Poco X3 Pro smartphone owners often face a situation where during a phone conversation the screen does not go out when you bring the device to your ear, or, conversely, goes out at the most inopportune moment. This is a direct indication of the incorrect operation of the sensor responsible for determining the proximity of objects. Understanding exactly where the proximity sensor on the Xiaomi Poco X3 Pro is, is the first step to solving the problem yourself without going to the service center.
In modern smartphone models, including Poco’s flagship lineup, manufacturers have abandoned the physical windows at the top of the screen in favor of integrating sensors directly into the display module. On the Poco X3 Pro, the proximity sensor is hidden under the panel, making it invisible to the user’s eye but critical to the system’s operation. The lack of visible element often leads to confusion when trying to diagnose or sticking protective glasses.
In this article, we will take a look at the architecture of your device’s sensors, how to program them, and how to fix software failures, how to calibrate correctly through the engineering menu, and why thick security glass can cause persistent false alarms, and how to avoid costly repairs with a sound approach to setting up.
Design features and hidden location
The Virtual Proximity Sensor technology used in the Poco X3 Pro uses ultrasonic or optical waves that pass through the display glass. Physically, the element is located in the upper center of the screen, directly under the speaker. Unlike the older models, there is no separate hole or darkened area, which allows you to increase the usable area of the screen and improve the aesthetics of the device.
The principle is to emit a signal and analyze its reflection from objects. When you hold the phone to your head, the signal is reflected and returned to the receiver, after which the power controller is instructed to turn off the lights and touchscreen. However, if an obstacle occurs in the path of the signal, such as dirt or poor quality film, the system can interpret this as the constant presence of an object nearby.
⚠️ Attention: Trying to mechanically locate the sensor on the device body is meaningless, it is fully integrated into the display assembly and has no external manifestations other than a software reaction to your actions.
It's important to understand that sensor sensitivity depends on the quality of the display module itself and the factory calibration. When changing the screen in unskilled services, the resetting procedure is often ignored, which leads to a problem in operation, which is why knowing the location helps to position the device correctly when conducting tests.
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When adhesive glass, choose models with a speaker cutout or special oleophobic coatings that do not distort the sensor signal.
Diagnostics of the sensor through the engineering menu
To accurately determine the location and performance of the element in MIUI and HyperOS, there is a built-in diagnostic tool, accessed through universal code that works on most Xiaomi devices. You do not need to install third-party applications from the store, since the system functionality provides all the necessary information.
To run the test, open the Phone app and dial the combination ##6484##. Once the last digit is entered, the CIT menu will open. In the list of parameters, you will find the "Proximity Sensor" or "Proximity Sensor" item.
☑️ Testing the sensor in CIT
In the test, the screen will change color or display distance values in centimeters. Hold your palm to the top of the screen where the sensor is supposed to be. If the numbers vary from 5.0 cm to 0.0 cm (or close to zero), then the sensor is physically functional and responsive to obstacles. If the values are standing still, the problem may be software or hardware damage to the plume.
| Parameter | Normal value. | Failure value | Description of the state |
|---|---|---|---|
| Distance (Distance) | 0.0 - 5.0 cm | Constant 0.0 or 5.0 | Real distance to the object |
| Status (Status) | Near / Far | Freeze in one mode | Logical state of the sensor |
| Raw Data | It's changing dynamically. | Static number | Raw data from the matrix |
| Calibration | Success | Failed | Results of the last calibration |
Procedure for calibration of the proximity sensor
If the diagnostics show that the sensor is responding but not correctly (e.g., the screen goes out when the phone is on the table), calibration is required. This procedure “trains” the system to understand what is considered a close object and what is a normal background. On the Poco X3 Pro, calibration is often lost after updating the firmware or replacing the display.
To start the procedure, go back to the CIT test menu, select "Proximity Sensor" and press the "Calibrate" button, at which point the screen will ask you to close the sensor. Cover the top of the screen with your palm so that there are no gaps, and hold until there is a vibration or an audible signal. Then remove your hand and wait for the message of success.
⚠️ Warning: During calibration, make sure that the screen is free of dust, greasy spots or cracks in the top, and any contamination will be perceived by the system as a reference state, which will lead to incorrect operation in the future.
In some versions of the MIUI shell, the automatic calibration may not work the first time, in which case it is recommended to repeat the process 2-3 times. If after attempts the system gives an error, you may need to reset all settings to factory, but this is an extreme measure that requires backup data.
What to do if the calibration does not pass?
Influence of accessories and external factors
Often, external factors are not the cause of malfunction. The Poco X3 Pro has a large enough camera and speaker module at the top, which forces users to use three-dimensional cases. Some protective cases have protruding sideboards that partially overlap the sensor's area of operation, causing constant false positives.
Special attention should be paid to protective glass. Cheap analogues can have an opaque black frame or a layer of glue that distorts infrared radiation. If you recently replaced the glass and immediately after that the sensor stopped working, the problem almost certainly lies with the quality of the new accessory, in which case only replacing the glass with original or better one helps.
- 📱 Glass thickness: Glasses that are too thick (more than 0.33 mm) can reduce sensor sensitivity, making it blind».
- 💧 Moisture and dirt: Drops of water or greasy spots in the speaker area block the signal. wipe the screen with a soft cloth before important calls.
- 🧲 Magnetic accessories: Magnetic clasp covers can interfere with the electronic components in the upper part of the body.
Temperature is also important. If the Snapdragon 860 processor is overheated, there may be temporary disruptions to the peripheral sensors, so if the phone is hot, let it cool down and check the sensor again.
Program conflicts and system settings
There are some software errors in the operating system itself. Android has settings that can take control of the sensor. For example, the "Mode in your pocket" function is designed to block random clicks, but its incorrect operation can lead to the screen going out on its own.
Check settings in Settings → Lock and Protection → Mode in your pocket. If the feature is activated, try turning it off and check if the device behavior changes. Also, look at third-party call apps you may have installed from Google Play. They may have their own sensor data processing algorithms that conflict with the system ones.
In rare cases, resetting network and application settings helps. This will not delete your personal photos or contacts, but will return system configurations to their original state. To do this, go to Settings → Advanced Settings → Recovery and Reset → Reset your Wi-Fi, mobile Internet and Bluetooth settings.
⚠️ Warning: Before performing a full reset to factory settings (Hard Reset), be sure to back up all important data, as this procedure will completely clear the internal memory of the phone.
Hardware malfunctions and repairs
If software and calibration methods fail, there is a high probability of hardware failure. In the Poco X3 Pro, the proximity sensor plume is often integrated into the shared charging port plume or goes by a separate thin wire to the motherboard, and when falls or moisture hits, these contacts can oxidize or depart.
It's not possible to replace the sensor on its own, because it's part of the display module in this model. If the CIT diagnostics show zero response or a persistent error, you'll need to replace the entire screen assembly or professionally solder the component at the service center. Cheap displays (copies) often have lower-quality sensors than the originals.
- 🔌 Train escape: After falling, the connector may have detached from inside the enclosure.
- 💦 Oxidation: Moisture ingress causes contact corrosion, resulting in loss of signal.
- 🖥️ Matrix defect: In rare cases, the sensor layer is damaged along with the matrix when impacted.
When you contact the service, be sure to require a test in your presence, the wizard should show the sensor operation in the engineering menu before and after the repair, which ensures that the problem is solved efficiently and you do not have to return with the same malfunction in a week.
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If the sensor shows 0.0 cm without obstacles and does not respond to the hand, it is 99% hardware breakdown that requires repair.