When a smartphone screen continues to burn, rather than go out, when it is brought to the ear, during a phone call, it is a common problem for users of MIUI-based devices. This not only causes occasional cheekstrokes, but also significantly consumes battery power, turning a long conversation into a battle with the sensor. The main reason lies in the incorrect operation of the proximity sensor, which is physically or programmatically unable to detect the location of an object next to the display.
In most cases, the problem is solved by software methods, such as calibrating the engineering menu or resetting the system, but sometimes the culprit is a protective glass or case that covers the upper part of the case. Understanding the principle of operation of this module will help to quickly diagnose the malfunction and choose the right algorithm for restoring normal operation of Xiaomi, Redmi or POCO.
It is worth noting that modern smartphones use a combination of optical and ultrasonic sensors, the sensitivity of which can be lost after a device drops or an operating system update. If your screen stops blocking during a call, do not rush to carry the gadget into the service - often it is enough to perform a simple sequence of actions described below to return functionality.
Principle of operation of the proximity sensor and causes of failures
The proximity sensor is an infrared emitter and receiver located at the top of the display, usually next to the speaker. In normal mode, it constantly emits invisible radiation and analyzes the reflected signal. When you hold the phone to your ear, the reflection is interrupted or changed, and the system receives a command. PROXIMITY_EVENT The problem with this signal is that the screen continues to glow, ignoring the position of the device.
One common cause of malfunction is a software conflict that occurs after updating the MIUI firmware or installing third-party applications that intercept call management. The system may “forget” calibration data or misinterpret sensor readings due to driver errors, in which case even a physically fit module will not be able to perform its function without forced resetting.
It's also important to consider the effects of external factors, such as black-framed protective films that can overlap the sensor's workspace, or the banal dirt in the speaker area. It's critical to check if the area is glued above the speaker, since even a thin layer of glue or dust can scatter the infrared beam and knock down the readings.
⚠️ Warning: If you have recently changed the display or body, make sure the proximity sensor plume is tightly connected and not squeezed.Improper assembly is a common cause of problems after repairs.
Basic inspection and cleaning of the sensor area
Before we go into complex engineering manipulations, we need to eliminate the banal physical obstacles: owners of models with a neckline ("bangs") or a hole in the screen should carefully examine the top frame. Often, the protective glass, offset, completely blocks the light from the receiver, which makes the phone "think" that it is always in the hand or on the table.
Cleaning should be done with a soft, dry microfiber, paying special attention to the area around the speaker. If you use a case with high sides, try to remove it and make a test call — perhaps thick plastic interferes with the correct operation of the sensor, in some cases, helps temporarily remove the protective glass to test the hypothesis.
- 🧼 Carefully wipe the top of the screen with an alcohol napkin or a special liquid for displays.
- 📱 Remove the protective glass or film if they have a darkened frame at the top.
- 🔌 Check if the cover covers the area above the speaker or next to the front camera.
- 🌡️ Make sure there is no condensation or moisture droplets on the sensor after use in the bathroom.
If the problem persists after cleaning, we'll go to software settings. MIUI The location of the settings may vary slightly, but the logic remains the same: we need to find the point responsible for the response to the approximation.
Configure through the CIT Engineering Menu
The most effective way to diagnose and initial setup is to use the built-in engineering menu. CIT (This tool allows you to test the performance of the sensor in real time and perform its initial calibration without obtaining superuser rights. USSD-debug-code.
To run the test, dial ##6484## in the dialer. If the code didn't work (which happens on some global versions), go to Settings → About Phone → MIUI version and quickly press 7-10 times on the version bar until the notification "You became a developer" appears. Then in the expanded settings menu, find "Testing" or "CIT".
In the test list, select Proximity sensor. Cover the top of the screen with your finger, which should change from 5.0 to 0.0 (or Far to Near). If you have a reaction, but the screen does not go out when you call, press the Calibration button and follow the instructions on the screen, removing and holding your hand to the sensor.
After successful calibration, be sure to restart the device so that the new parameters are stored in non-volatile memory. If the sensor shows constant activity (always 0.0) or complete silence (always 5.0) in the CIT menu, regardless of the position of the hand, this may indicate a hardware breakdown.
Activation of the sensor through hidden settings
In some MIUI builds, there is a hidden switch that force the use of the proximity sensor to be activated even if the system considers it to be faulty.This feature often helps when a software failure blocks the standard mechanism of operation, accessed through the developer menu.
First, you need to activate the developer mode, if you have not already done so: go to Settings → About Phone and quickly click 7 times on the MIUI Version. After the message about the mode activation, return to the main settings menu, select “Additional” or “Extended settings” and find the item “For developers”.
In the options list, find the section associated with input or hardware and activate the "Enable proximity sensor for incoming calls" switch (the name may vary depending on the Android version), which force the screen lock algorithm to work.
☑️ Algorithm of activation of hidden settings
It is worth remembering that after activation of the developer mode, many other technical parameters may appear in the system. Do not change the values associated with animation, refresh rate or debugging USB if you are not sure of their purpose, as this can lead to unstable operation of the interface.
Resetting settings and removing the system cache
If calibration and hidden settings didn’t help, there may have been a build-up of errors in the configuration files that run telephony, and resetting the phone and contact cache often solves the problem without affecting the user’s personal data, a secure procedure that is recommended to be done periodically.
To do the cleaning, go to Settings → Apps → All apps. Find the Phone app (tube icon) in the list, click on it and select Clean → Clear Everything or Clear Cache. Repeat the same operation for the Contacts app and System UI service.
In more complex cases, a complete reset of the phone settings helps, but this method should be resorted to only as a last resort, saving all important data before resetting. Before resetting, make sure that the battery charge is at least 60% to ensure that the process is successful.
| Action. | Impact on data | Efficiency |
|---|---|---|
| Cleaning up the app cache | Data is retained | Medium |
| Resetting CIT settings | Data is retained | Tall. |
| Full reset (Wipe) | All data is deleted | Maximum |
| Flip-flashing | All data is deleted | Maximum |
⚠️ Warning: Full Hard Reset will delete all photos, contacts and apps. Be sure to back up to the Mi Cloud cloud or your computer before starting the procedure.
Hardware problems and repairs
When all software methods are exhausted and the sensor in the CIT menu does not respond to the hand, it is a physical malfunction. In Xiaomi smartphones, the proximity sensor is often integrated into the display plume or into a separate module under the speaker. Falls, moisture or a production defect can cause it to fail.
In the models with AMOLED-With the use of screens and Under Display Camera technology, the sensor can be optical, built right into the matrix, and in such cases, it is not possible to replace the sensor separately, requiring the replacement of the entire display module, which is an expensive procedure.
There is a software solution for cases where the sensor is physically broken: using stub applications from Google Play that emulate the sensor's performance using an accelerometer (turning the phone to the ear blocks the screen), but it is a crutch that consumes the battery and works less accurately.
How does sensor emulation work?
If you are planning a self-substitution, use only original parts or quality analogues, as cheap plumes often do not have calibration data, and the screen will still behave incorrectly.
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Use Xiaomi’s Equipment Test app to quickly check all sensors before going to the service center – it will save you time and money.
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If the sensor shows constant values in the CIT menu regardless of actions, and cleaning does not help, you need to replace the hardware (the plume or display module).