Owners of the popular compact flagship Xiaomi Mi 9 SE often face a situation when during a phone conversation the screen suddenly goes out or, conversely, does not turn off when you lift to the ear. This is a direct indication of the incorrect operation of the proximity sensor. This sensor is located at the top of the display and is responsible for blocking the touchscreen during a conversation, so that you do not accidentally press the break button with your cheek or ear.
The problem can be either a software failure of the MIUI operating system or a physical contamination or damage to the hardware. Before you carry the device to the service center, it is worth conducting a thorough self-diagnosis, which will help you understand whether complex repairs or software calibration are required. It is critical not to use aggressive chemistry to clean the upper frame, as this can damage the oleophobic coating and the adhesive layer.
In this guide, we will take a look at all the sensor testing methods available, from built-in engineering tests to third-party utilities, learn how to distinguish software glitch from hardware breakdown, and learn how to properly calibrate your device for stable operation. Competent diagnostics will save you time and budget, avoiding unnecessary costs of replacing healthy components.
Symptoms of sensor malfunction
You can see that the proximity sensor is not working correctly, based on a number of characteristics that are manifested mainly during voice calls. If the screen of your Xiaomi Mi 9 SE behaves unpredictable, you should pay attention to the following points. Most often users complain that the display does not go out when you bring the phone to your ear, which leads to accidental taps and reset of the call.
The reverse is also a wake-up call: the screen turns off immediately after a conversation begins, even if the phone is at a distance, which may indicate sensor contamination or software conflict, and in some cases, there is a rattling of the screen, where it is constantly turned on and off for no apparent reason.
There are a number of key signs by which you can diagnose the problem:
- 📱 The screen does not respond to the hand being brought to the top of the case during the call.
- 👂 The interviewer complains that you hang up the phone or press buttons during a conversation.
- 🔦 Notification indicator or flash can flash strangely when the screen is locked.
- 🚫 Inability to answer incoming call with a swipe, as the touchscreen is blocked incorrectly.
⚠️ Note: If the screen only goes out in certain cases, the problem may not be the phone, but the thickness of the protective glass or the improperly cut hole for the sensor.
Ignoring these symptoms can lead to discomfort when using the device. In some cases, a faulty sensor can block the ability to use hands-free or video calls. Therefore, timely check of the sensor is an important part of smartphone maintenance.
Use of the CIT Engineering Menu
The most reliable and accurate way to test the operability of the proximity sensor on the Xiaomi Mi 9 SE is to use the built-in CIT Engineering Menu (CIT Test), which is designed for factory diagnostics and allows you to test each device module separately from the operating system, accessed through a standard settings menu.
To enter the test mode, you need to go along the path: Settings → About Phone → All settings. You should find the "Kernel Version" item and click on it 5-7 times in a row. Then the component testing menu will open. You need to find the "Proximity sensor" or "Proximity Sensor" item in the list.
Inside the test, you'll see a screen with a numerical value and instructions. Usually, the system asks you to close the top of the screen with your hand and then remove it. If the sensor is working, the value will change from 0.0 to 5.0 (or vice versa) instantly. If the reaction is delayed or the values do not change, this indicates a problem.
It's important to do the test in a quiet environment, without bright direct light falling on the top frame. Sunlight or a powerful lamp can illuminate an infrared receiver, which will cause the test to show a false positive. If the CIT test sensor works perfectly, then the hardware is good, and the problem should be looked for in the software.
☑️ Checking in CIT menu
Verification through system code
An alternative and faster way to start a diagnosis is to use a special USSD-This method allows you to bypass the long menu settings and immediately get into the interface of the hardware verification. MIUI This method works stably and does not require the installation of additional software.
Open the Phone app and type the following character combination: ##6484##. If the code is entered correctly, the CIT menu will open automatically. The verification principle here is similar to the one described above: you select the appropriate item and swipe your hands over the top of the display.
The advantage of this method is that it works even if the touch screen is not responding partially (although you still need a touchscreen to navigate the menu), and it is also useful if the settings menu is error-prone. Remember that the engineering menu does not recommend pressing buttons whose purpose you do not know, so as not to confuse the factory calibrations of other modules.
What if the code doesn't work?
Diagnostics with third-party applications
If you have built-in MIUI tools that are not available for some reason, or you want to get more detailed statistics, you can use apps from the Google Play Market. There are many tools that output raw data from sensors in real time, and this allows you to see the slightest fluctuations in readings that are not noticeable in a standard test.
One of the most popular and reliable tools is the Phone Tester or Sensor Test app, and when you install it, you run it and go to Proximity or Sensors, and you'll see a graph or a numerical value, and if you put your finger on the sensor, you'll see a jump.
Popular applications for verification:
- 📊 Phone Tester – Shows detailed information about all sensors of the device.
- 🔧 Sensor Test – a simple interface with visualization of the approximation sensor.
- 📱 AIDA64 — Professional tool for collecting information about the system and sensors.
Using third-party software is especially useful when it comes to determining whether the sensor is constantly bugging or only under certain conditions, for example, some users have noticed that after updating the system, readings in third-party applications become more stable than in a standard test.
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Before installing diagnostic applications, be sure to check permissions. Some programs may request access to contacts or calls, which is not necessary for a simple sensor test.
Hardware cleaning and inspection
Often the cause of malfunctioning is the banal pollution. At the top of the Xiaomi Mi 9 SE, next to the speaker, there is a small hole or darkened area of glass. This is where the infrared emitter and receiver are hidden. Dust, greasy fingerprints or glue residue from the protective film can block the signal.
To clean, use a soft microfiber slightly moistened with an alcohol solution (isopropyl). Gently wipe the top frame. Do not use cotton swabs, as the villi can get stuck in the speaker or sensor. It is also worth checking whether a protective film is pasted over the sensor - some thick films with black bordering over the sensor.
If you use a security glass, make sure it has a special cutout or a transparent area above the sensor. Cloudy or cheap glass can distort infrared radiation, which makes the phone "think" it's in your pocket. Take the glass off and check the sensor's operation "on a clean screen" - this will help localize the problem.
Table of possible causes of failure:
| Reason. | Symptoms. | Decision |
|---|---|---|
| Pollution | Sensor can't see the hand. | Wipe with microfiber |
| Protective glass | False positives | Replace the glass or remove |
| Mechanical impact | Total rejection. | Replacement of a plume in the service |
| Software failure | Unstable work | Calibration or discharge |
⚠️ Never try to disassemble the body of Xiaomi Mi 9 SE You can clean the sensor from the inside if you don't have experience, you can damage the plume of the display or break the tightness of the case, which will deprive you of the guarantee.
Programmatic calibration and resetting
If the sensor is physically clean but not working properly, it may have been programmed to calibrate it, and you have to force the sensor to be recalibrated, and in the CIT engineering menu, the proximity sensor check section, there is often a "Calibration" or "Calibrate" button. Press it and follow the instructions on the screen (usually you have to close the sensor and open it several times).
Some versions of MIUI have a hidden calibration function available via the engineering menu: Enter ##64663## (if available on your version) or use the Engineering Mode app from the Play Market. Find the "Proximity Sensor Calibration" item there and start the process. Once the calibration is successful, the phone may need to restart.
A radical but effective method is to reset the settings to factory settings. This will delete all user data, so be sure to back up. Go to Settings → Advanced Settings → Restore and Reset → Reset. Often, after a clean system installation, the sensor problem disappears as conflicting caches and settings are removed.
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Calibration through an engineering menu is the most effective software method of solving a problem if physical cleaning has not helped.