The situation when the screen of a Xiaomi smartphone suddenly goes out during a conversation, and the interlocutor hears only silence, is familiar to many owners of devices of this brand. Often the cause of this behavior is not a software failure, but a banal contamination or a physical defect of the proximity sensor located at the top of the case. This miniature device continuously scans the space in front of the screen to turn off the display when you bring the phone to the ear, preventing accidental brushing.
In modern Redmi and Poco models, the sensor is often hidden under the display glass, making it vulnerable to the accumulation of dust, grease and condensation.If you notice that the screen has stopped responding to the removal of the phone from your face or, conversely, does not go out when talking, you need to conduct a diagnosis. Ignoring the problem can lead to you missing important information or accidentally start unnecessary functions during the call.
Before you take the device to the service center, you should try to solve the problem yourself using proven cleaning methods and software calibration. In this article, we will discuss in detail the physical ways of eliminating contaminants, working with the engineering menu and the specific settings of the MIUI system, which often affect the correct operation of the sensor.
The principle of operation and types of sensors in Xiaomi smartphones
Understanding how the sensor works helps diagnose the problem more effectively. Most budget and mid-budget Xiaomi models, such as the Redmi Note series, use an infrared sensor. It emits an invisible beam and reads its reflection from objects. If the beam reflects too quickly, the system thinks that the phone is near the ear, and turns off the screen. In more expensive flagships, the capacitive principle can be applied, but IR sensors remain the standard because of their cheapness and reliability.
The challenge is that the pollution can be microscopic: a film of fat from a finger or a thin layer of dust in a speaker hole can completely block the IR beam. The optical sensor system is extremely sensitive to transparent but greasy contamination that the human eye may not even notice, which is why simply wiping the screen often fails unless you clean the sensor area directly.
And design is also important. Some models have a speaker-to-speak sensor or a narrow slot above the screen, and it's the perfect storage device for pocket villi and earwax. If you're wearing a phone without a cover or in a fabric case, the likelihood of clogging that area increases many times, and in these cases, more thorough mechanical cleaning is required.
Physical cleaning of the sensor and elimination of contaminants
The first and safest step is to thoroughly physically clean the top of the device, and you'll need a soft, hairless microfiber wipe lightly soaked in isopropyl alcohol or a special screen cleaner. It's important not to use aggressive chemistry that can damage the oleophobic coating or the glue that holds the protective glass.
If visual inspection shows the presence of dust inside the mesh speaker or sensor hole, you will need to use compressed air. compressed air canisters allow you to blow out fine dust that is stuck deep in the channels. It is strictly forbidden to use vacuum cleaners or mouth breathing for this purpose, because static electricity vacuum cleaner or moisture from the mouth can cause electronics irreparable damage. Air jet must be directed at an angle, so as not to press dirt deeper.
For persistent contaminants that are not removed by air, you can use a soft antistatic brush. With easy sweeping movements, try removing the villi from hard-to-reach areas. If you use a protective glass, make sure that it is glued flat and does not overlap the sensor's work area. Often users do not even realize that the problem is precisely the displacement of the protective glass, which creates an optical barrier to IR rays.
☑️ Checklist of physical cleaning
⚠️ Warning: Never use sharp objects such as needles or toothpicks to pick through the sensor holes.You can damage the safety net or worse, breach the sensor element itself, which will result in the need to replace the entire plume.
Diagnostics through CIT Engineering Menu
If physical cleaning didn't work, check if the sensor itself sees objects. The MIUI shell has a built-in engineering menu that allows you to test all components of the phone. To log in, open the Phone app and enter the universal code ##6484##. Once the last characters are entered, the device will automatically go to the CIT (Customer Information Test) menu.
In the list that opens, you'll find a point associated with the proximity sensor, which can be called Proximity Sensor, PSensor or just "Parking Sensor." Select this item. You'll see a window with two digital values: Distance and Status. In a calm state, when there's nothing in front of the top of the phone, the distance should be 5.0 cm (or close to 5.0), and the status is Far.
Hold your hand or finger to the top of the screen at a distance of 2-3 cm. Values should change: distance will decrease to 0.0 or 1.0, and status will change to Near. If the values do not change at all or change randomly even without obstacles, this indicates hardware malfunction or critical contamination. If the test is successful, but in normal calls the screen goes out, the problem can be software.
What if the code doesn't work?
Calibration of the proximity sensor
Often, the sensor is physically clean and clean, but it's got a bad reading, and you have to have a forced calibration. Go back to the CIT menu, select the Proximity Sensor, and find the Calibration button. Press it and follow the instructions on the screen. Usually, the system will ask you to remove your hand from the phone and then close the sensor. Once the procedure is complete, the data will be overwritten.
There is also a hidden method of calibration through system settings, which works on many Xiaomi and Redmi models. Open the Phone app, go to call settings and look for the Approximation Sensor. If there is a calibration option, run it. However, the more reliable way is to use engineering code to reset the sensor settings. Enter the code ##7726## (if supported by your version of MIUI) to reset the calibration.
After calibration, be sure to restart the device. Reboot is necessary for the Android operating system to re-interview hardware drivers with updated parameters. If after calibration and reboot the problem persists, consider resetting the settings to factory, but only after you have created a backup of the data.
Program conflicts and system settings
Sometimes the proximity sensor on Xiaomi is blocked by third-party apps or system functions, check if you have smart call blockers, number detectors or call recording apps, which request access to the sensor and may not process its signals correctly, causing false positives.
You should also look at Pocket Mode, which is designed to lock your phone in your pocket, but often works too aggressively. To check its effect, go to Settings → Lock screen (or Lock and Protect), and find Pocket Mode, try to turn it off and check your phone's call performance, and in some cases, this completely solves the problem of spontaneous screen quenching.
Design themes can be another source of problems. Third-party themes downloaded from Themes store may contain errors in screen control scripts. If the problem occurs after a change of theme, return the standard design. Xiaomi system themes are optimized and less likely to cause conflicts with sensor drivers.
| Symptoms. | Probable cause | Method of decision |
|---|---|---|
| The screen doesn't go out when you ring. | Fat sensor contamination | Cleaning with a spirit napkin |
| The screen goes off immediately when dialing | Failure of calibration or protective glass | Calibration in CIT or glass replacement |
| Interlocutor hears himself (echo) | Upper microphone contamination | Cleaning the speaker grid |
| Accidental cheekstrokes | IR beam malfunction | Replacement of a plume or module |
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If neither physical cleaning, nor calibration, nor resetting of settings help, most likely, the sensor module itself failed or the plume was damaged, which requires replacing the part in the service.
Specific problems of Redmi and Poco models
Owners of Redmi and Poco smartphones often face a unique problem with the location of the sensor. In a number of models (for example, Redmi Note 8, 9, 10), the sensor is located extremely close to the speaker grid or even combined with it, which leads to the fact that even a minimal amount of earwax or dust clogs the channel, and the phone “thinks” that it is constantly near the ear.
For these models, there is an additional software crutch that can be activated through an engineering menu. In the proximity sensor test, the option of switching between modes of operation (for example, from IR to capacitive, if hardware allows), however, most often only a thorough brushing of the toothbrush (dry and soft) area of the speaker helps, since dirt accumulates in the ribs of the mesh.
Also worth mentioning is the problem of sticking after a firmware update: After major MIUI updates (like switching from MIUI 12 to 13 or 14), users complain about sensors in large numbers, due to changes in energy saving algorithms, in which case cleaning the system cache through Recovery Mode or waiting for a patch from developers helps.
⚠️ Warning: If you notice that the sensor stopped working after the phone fell or moisture hit, no software calibration will help. 90% of the time, it's a physical displacement of the plume connector inside the housing, and it requires disassembling the device.
When hardware replacement is needed
If all software methods are exhausted and physical cleaning has failed, the last option is a hardware malfunction. The proximity sensor in Xiaomi smartphones is often made as a separate small module on a flexible plume or soldered into a board. Its life is not infinite, and over time it can simply burn out or lose sensitivity.
Replacing this component is not the most difficult procedure for an experienced craftsman, but requires accuracy. In most cases, it is not the tiny sensor itself that changes, but the entire plume on which it is mounted along with the buttons or the bottom microphone (depending on the design of the model), the cost of such a part for popular Xiaomi models is usually low, making repairs economically feasible.
Remember that self-replacement without experience can damage other components, especially if you need to remove the display. If your phone is on warranty, any trace of the autopsy will lead to its loss.