Redmi 9 series smartphones are deservedly considered one of the most popular budget devices, but their users often face the unpleasant problem: the screen goes out during a conversation, and the interlocutor is not heard. In other cases, the screen does not turn off when you hold the phone to your ear, which leads to accidental cheek pressing, all these symptoms indicate an incorrect approach sensor that requires immediate calibration.
Fortunately, the MIUI shell on which the Android system is based in these smartphones has powerful tools for diagnosing and tuning the hardware. You don't have to be a skilled programmer to fix this error. You just have to follow the instructions precisely and use the hidden engineering menu available to every device owner.
In this article, we will take a look at all the available methods for restoring the sensor to its proper functioning, look at both standard software methods for resetting settings and deeper methods through the engineering menu, and also touch on the physical causes of malfunctions that are often ignored by users.
Reasons for the incorrect operation of the sensor
Before you start to manipulate codes and menus in a complex way, you need to understand the nature of the error, and most often the problem lies in a software failure when the device driver stops reading the infrared emitter correctly, which can occur after you update the system, install a heavy third-party launcher, or simply because of the accumulation of system debris.
But physical factors are also not to be discounted: the proximity sensor in Xiaomi Redmi 9 is located at the top of the screen, often under the protective glass. If dust, greasy traces accumulate on the surface of the glass, or if a poor-quality protective glass with a black frame overriding the sensor is pasted, software calibration may not help.
It’s also worth noting that some third-party applications, especially those that manage calls or lock screens, can conflict with standard MIUI services. In rare cases, the cause is degradation of the component itself, but this is extremely rare on modern devices.
⚠️ Note: If your phone has recently been in water or been hit hard, the problem may be that the sensor plume is physically detached, in which case the software calibration will be useless and you will need to disassemble the device.
Understanding the cause will help you choose the right recovery strategy, and if you're sure that the screen is clean and the protective film is flat, then it's likely that the wrong calibration parameters are the ones we're going to be fixing.
Preparation of the device for diagnosis
To successfully perform the calibration procedure, certain conditions must be created. First, make sure that your Redmi 9 battery is at least 30-40%. Although the calibration process consumes little power, suddenly turning off the smartphone while writing reference values can lead to additional software errors.
Second, clean the top of the screen, use microfiber to remove fingerprints and dust in the area of the speaker, and that's where, under the grid or directly in the glass, there's an infrared sensor, and even a thin layer of skin fat can distort the readings, and you'll calibrate the device incorrectly.
Third, close all running applications. Calibration requires access to system resources, and background processes can interfere with measurement accuracy. SIM-card and memory card to exclude any communication interruptions during the test.
Method One: Standard calibration through an engineering menu
The most efficient and safest way to fix the sensor is to use the built-in CIT (Customer Integration Test) menu, a tool designed by Xiaomi engineers for exactly that purpose. You don't need a superuser's license to log in to the menu, access is open by default.
Open the Phone app and dial the combination ##6484##. If the code is entered correctly, the testing menu will automatically open. If nothing happens, check if the input function is disabled. USSD-codes in your operator’s settings or a third-party application.
In the list that opens, look for the Proximity Sensor, which is usually at the top of the list, or it has a number that matches the order of the tests. Click on it, and you'll see a screen with two values: Distance and status: Near or Far.
The essence of calibration is to show the system reference values. Close the top of the screen with your palm (simulating the ear touching), the value should change to "Near", and the digital value of the distance should become minimal (usually 0.0 or 1.0). Remove the palm, it should appear "Far" and a value of about 5.0.
What if the code doesn't work?
If the standard code ##6484## does not open the menu, try the alternative code ##4636» -> menu) -> Test. To start the calibration process, press Calibration or Pass (depending on the firmware version). Follow the instructions on the screen: you will be asked to close the sensor and open it several times. After successfully completing the test, press Pass to save the results, or Fail if the test is not passed. Method two: hidden settings through the Phone app In some versions of the shell MIUI Redmi 9 has an alternative calibration path that doesn't require you to go to the full engineering menu, which is less well known, but often more effective if the first method fails. To do this, open the Phone app, click on the three dots in the top right corner, and select Settings. In the menu that opens, look for the Incoming Calls section. Inside this section, you may have a "Draw-up Sensor" option. If you have one, click on it. You'll see a switch or calibration button. Press "Calibrate" and follow the instructions: Close the top of the screen with your hand, then remove your hand. If there's no such item, it means that your version of the firmware will sometimes hide the difference between the apps, try to return the menu. The engineering menu tests hardware directly, bypassing many software filters, while the settings in the call menu work at the call software level. Using both methods in combination gives the best result. Comparing calibration methods Users are often lost, which way to choose for their device. To simplify the choice, we have prepared a comparison table that will help determine the optimal solution to the problem depending on your situation. Characteristics Engineering menu (CIT) Call settings Third-party applications Access Hidden Code Menu settings Google Play Depment Depment Hardware layer Software layer Software, the most effective tool is the high level of the 50% security (the most effective tool) It works at a low level and allows you to reconfigure the sensitivity of the sensor regardless of the installed system updates. This is the method recommended to use first. Call settings are good for quick verification, but they often depend on the version of the "caller." Third-party applications from the Play Market store, such as "Proximity Sensor Reset & Test", should only be used as a last resort, since they require unnecessary resolutions and may not work correctly with a particular "hardware" Redmi 9. If the software methods did not help, and the sensor continues to behave inadequately, the problem is almost certain to be in the physical zone of the Redmi. The makers of these glasses often make the cutout for the speaker and the camera inaccurate. If the black glass frame even slightly overlaps the area of the sensor, it will think that the phone is constantly in the ear, and turn off the screen. Take off the safety glass or film and run the test in the engineering menu again. If the sensor works perfectly without the glass (shows "Far" in normal condition and "Near" only when completely closed with your finger), then it is the glass that is to blame. ⚠️ Warning: Do not try to seal the sensor with tape or tape for "calibration"; this will cause the screen to burn constantly during the conversation and discharge the battery, and can damage the sensitive element when peeled off, and it is also worth checking whether moisture has entered the speaker grid. Water can create an optical lens or completely block IR radiation. In such cases, it helps to clean clean clean with a soft brush or use silica gel bags in a sealed container with the phone (off) for the day. Resetting and radical measures When neither calibration nor cleaning helps, there is the last software frontier - a complete reset. This action will return all system parameters, including drivers and sensor configuration files, to factory state.Be sure to back up all important data before performing this procedure, as all contacts, photos and applications will be deleted in the process. → The phone. → Resetting settings → Delete all data. Don't install all applications immediately after you reboot. First, check the sensor on the clean system. If the problem disappears, then some third-party application caused the conflict. If the problem is still on a clean system, the probability of hardware failure tends to 100%, in rare cases, helps to flash the device through the computer using the utility Mi Flash Tool. This will reinstall all system partitions, including those that run the communication modules and sensors. However, it is a complex process that requires unlocking the bootloader, which can void the warranty. Frequently asked questions (FAQ) Why does the proximity sensor work intermittently? Unstable operation often indicates a sensor contamination or a crack in the protective glass that refracts light. It could also be a sign of overheating of the processor, which temporarily affects the performance of the peripheral modules. MIUI New versions of firmware can contain driver errors or change sensitivity thresholds. If the problem appears immediately after the upgrade, waiting for a patch or rollback on the previous version of the system may be the only solution. Does the magnetic case affect the sensor? Magnetic bookcases usually affect the magnetic sensor (compass), but not the infrared proximity sensor. However, if the case has a too thick cover or a poor-quality cutout, it can physically lock the sensor. Should the sensor be calibrated after changing the screen? Necessary. When replacing the display, the sensor itself changes (it is often embedded in the screen plume) or the protective glass. Without the screen, the new screen can not determine the distance of the new object.