensor's area of operation, especially for models with a side-button on, where the design of the case requires accurate fitting of accessories.

To test this theory, you just need to remove the protective coating and cover, and then make a test call, and if the problem disappeared, then it was a physical blocking of the infrared beam, in which case it is recommended to replace the accessory with a better one, with the right cutouts.

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When buying a security glass for Xiaomi, pay attention to the presence of a cutout at the top or a transparent area above the speaker.

MIUI software failures and system settings

The MIUI shell and the new HyperOS have many features that can conflict with each other. Sometimes the phone screen goes out due to a bug in the Phone or Contacts system application, which can occur after a firmware update, when old configuration files conflict with new algorithms.

It's also worth checking the special access settings. In some versions of the shell, there's a "Mode in your pocket" feature that uses a proximity sensor to lock the screen when the phone is in the bag. If the sensitivity of this feature is set to maximum, the screen can go out with any movement of the hand near the top of the case.

Failures in the Android framework can also cause the sensor signal to not be processed correctly, and the system forgets to turn the screen back on after the call is complete, in which case cleaning the cache of system applications or resetting the settings to factory ones helps, but it is worth trying simpler methods before that.

Often, the problem is solved by updating the Google Play Services app or the dialer itself. Go to Settings → Apps → All apps, find Phone and check for updates or try to clear the data. This will not delete your contacts, but reset your call settings.

Calibration methods for the proximity sensor

If physical obstacles are eliminated and the screen continues to go out, you need to calibrate the sensor, a software procedure that trains the phone to understand what is near and what is far. In Xiaomi and Redmi smartphones, this process is built into the engineering menu.

To enter the test mode, you need to dial a special code in the call app. Once you enter the command, the CIT menu will open, where you can check the operation of all the sensors. Find the "Proximity Sensor" item and follow the instructions on the screen: usually you need to close the top of the phone with your hand and then remove it.

In some cases, standard calibration through the engineering menu does not help, and requires the use of third-party applications from Google Play, such as "Proximity Sensor Reset/Fix." These utilities force overwrite the sensor sensitivity values, but be careful and download only proven programs with high ratings.

⚠️ Note: Do not calibrate if there is a black-framed protective film on the phone screen, the result will be incorrect, and the screen may go out with only this film in the future.

After successful calibration, be sure to restart the device. System restart is necessary to apply new sensitivity parameters. If after the reboot the problem persists, it is possible that the sensor is physically damaged or the plume inside the housing has moved away.

Conflict of applications and third-party software

User-installed applications can also interfere with system functions, especially with memory cleaners, accelerators and call management applications, which can take control of the proximity sensor and not give it back to the system.

To identify the culprit, try running your phone in Safe Mode, which only downloads system applications, and if in Safe Mode the screen stopped going off spontaneously, then there's a problem in one of the apps you installed. Start removing the newly installed software.

Special attention should be paid to applications for recording calls, some of which use a proximity sensor to detect the beginning of a conversation to start recording, and conflict between a standard caller and a third-party recorder can lead to a lockdown of the screen.

Also check access rights. Go to Settings → Apps → Permissions → Other permissions. Make sure that suspicious apps don't have "Map on Other Windows" or sensor access rights. Limiting those rights can fix the problem.

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If the problem disappears in safe mode, the third-party application is to blame, and the elimination method will help find it faster than a complete reinstallation of the system.

Hardware malfunctions and repairs

When software methods don't work, you have to look at hardware problems, and the proximity sensor is a physical component that can fail, and it can be a plume break, the contact oxidation after moisture hits, or just a manufacturing defect.

In smartphones with a cut-out in the screen (under-display sensor) often unplugs the sensor itself from the inside of the display, in which case it "sees" only the insides of the case and thinks that the phone is permanently closed, repair in this case requires disassembling the device and sticking the sensor in place or replacing it.

It's also worth checking the status of the plume of the display, because if you fall down, the connector could move away, if you have repair skills, you can gently press the plume near the top module, but you should trust the service center to do this so that you don't damage the matrix.

In some cases, a temporary solution helps: disabling the proximity sensor through the engineering menu (if your firmware version allows it to do so), the screen will burn constantly during the conversation, which is inconvenient, but will allow you to use the phone until repaired, but remember that this will increase the risk of accidental pressing.