Xiaomi Redmi 9T has proven to be a reliable device with excellent autonomy, but users often face the nuances of the sensors. One of the common problems is the incorrect operation of the proximity sensor, which during a conversation, the screen does not go out when you bring the phone to the ear. This can lead to accidental cheek pressing and resetting the call, which significantly reduces the comfort of using the gadget. In this article, we will discuss in detail the mechanisms of this component and how to fine-tune it.
The problem can be both software failure and physical locking of the sensor with a protective film. Unlike some flagship models that use ultrasonic technology, the Redmi 9T uses a classic infrared sensor that requires line of sight. Understanding how it works will help you diagnose the cause of the malfunction faster and choose the right solution method.
Before you start complex manipulations, you should make sure that there is no contamination on the surface of the screen. Fat spots or thick protective glass can distort the sensor readings. If external factors are excluded, then software calibration of the sensor is likely necessary. Below we will give step-by-step instructions to help return the device to work properly.
The operating principle and location of the sensor in the Redmi 9T
In the Redmi 9T, the proximity sensor is located at the top of the front panel, directly above the display. It works by emitting infrared light and analyzing its reflection from objects. When you bring the phone to your head, the infrared beam reflects off the surface and hits the receiver, after which the system receives a signal to lock the screen. It is important to understand that this process is instantaneous, and any delay often indicates software lag or contamination.
Sometimes users confuse the proximity sensor with the light sensor, although in modern smartphones they are often combined into one module. The light sensor is responsible for automatically adjusting the brightness of the screen, while the proximity sensor controls only the state of locking the display during calls. On the Xiaomi Redmi 9T, this module is hidden under a black frame, so it is difficult to see visually. It is the lack of a visible hole that makes the device more protected from dust, but complicates diagnosis.
⚠️ Attention: Incorrect calibration may cause the screen to go out in your pocket or, conversely, not to respond to the ear.
It's also worth noting that the sensor is closely related to the system settings of the MIUI shell. Sometimes operating system updates can reset user settings or make changes to data processing algorithms. If you notice strange behaviors in the screen after updating the firmware, first check the relevance of the sensor settings. This will help to eliminate software conflicts.
Diagnosing faults through the CIT hidden menu
To accurately test the performance of the hardware in Xiaomi smartphones, there is a special engineering menu known as the CIT (Customer Information Test), accessed through the standard Phone application, enter a special code that allows you to start testing all the components of the device, including sensors, vibrator and screen, this is the first step that you need to take before any calibration.
To get into the diagnostics menu, open the caller and dial the combination ##6484##. Once you enter the last digit, the device will automatically go into testing mode. In the list that opens, you need to find the item responsible for checking the sensors, usually called "Proximity Sensor" or "Proximity Sensor." When you click on it, you will see the current sensor readings in numerical form.
☑️ Testing the sensor in CIT
In the test, the screen will change color or show the status of "Pass" / "Fail"; you need to close the top of the screen with your palm, simulating the application to the ear. If the numbers change (usually from 5.0 to 0.0 or vice versa), then the sensor is physically healthy and responds to obstacles. If the values remain unchanged even when the sensor area is completely closed, there may be a hardware breakdown or a critical driver failure.
The CIT menu also allows you to recalibrate directly in the test mode. This often uses a "Calibration" button or similar. The system will ask you to remove your hand from the screen and then close it. Once you pass the test, the data will be recorded in memory. However, if standard calibration through the CIT does not help, a deeper intervention through the engineering menu may be required.
Calibration through the Engineering Menu and ADB
If standard methods fail, you can try more advanced tools. Android's engineering menu provides access to hidden configuration options. It often uses the same code ##6484## to enter, but with the transition to the single-player test section. Here you can find the option to reset the sensor calibration. Pressing the Calibrate button triggers the reconfiguration process of sensitivity.
For more experienced users familiar with USB debugging, the method is available via ADB (Android Debug Bridge), which allows you to send commands directly to the system. Before starting work, you need to turn on the USB debugging mode in the Developer menu. By connecting the phone to a computer, you can execute a command to reset the sensor settings, which is especially useful if a software failure blocks standard interfaces.
adb shell settings put system proximity_sensor_calibrated falseOnce this command is executed, the device must be restarted in the terminal, the system will detect a lack of calibration data on the next run and will attempt to perform the initial setup automatically. This method often helps in cases where the sensor is stuck in one position due to a software conflict, but be careful, since interference with system settings requires accuracy.
Risks of using ADB
Program settings and resetting parameters
Often, the problem is solved without using complex codes, but by simple actions in the interface. First of all, check if the Approximation Sensor function is enabled in call settings. The path to this option may differ from one version of MIUI, but it is usually in the Call Settings or Advanced section. Make sure the switch is active.
If the setting is enabled but not working, try clearing the cache of the Phone app and system services. Accumulated temporary files can cause conflicts. Go to Settings → Apps → All apps, find Phone and select Clear Cache. It’s also worth checking for system updates, as new security patches often fix sensor errors.
- 📱 Restart the device to Safe Mode to eliminate the impact of third-party applications.
- 🛡️ Check if antivirus or memory cleaning app is blocking sensor access.
- 🔄 Reset all settings to factory (without deleting personal data) if the problem has occurred after installing the theme.
In some cases, a third-party user-installed call may cause conflict, so try temporarily removing applications like Truecaller or other analogues and checking the standard interface, and if the sensor worked correctly after removing third-party software, then the reason was precisely because the software was incompatible.
Influence of protective glasses and accessories
One of the most common reasons for the sensor to malfunction on the Xiaomi Redmi 9T is the wrong security glass. Many users buy cheap accessories that have a black perimeter bezel, which can block the IR sensor, which makes the phone “think” that it is constantly in the ear, and extinguishes the screen.
To test this factor, take a close look at the top of the screen when the display is off. If you see the security glass coming into the area above the speaker where the sensor is located, the problem is probably this. The solution is one: replacing the accessory with a model with a cutout under the sensor or a quality glass with a transparent top.
⚠️ Attention: Even a microscopic crack in the sensor area can scatter the infrared beam, causing false positives.
Some massive high-sided protective cases can partially cover the sensitivity zone, especially if the phone is on the table. In such cases, the screen may not light up on an incoming call until you take the device in your hand. Remove the case for verification - if the problem is gone, then the accessory is unsuccessfully selected.
Comparison of methods of problem-solving
For the convenience of users, we have created a table that will help you choose the best method of solving the problem depending on the symptoms. Different situations require different approaches, from simple cleaning of the screen to flashing the device. Using the right method will save you time and nerves.
| Symptoms. | Probable cause | Recommended method | Difficulty |
|---|---|---|---|
| The screen doesn't go out in the ear. | Dirt or film | Cleaning/Replacement of glass | Low. |
| The screen goes out in your pocket | Calibration failure | Calibration via CIT | Medium |
| Sensor's not responding. | Hardware failure | Service centre | Tall. |
| Problem after update | Bug MIUI | Resetting settings/Resetting | Medium |
As you can see from the table, most problems are solved by software or by replacing accessories. However, if none of the methods worked, and the CIT sensor shows zero values or an error in the CIT menu, this may indicate a physical breakdown of the plume or the module itself. In this case, self-repair is not recommended, you should contact an authorized service.
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In 80% of cases, the problem is solved by replacing the protective glass with high-quality or simple cleaning of the top of the screen from fat.
Additional Optimization Tips
To prevent future sensor problems, it is recommended to regularly check the condition of the top of the smartphone. rub the screen with a soft cloth, especially after talking, as skin fat can create a dense film that interferes with the passage of IR rays. It is also not recommended to use aggressive chemicals for cleaning, which can damage the oleophobic coating.
If you use your smartphone frequently in dusty conditions, try to put it down less often on soft surfaces such as sofas or clothes. Fabric microvilli can clog the speaker grid and the sensor area, gradually reducing its sensitivity. Regularly blowing the speakers with compressed air (carefully!) will help keep the device clean.
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Use the Pocket Mode feature in lock settings if it is available in your version of MIUI.It adds extra protection against random taps, requiring double tap to unlock.
Remember that Xiaomi's software is constantly evolving. Keep an eye out for updates to the About Phone menu, as the company's engineers often release patches that improve sensor performance. Ignoring updates can leave your smartphone vulnerable to known bugs that have already been patched by developers.