The situation of the phone’s screen turning off while talking on the Xiaomi Redmi 9T is one of the most common complaints of users, although this is not initially a malfunction. Standard behavior of the Android operating system and the MIUI shell involves turning off the display when holding the smartphone to the ear to prevent the accidental pressing of the reset buttons or hands-free communication. However, the problem occurs when the screen goes out too early, does not light up at all, or the phone stops responding to commands after the conversation is over.
Users often find themselves unable to complete a call or switch to speaker because the touch layer temporarily stops reading touches because of sensor locking, which causes irritation and creates a sense of device failure, although in most cases it is a software failure or sensor contamination. In this article, we will discuss in detail the mechanics of the approach sensor, the reasons for its incorrect operation and methods for fixing this problem.
The approach sensor in the Redmi 9T
The screen responds to your actions in a special module known as the proximity sensor. In the Xiaomi Redmi 9T, this sensor is usually located at the top of the front panel, often hidden under a protective glass next to the speaker, and its task is to emit infrared light and read its reflection from objects. When you bring the phone to your head, the light is reflected, and the system receives a signal to lock the screen.
Sometimes the software misinterprets the data coming from that sensor, and it can be due to calibration or conflicts with the applications installed. It's important to understand that the hardware is working properly, but the logic of decision-making can malfunction, which is why the screen goes out even when the phone is lying on the table or in your hand at a distance from your face.
Technical details of the IR sensor
It's worth noting that in some cases the screen itself is functional, but the background processes block it from turning on. For example, if the Phone application is getting stuck in the background, it may not correctly transmit the call status to the display power management system, which creates the illusion that the sensor is broken, when in fact only a software reboot of the call service is required.
Effect of protective films and covers on the sensor
One of the most common but common reasons why a phone's screen goes out when called is to use poor-quality accessories. Security films or glass that don't have a special cutout for the proximity sensor can distort infrared radiation. Even minimal pollution or an air bubble in the upper end of the Redmi 9T can create a disturbance that the system perceives as an object approaching.
High-sided cases can also block access to the sensor. If you use a thick silicone case, make sure it doesn't cover the top of the display. Often users don't even notice that the edge of the case hangs slightly over the sensor area, creating a permanent shadow for the infrared emitter, as a result, the screen goes out immediately after dialing.
💡
Use full-coverage security glass only if it is guaranteed to be compatible with Xiaomi sensors, preferably with a cutout glass at the top or a special glass for the Redmi 9T, which takes into account the geometry of the sensors.
In addition to physical obstacles, static electricity can cause the problem, accumulating on the surface of a cheap protective glass, which creates an electric field that interferes with the capacitive layer and the optical sensor. Rubbing the screen with a microfiber can temporarily remove the static, but the best solution is to replace the accessory with a better analogue.
Software calibration of the sensor through the engineering menu
If physical obstacles are eliminated, you need to check the software calibration. There is a hidden engineering menu in the MIUI shell that allows you to test and reconfigure the hardware components. It uses a special code to enter it that allows you to access diagnostic tools. This is the first step to take if the screen goes out for no apparent reason.
To get into the test menu, open the Phone app and dial the combination ##6484##. Once you enter the last digit, the CIT (Customer Information Test) interface will open. In the test list, find the "Proximity sensor." When you click on it, you will see the current sensor readings. Close the top of the screen with your hand - the value should change from 5.0 to 0.0 (or vice versa, depending on the software version). If the values do not change or change randomly, calibration is required.
☑️ Testing the sensor in CIT menu
Inside the test, a "Calibrate" button is often available. When you click on it, follow the instructions on the screen: usually remove your hand, press OK, then close the sensor and press OK again. After successful calibration, the system remembers new sensitivity thresholds, which often resolves the problem when the screen goes out too early or does not turn on after a conversation.
System settings and resetting of application parameters Phone
Sometimes the failure is not in the sensor itself, but in the cache of the app responsible for the calls. Accumulated temporary files can cause conflicts that make the phone screen behave unpredictable. Clearing the data and cache of the Phone application is a secure procedure that does not delete your contacts or call history, but resets the interface settings and logic of the call.
To do this, go to Settings → Applications → All applications. Find the list "Phone" (or "Calls"), click on it and select "Clean". Then select "Clear cache" and "Clear all data." After that, restart the device. This procedure eliminates software errors accumulated during operation.
⚠️ Note: Before clearing your data, make sure you remember your Google account or Mi Account password if the system suddenly requests it after resetting your settings, although it is rarely required to clean up the Phone app alone.
It's also worth checking the Pocket Mode settings.This feature is designed to prevent accidental taps, but on the Redmi 9T it sometimes works too aggressively. If you have pocket mode on, try turning it off in screen or lock settings.This can remove false positives when the phone is in your bag or pocket, but the screen keeps going out or on.
Third-party application conflicts and safe mode
Third-party applications, especially those that manage calls, record conversations, or have access to a microphone, can intercept the proximity sensor. If you installed a new software recently, and then the phone screen goes out when you call, the problem may be that popular voice recorders and instant messengers often require access to hardware sensors, which causes conflicts.
To diagnose, run your smartphone in Safe Mode, which only activates system applications. If the problem is gone in Safe Mode, it means that one of the apps you installed is to blame. To enter this mode, press the off button, and when the off icon appears on the screen, click on it and hold your finger for a few seconds until you are prompted to go to Safe Mode.
If the Xiaomi Redmi 9T is doing well in Safe Mode, start removing newly installed apps one at a time, checking the sensor after each deletion. Pay special attention to memory cleaners, antiviruses and alternative calls, which are often the source of system instability.
Table: Comparison of methods of solving the problem
Below is a comparative table of methods that will help if the screen of the phone goes out. Choose the right option depending on your situation and level of technical training.
| Method of decision | Difficulty | Efficiency | Risk of data loss |
|---|---|---|---|
| Cleaning the sensor and filming | Low. | High (if the cause is mud) | No. |
| Calibration via CIT menu | Medium | High (for software failures) | No. |
| Resetting the settings of the phone application | Low. | Medium | No (contacts retained) |
| Full reset (Hard Reset) | Tall. | Maximum | Yes (all removed) |
As you can see from the table, it's always the least invasive way to start, and full flashing or factory resetting is extremely rare, and only if a software failure affects the entire MIUI system, and simple calibration or sensor cleaning helps 90% of the time.
Hardware malfunctions and sensor repair
If none of the software methods worked and the screen continues to go out chaotically, it may be a hardware breakdown. In the Redmi 9T, the proximity sensor can fail due to impact, moisture or production defects. In such cases, the software calibration either fails or gives a temporary effect that disappears after the reboot.
A common hardware problem is the outflowing plume of the display or the sensor module inside the case. When the phone falls, the connector could move slightly away from the motherboard. This requires disassembling the device and reconnecting the plumes. It is not recommended to do this yourself if you do not have experience, since it is easy to damage fragile plumes or break the tightness of the case.
⚠️ Warning: Attempting to repair the hardware part of the phone under warranty will result in loss of warranty obligations. If the device is new, contact an authorized service center.
It's also worth checking if the sensor contacts have oxidized, and if the phone has been in contact with moisture, even as vapor, the contacts could have been plaqueed to prevent transmission, and the service center would have the board washed with ultrasound and replaced with the sensor if it was really defective, which would ensure that the phone screen would work smoothly.
💡
If after calibration and resetting the problem persists, and CIT-The sensor displays constants or zeros regardless of the position of the hand, a direct sign of a physical breakdown of the module.