Budget smartphone owners often face a situation where the display does not turn off during a phone call, which creates significant inconvenience, since it is easy to press volume buttons, activate call retention or turn on speakerphone, especially for the Xiaomi Redmi 9A model, where the proximity sensor is located in a specific location.
The main reason is that the sensor is not working properly, which should detect the device's lift to the ear. Unlike the flagship models, it uses software emulation or a simplified infrared sensor, and the failure of its operation can be caused by software errors of the MIUI shell, as well as physical contamination or design features.
You can figure out the causes and fix the malfunction yourself without going to the service center. In most cases, only the correct calibration or removal of the inappropriate protective film is required. Below we will discuss all possible scenarios in detail and provide step-by-step instructions for restoring the normal operation of the gadget.
The approach sensor in the Redmi 9A
To understand the problem, you need to understand the technical device. The Xiaomi Redmi 9A uses an infrared proximity sensor, it emits an invisible beam and reads its reflection. If the object (your ear) is close, the beam reflects, and the system receives a command to turn off the display.
But in this model, the sensor is often paired with a speaker or placed on the top of the body without a separate glass window, making it sensitive to the slightest contamination, and calibration is the process of setting thresholds at which the phone knows it's near the ear.
There is also the concept of a "virtual sensor" that works on algorithms for analyzing images from the front camera, but the Redmi 9A uses a classic hardware circuit that depends on the correctness of readings that can be distorted due to software conflicts.
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The proximity sensor in Redmi 9A is in a narrow strip above the screen, and any dirt or fat in that area blocks it from working.
Importantly, even a microscopic crack on the top of the protective glass can scatter the IR beam, which makes the phone think it's always closed or open, which is why accurate diagnosis begins with a visual examination.
Influence of protective glasses and covers
One of the most common reasons why the screen doesn't go out when talking to Xiaomi is because of the wrong protection. Many universal security glasses have a black frame that covers the sensor area. In the Redmi 9A, the sensor zone may not match the cutouts on the film.
If you've recently put on a new glass or installed a thick, high-sided case, the problem may have occurred after that, and the case can mechanically press the sensor area or create a shadow that the sensor perceives as an obstacle.
- 📱 Remove the security glass and check the operation of calls without it.
- 🧼 Carefully wipe the top of the screen with an alcohol fat wipe.
- 🛡️ Make sure the cutouts on the film match the speaker and sensor exactly.
⚠️ Some cheap protective glass does not have a special transparent window above the sensor, but is simply painted in black, which completely blocks IR radiation.
It is also worth considering that over time, the adhesive on the protective film can become cloudy or yellow, especially in the upper part, where the heat is from the speaker and the processor. This gradually reduces the sensitivity of the sensor, requiring the replacement of the accessory.
Software calibration of the sensor
If physical obstacles are eliminated, software calibration is required, the main method of solving the problem when the screen does not go out when speaking on Redmi 9A. MIUI has a hidden engineering menu for testing equipment.
To enter the test mode, open the Phone app and enter a special code. This action is safe and will not lead to data loss. Once you enter the code, the CIT menu will open, where you can check all the modules of the smartphone.
##6484##In the menu that opens, look for the Proximity sensor. You will see a numerical window. Cover the top of the screen with your finger, which should vary (usually from 5.0 to 0.0 or vice versa). If there is no response, press Calibration or Pass after checking.
☑️ Calibration procedure
After successful calibration, be sure to reboot the device completely. Only after activation will the system apply new sensitivity settings. In some cases, the procedure must be repeated 2-3 times to achieve a stable result.
Settings in the Hidden Engineering Menu
Some versions of the Redmi 9A MIUI firmware offer an advanced setting through an engineering menu that allows you to change the trigger thresholds. Be careful that changing the wrong settings can cause other functions to malfunction.
You can get here through the same test menu or through the developer settings, and look for the Proximity section, and you can see the current status and force the test to run.
| Parameter | Normal value. | Description |
|---|---|---|
| Distance | 0.0 - 5.0 cm | Distance to object |
| Raw Data | Changes. | Sensor raw data |
| Status | Near / Far | Current state (close/far) |
If the Status graph is constantly burning Near (Close), even though there is nothing in front of the screen, then the sensor is software-based, only resetting the calibration or cleaning the system cache will help.
What if the code doesn't work?
Cache cleanup and reset settings
System debris often causes driver conflicts, and if the screen doesn't go out during a conversation, it may have been a failure in the system files that process the sensor's signals, and the first step is to clear the cache.
Go to Settings → Apps → All apps. Find the Phone app and Google Play Services. In each of them, select Clear Cache and Clear All Data. Don't worry, contacts and call history won't be deleted, only the app settings will be reset.
- 🗑️ Clear the cache of the "Phone" application".
- ⚙️ Reset the settings of the application "Google Play Services".
- 🔄 Reboot your smartphone.
In extreme cases, if the software failure is critical, a full reset to factory settings helps. Remember that a full reset (Wipe Data) deletes all your photos, contacts and applications, so be sure to back up your data to the Mi Cloud cloud or to your computer.
⚠️ Before you completely reset, make sure the battery is at least 60% charged so that the phone doesn’t turn off during the system recovery process.
Hardware problems and repairs
If software methods, calibration and film replacement didn't work, there's a hardware malfunction. In the Redmi 9A, the proximity sensor plume can move away from the motherboard due to falls or vibrations, and the sensor itself can fail.
Self-disassembly of a smartphone requires skills and tools, you'll need a suction cup, mediators and a set of screwdrivers, and the sensor plume is under the top of the case, next to the battery.
Check the plug connection to the board. Often, it's enough to just reconnect the connector, pressing it tightly until you click, and if the sensor burns, you'll need to replace it with a compatible one.
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If after reconnecting the plume and calibration the problem persists, most likely, the sensor module itself is defective and requires replacement in the service.