Redmi smartphones have long proven to be affordable devices with wide functionality, but the software features of the MIUI shell sometimes raise questions among users. One of the common problems faced by owners of the Redmi 9C NFC model is the incorrect operation or complete lack of response of the proximity sensor, which is expressed in the fact that during a conversation the screen does not go out when the phone is held to the ear, which leads to accidental cheek pressing and interruption of the call.
In this article, we will discuss in detail how to activate this sensor, calibrate it, and fix software failures that can block its operation. It is important to understand that in most cases, the problem is not a physical failure, but a software failure or the need to manually adjust through an engineering menu. The proximity sensor is an infrared sensor located at the top of the display, and its proper operation is critical for comfortable communication.
Before we get into the complicated manipulations, it’s worth noting that the Xiaomi Redmi 9C NFC model features a classic design with a cutout in the screen, where the module is hidden. If you notice that the phone has stopped responding to your actions during the call, don’t rush to carry the device to the service center. Often, it is enough to follow a few simple reset or calibration steps to return functionality to the system.
Checking the physical condition and cleaning the sensor
The first and most obvious step that users often ignore is to check the cleanliness of the top of the screen. On the Redmi 9C NFC model, the sensor is located in a narrow strip above the display. Dirt, greasy finger marks or dust can completely block access to infrared radiation, which makes the system believe that an object is nearby, or vice versa, not see it.
Carefully wipe the top of the device with a soft microfiber, slightly moistened in a special solution for screens. Do not use aggressive chemistry or abrasive materials, as they can damage the oleophobic coating or the plastic case itself. Pay special attention to the areas around the front camera and the speaker.
⚠️ Warning: Using low-quality protective glass or film with incorrect cutouts may physically override the sensor. If the problem occurs after the protection sticker, try temporarily removing it to check.
It's also worth checking if the phone has a thick protective film that shifts the focus of the sensor, and in some cases, even a microscopic crack at the top of the screen can disrupt the infrared module, and if the situation hasn't changed after careful cleaning, we'll go to software diagnostics.
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Use the phone's flashlight, pointing it at an angle to the top of the screen to see the light glow of the proximity sensor. If there is no glow even in the engineering menu, there may be a hardware malfunction.
Diagnostics through CIT Engineering Menu
For deep testing of hardware components in Xiaomi smartphones, there is a built-in CIT tool (Customer Integration Test), which is a hidden menu that allows you to test each module separately, including a vibrator, camera, microphones and, of course, a proximity sensor, accessed through the standard Phone application.
To get into the diagnostic menu, open the dial and type ##6484##. Immediately after entering the last digit, the list of tests will open. Find a item in the list called "Proximity sensor" or "Proximity Sensor." When you click on it, you will see the current readings of the sensor.
In the window that opens, you'll see a numerical value. If you close the sensor with your finger, the value should change (usually from 5.0 to 0.0 or vice versa, depending on the software version), If the numbers change, then the sensor is physically healthy, and the problem lies in the system settings or application conflict.
☑️ Checking in CIT menu
If the values remain unchanged even when you close the top of the screen, this may indicate a more serious driver failure or hardware problem, in which case you perform the calibration, which will be discussed in the next section.
Calibration of the proximity sensor
Calibration is a sensor sensitivity adjustment process that helps the system correctly determine the distance to the object. On the Xiaomi Redmi 9C NFC, this procedure can be done in two ways: through the same engineering menu or using a special code. Often, it is downed calibration data that is the reason why the screen does not go out during a conversation.
To start automatic calibration in the CIT menu (where we've been) select the sensor test and press the Calibration button. Follow the instructions on the screen: normally, the system will ask you to remove your hand from the phone and then close the sensor.
An alternative method is to use a special code to reset the calibration. In the Phone app, type ##64663##. This code can vary depending on the version of MIUI, so if the former did not work, try to find the "Proximity sensor calibration" item in the settings menu by typing the word "calibration" in your settings search.
| Method | Action. | The result |
|---|---|---|
| Engineering menu | Code ##6484## | Manual test and reset |
| Special calibration code | Code ##64663## | Automatic setup |
| Mi Remote appendix | Search in settings | Finding Hidden Options |
| Resetting settings | Complete data reset | Return to factory parameters |
After successful calibration, be sure to restart the device, and reboot is necessary in order for the new sensitivity parameters to apply to the entire system and the operating shell begins to use the updated data.
What if calibration doesn’t help?
System settings and applications "Phone"
Sometimes the sensor works perfectly, but the settings of the call app block its correct operation. Xiaomi smartphones by default use the app “Phone” from Google or the own development of MIUI Dialer. Depending on the version, the path to settings may differ, but the logic remains the same.
Open the Phone app, click three dots in the corner (or the gear icon) and select Settings. Find the Incoming Calls or Pocket Mode section. Make sure that the Pocket Mode feature is on, as it activates the lock screen when approaching. If this switch is off, the screen will burn constantly.
It's also worth checking if there are any third-party themes installed. Some custom themes may conflict with the system's screen control processes. Try switching to the standard MIUI theme and checking the sensor again.
- 📱 Open the settings of the "Phone" application».
- 🔍 Find the item "Mode in your pocket».
- ✅ Make sure the switch is active.
- 🎨 Check if the current theme is affected.
If you use third-party calling apps (like Truecaller or Skype), their settings can override system settings, so you need to look for the appropriate options inside the caller app itself.
Impact of Updates and Third-Party Apps
One of the hidden causes of malfunction can be recently installed applications or system updates. After updating MIUI on Redmi 9C NFC, access rights are sometimes reset or software bugs occur that block the operation of touch modules.
Analyze which apps you've recently installed, especially memory cleaners, antiviruses, or call management applications, which may take precedence over system settings and block the sensor, try to remove suspicious programs and check the results.
⚠️ Warning: Do not install apps from unverified sources that promise to “accelerate the sensor” or “fix the screen.” Often they contain malicious code that disrupts the entire Android system.
It’s also worth checking for updates for the system itself. Go to Settings → About Phone → MIUI version and click “Check Updates.” Developers often release patches that fix known sensor bugs.
If the problem started immediately after the firmware update, there may be an error in the new version, in which case users often wait for the next update or perform a full reset (Wipe Data), saving important information beforehand.
Hardware malfunctions and repairs
If none of the software methods worked, and in the engineering menu, the sensor shows the same values regardless of the position of the hand, the probability of hardware failure is high. In the Redmi 9C NFC model, the proximity sensor can be soldered on the display plume or on a separate board connected to the motherboard.
A common cause of failure is moisture, and even if the phone is not sinking, high humidity or condensation can oxidize the sensor contacts, requiring disassembly of the device, ultrasound cleaning of the contacts, or a module replacement.
Self-repair without experience is not recommended, as you can damage the plumes or screen, it is better to contact an authorized service center, where you will diagnose and replace the part if necessary, replacing the proximity sensor usually does not take much time and is not expensive procedure.
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If the sensor values do not change in the engineering menu when closed with a finger, software methods are powerless - hardware repair or replacement of the plume is required.