Why the screen does not turn off when talking on Xiaomi: the complete guide

When the display continues to burn during a phone conversation on a Xiaomi smartphone, it can cause serious discomfort. Instead of going out and locking, the screen remains active, which often leads to accidental tapping of the cheek or ear, switching to speakerphone or even resetting a call.

This behavior of the device indicates that the proximity sensor, which normally should detect the phone to the ear and turn off the backlight, is not working properly. In the MIUI operating shell, system services are responsible for this process, which can conflict with installed applications or get lost due to mechanical damage.

In this article, we will discuss the main causes of malfunction, from software bugs to physical defects, and provide step-by-step instructions for calibration and diagnosis. Understanding the nature of the problem will help you quickly return the functionality of the gadget without going to the service center.

The principle of operation of the proximity sensor in MIUI

The main element responsible for screen damping is an infrared sensor, usually located at the top of the front panel next to the speaker. In modern models of Redmi and Poco, this sensor is often hidden under glass, whereas in budget series it can be provided with a separate hole.

When you hold the phone to your head, the distance to the object is reduced, and the sensor detects a sharp change in readings. The operating system interprets this signal as a command to lock the display and turn off the touchscreen to avoid false positives. If the screen does not go out, then the signal is either not coming or is ignored by the software.

It is important to note that there are additional algorithms in the MIUI shell that analyze the position of the device in space. The accelerometer and gyroscope help the system to understand that the phone is near the ear, but the priority is always given to the readings of the optical sensor.

• 📱 The sensor is located at the top of the body, often hidden under a decorative panel.
• 📡 The signal is transmitted to the system process of the Phone to block the interface.
• 🔋 The energy consumption of the sensor is minimal, but it works in the background constantly.

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If you use a black-framed protective glass, make sure it doesn’t cover the sensor area, otherwise the screen will go out chaoticly or won’t go out at all.

Influence of protective glasses and accessories

One of the most common but common causes of incorrect operation is the wrong protective glass or film. Accessories manufacturers do not always take into account the exact location of the technological holes in specific models of Xiaomi smartphones. If the opaque zone (the opaque part) of the glass closes the sensor, infrared radiation cannot go out and come back.

The result is that the device thinks there's no obstruction in front of it, and it doesn't lock the screen, and sometimes the opposite is true: the glass has a black frame that's too thick, and it creates a permanent shadow over the sensor, which causes the screen to go out immediately after dialing, before the phone is even brought to the ear, and in both cases, you need to replace the accessory or reinstall it.

Also worth noting is the cases. Some models of book covers or bumpers with high sides can mechanically overlap the top of the device. Even if the sensor is not directly closed, the reflection from the inner surface of the case can distort the readings. Take off the case and see if this solved the locking problem.

⚠️ Warning: When you stick a new protective glass, carefully wipe the top of the screen. Dust or greasy spots in the sensor area can scatter IR rays, causing false positives.

Software failures and application conflicts

Often the problem is not hardware, but software. Android and MIUI can accumulate temporary files that cause conflicts in the work of system services, especially after a firmware update, when old settings may not interact properly with new code.

In addition, third-party applications that have access to telephony or run on top of other windows (e.g., blue filters, voice recorders, number detectors) can intercept the sensor. If such an application freezes or does not work correctly, it can block the command to turn off the screen. Check the list of recently installed programs and try to remove suspicious utilities.

Sometimes it helps to just restart the telephony service, you can use the engineering menu or just restart the device in safe mode, if in safe mode, where all third-party applications are disabled, the screen goes off correctly, then one of the software products you installed is the culprit.

adb shell dumpsys sensor | grep Proximity

This command in the ADB console allows the current status of the proximity sensor in real time, which is useful for advanced users when diagnosing software lags.

Engineering menu and sensor calibration

The most effective software solution is to calibrate the sensor through an engineering menu, which Xiaomi smartphones often access through a special code in the Phone app, which allows you to reset the accumulated errors and retrain the system to determine distances.

To enter the calibration mode, enter dialer code ##6484##. If the code does not work (on some global versions of firmware access is closed), you can download a special CIT or Engineering Mode application from the official GetApps store.

The calibration process is usually as follows: you cover the top of the screen with your hand (simulating a touch to your ear) and press the calibration button, then open the screen and press the button again. The system remembers the minimum and maximum light values. After the procedure is successfully completed (pass status), the phone is recommended to restart.

Diagnostics through hidden tests Xiaomi

The built-in CIT (Customer Interactive Test) is a powerful tool for testing hardware, which isolates the problem: if the sensor behaves correctly in the test (values vary from 0.0 to 5.0 when you put your hand), then it is good, and you need to look for the cause in the software.

When you pass the test, pay attention to the numbers. In the normal state (the phone is on the table), the value should be maximum (usually 5.0). When you close the sensor with your palm, the value should drop to 0.0. If the values "dance" or do not change at all, there is a possibility of hardware defect or oxidation of the contacts.

The table below shows the typical values and their interpretation in the diagnosis:

If the test shows a stable zero even without touching, it may be that the sensor is filled with liquid or the plume is damaged, and in such cases, the software methods are powerless.

Hardware malfunctions and physical impact

Physical damage is also not excluded: Falling a smartphone, even without visible cracks on the screen, can cause the proximity sensor plume to detach from the motherboard. In modern Xiaomi smartphones, the sensor is often integrated into the front camera plume or into a separate module under the display.

Moisture is another critical factor, and even a small amount of condensation in the area of a speaker can short-circuit the sensor's contacts or create a permanent shadow that blocks it, in which case the screen may either not go out or may not turn on after a conversation.

If calibration and resetting didn't work, and there are anomalies in the CIT test, you'll probably need to disassemble the device, check the connectors, clean the contacts with alcohol, and, if necessary, replace the sensor module itself. Self-repair is possible only with the experience and tools.

⚠️ Attention: Attempting to disassemble a smartphone under warranty will lead to loss of warranty obligations.In case of physical damage, contact the authorized service.

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If the software calibration and resetting of the settings did not give a result, and the CIT test shows a lack of sensor response, the problem is hardware in nature and requires a replacement of the sensor or plume.

FAQ: Frequently Asked Questions