Xiaomi Redmi 9C is a popular budget device that, like many devices in this segment, is equipped with a contactless proximity sensor. This component is located at the top of the display and is responsible for automatically turning off the screen during a conversation when the phone is brought to the ear. Correct operation of this module is critical for comfortable operation, as malfunctions in its operation lead to accidental cheek presses and connection interruption.
Owners often experience a screen that goes out too early or doesn't respond to an object approaching, and in such cases, software interventions are required to adjust the sensor sensitivity, and sensor calibration is a standard procedure for resetting the sensor's factory settings and setting new correct responses to the obstacle.
Ignoring the problem can lead to the fact that during an important conversation you will not be able to hang up the phone or turn on speakerphone. In this article, we will discuss in detail all the available ways to diagnose and configure this component on the shell of MIUI. You will learn how to use hidden engineering menus and third-party utilities to restore the system.
Diagnosis and detection of malfunctions
Before you start taking active reconfiguration actions, you need to make sure that the problem is a software failure, not physical damage or contamination. The first step should always be visual inspection of the top of the screen. If there is a buildup of dust, fat or glue from the protective film on the protective glass or in the area of the speaker, the sensor will not work properly.
To test the performance of Xiaomi Redmi 9C, there is a built-in diagnostic tool that allows you to monitor the sensor readings in real time without having to make calls, it is the most secure method of initial verification, which does not require the installation of additional software.
☑️ Primary diagnosis
To run the test, open the Phone app and enter a special code. The screen will show a menu where you can select the testing of various modules. We are interested in the item related to the Proximity Sensor. When you hold your palm to the top of the case, the value should change from 5.0 to 0.0 (or vice versa, depending on the firmware version). If there is no reaction, the problem may be hardware.
⚠️ Attention: If after cleaning the screen and restarting the sensor does not respond in the engineering menu, it is possible that the sensor plume has departed or the component has failed.
Use of the CIT Engineering Menu
The most reliable way to calibrate the sensor on the Redmi 9C is to use the hidden CIT (Customer Integration Test) interface, which is designed for factory engineers, but is also available to ordinary users, which allows you to reset current values and write new reference values.
To enter the test mode, go to the dial menu and enter the combination ##6484##. Immediately after entering the last digit, a list of all available tests will open. Find the Proximity Sensor item in the list and click on it. A window will open before you with the current readings and control buttons.
The calibration process is two-step, and you first remove all the items from the top of the phone and press the De-Calibrate button, and then you'll see a message on the screen that you've successfully reset, and then you'll have to close the top of the screen with your palm or a thick cloth and press Calibrate.
- 📱 Make sure nothing closes the sensor before starting the reset.
- 🖐️ Close the top of the screen with your palm when recording new data.
- ✅ Wait for the “Calibrate Success” message before leaving the menu.
Once the procedure is completed successfully, the device may automatically restart or suggest manually restarting, as the new sensitivity settings are only applied after the full system cycle is complete.
What if the code doesn't work?
Configure through the system menu
Some versions of the MIUI-based Android operating system make it easier for the Redmi 9C to set up via the standard settings menu, a method less accurate than the engineering menu, but can help in cases where a failure is caused by a software conflict rather than a downed calibration.
To find these settings, go to Settings, then select About Phone and quickly click on Kernel Version or MIUI Version several times until you have become a developer, and then a new Developers option will appear in the main settings menu.
Inside the developer menu, you should look for sensor-related options. However, most often direct calibration is not available here. Instead, you can try resetting the system's applications. Go to Settings → Apps → All apps, find the Phone app and Google Play Services, then select Clear → All data.
| Parameter | Default value | Recommended action |
|---|---|---|
| Sensitivity | Medium | Calibration via CIT |
| Screen delay | 15 seconds | Change |
| Pocket mode. | Included. | Turn it off for the test. |
It is important to note that application data reset does not delete your contacts or call history, but resets the settings of the call app itself.This can eliminate software errors that interfere with the correct processing of signals from the proximity sensor.
Application of third-party applications
If the built-in Xiaomi tools do not give the desired result, you can use specialized software from the Google Play store. There are many utilities that can force the calibration process or change the system configuration files without root rights.
One of the most popular and proven applications is Proximity Sensor Reset & Test, which automatically determines the model of your smartphone and offers the optimal calibration scenario. Once installed, the application will request permission to use special features that must be provided for proper operation.
The customization process in a third-party application is usually this: you put your phone on a flat surface, press the Start button and wait for the process to end. The program flashes the screen several times and vibrates to signal completion. After that, reboot is also mandatory.
- 📥 Download applications only from official sources.
- 🔒 Read the requested permissions carefully before installation.
- 🔄 Always back up your data before using system utilities.
⚠️ Warning: Third-party apps may have access to your data. Use only proven utilities with high ratings and a lot of positive reviews.
Impact of protective accessories
A common cause of sensor malfunction on the Redmi 9C is the wrong security accessories. Budget models often have a sensor located very close to the edge of the display or in the frame, making it sensitive to any overlap.
Black-framed protective glass or poor quality films can partially block the range of the infrared emitter, and even a microscopic layer of glue or an air bubble in that area can distort the signal, making the phone think it's in your pocket.
If you notice that the problem occurred after sticking a new protective glass, try to remove it carefully and check the sensor. In some cases, cutting a small hole in the protective film above the sensor helps, although this spoils the appearance.
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When buying a Redmi 9C security glass, choose options marked “Case Friendly” or a transparent frame so as not to overlap the sensors and camera.
Also worth noting are the cases. Some models of book covers or bumpers with high sides can press on the screen or overlap the top of the case. Shifting the case even by a millimeter can lead to permanent darkening of the screen during a conversation.
Resetting and extreme measures
When none of the above methods worked, the radical but effective way is to completely reset the device to factory settings, which will remove all user data, apps and settings, returning the phone to the “out of the box” state.
Before performing this procedure, be sure to back up all important data. Photos, contacts and documents can be saved to the Mi Cloud cloud service or to your computer. Reset is done through the Settings menu → About phone → Resetting → Clear all data.
After you reset and set up your phone, don't install all the apps at once. First, check the proximity sensor on the clean system, and if it works correctly, it means that some installed application or system conflict caused the problem.
- 💾 Make a full backup of the data before resetting.
- 🔋 Charge your phone to at least 60% before starting the process.
- ⏳ Do not interrupt the resetting process, it can lead to breakdown.
If, even after a complete reset and installation of only system updates, the sensor behaves inadequately, the probability of hardware failure tends to 99%, in which case the plume or the sensor module itself in the service center must be replaced.
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A complete reset is the last software method to solve the problem, and if it doesn't work, you need to repair the hardware part.