Poco smartphones, particularly the popular M3, are often the focus of attention when faced with a screen malfunction during a call. The main reason for complaints is when the display does not go out when you hold the device to your ear or, conversely, switches off in your pocket. To effectively solve this problem, you need to clearly understand where the proximity sensor is physically located and how it functions in the design of this particular device.
Unlike older models, where the sensor was placed in a separate hole above the screen, the Xiaomi Poco M3 engineers have applied a more modern, but demanding solution: the touch element is hidden under the protective glass at the top of the front panel. This means that any contamination, greasy fingerprints or poor-quality protective film can become a critical obstacle to its operation, causing false alarms of the system.
Understanding the exact location of this component is the first step to diagnostics, and if you know where to look and what to wipe, you can fix 80 percent of the software and physical failures without going to the service center, and we'll go into detail below about the top-body architecture and how to check the sensor's health.
⚠️ Before you start any cleaning or diagnostic manipulations, make sure the device is turned off or at least unlocked so that accidental touches do not lead to unintentional actions in the interface.
Physical location of the sensor on the body
The front of the Poco M3 smartphone has no visible holes or cutouts in the speaker area, which is typical of the hidden placement technology. The proximity sensor is integrated directly under the black bezels at the top of the central part of the screen, next to the conversation speaker and the front camera. Visually, this area is a glossy black strip that merges with the display off.
Structurally, the element is less than a millimeter away from the inner edge of the protective glass. This arrangement requires perfect glass transparency at that particular point. If you use a protective glass with a black frame that covers the active zone of the sensor, it is guaranteed to cause it to fail. Accessories manufacturers do not always take into account the exact tolerances, so the choice of film plays a crucial role.
Importantly, you can have a light sensor next to the main IR sensor, and they often work in pairs, but they're responsible for different functions: one turns off the screen, the other controls the brightness. At Xiaomi Poco M3, they're grouped into one module, so pollution on the top affects both functions at once.
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Use a microfiber and a small amount of isopropyl alcohol to clean the speaker zone – this will remove the fat film, invisible to the eye, but blocking the IR ray.
Principle of operation and causes of failure
The technology used in this smartphone is based on infrared radiation, and the sensor constantly emits an invisible beam and analyzes its reflection from nearby objects. If the beam is reflected from the ear or cheek, the system receives a signal that the phone is in the face, and turns off the touchscreen, a failure in this chain can be caused by both MIUI software and physical factors.
One of the common causes is software conflict: the operating system may not properly process the data coming from the sensor, especially after updating the firmware. In such cases, even a clean screen does not guarantee proper operation, because the calibration may be confused, the system begins to ignore the real readings or, conversely, assume that the object is always nearby.
Physical damage also plays a role, and a fall in a smartphone could have caused a plume to detach or a microcrack in the sensor module itself, and unlike software errors, it requires hardware intervention, but software failures and contamination should be avoided before carrying the phone for repair.
Why does the sensor work again?
Diagnostics with the help of engineering menu
To accurately determine the status of the sensor in the MIUI shell that Poco runs on, there's a built-in diagnostic tool that lets you see if the sensor is seeing an object at the moment, and it's the most reliable way to distinguish a software glitch from a physical breakdown or contamination.
To get into the test menu, open the Phone app and enter a special code. Once you enter the last digit, the menu will open automatically. Find the item associated with the proximity sensor check. During the test, the screen can flash different colors, and the sensor will respond to the top of the palm closing.
☑️ Checking the sensor in the engineering menu
If the distance does not change during the test when the hand closes the top of the screen, this indicates a problem. In the normal state, when there is nothing in front of the sensor, the value should be maximum (usually 5.0), and when the object approaches, the value should fall to 0.0.
| Parameter of the test | Normal value. | Value in case of malfunction | Possible cause |
|---|---|---|---|
| Distance (Distance) | 5.0 (no object) | 0.0 (continuing) | Pollution, film. |
| Distance (Distance) | 0.0 (object nearby) | 5.0 (continuing) | Flaw, plume drop. |
| Color Test | Change. | It doesn't change. | Driver error |
| Response Time | < 0.5 seconds | > 2 seconds | High CPU load |
Methods of calibration of the sensor
If the diagnostics show that the sensor is responding but is not responding correctly (e.g., the screen goes out too soon or too late), a forced calibration is required. In some versions of MIUI firmware, this feature is available directly in the engineering menu after passing the test.
When the standard menu is not helpful or hidden by the operator, users resort to third-party apps from the Google Play Store.Proximity Sensor Reset/Fix allows you to reset the sensor to factory values. However, it is worth remembering that such applications require root rights for deep calibration, although the basic reset can work without them.
An alternative is to use ADB (Android Debug Bridge) over a computer, which is more complex but effective in severe software failures, and allows you to send a command to reset the sensor configuration at the system level, bypassing the interface constraints.
adb shell settings put system proximity_sensor_initial_calib 0Once the command is executed, it is necessary to restart the device, and if the software calibration has not yielded results, there is a high probability that the problem lies in the physical state of the surface or the module itself.
Influence of accessories and protective glasses
The most common cause of sensor problems on the Poco M3 is security accessories, which many users buy cheap, wide-black-framed protective glass to protect the screen, often overlying the area where the hidden sensor is located, blocking infrared radiation.
Even if the glass is transparent but has low IR transmittance, the sensor will not work smoothly, and a thick glass or glass with a low-quality oleophobic coating can distort the angle of reflection of the beam, causing the phone to "think" it's lying on the table, even though it's near the ear, or vice versa.
To test the effect of the accessory, remove the protective glass or film and repeat the test in the engineering menu. If the problem has disappeared, the solution is found - you need to replace the accessory with a better one, with a cutout for the sensor or with guaranteed compatibility. Don't skimp on screen protection if this leads to discomfort when using.
⚠️ Warning: Some types of liquid glass or polymer films can create a “lens” effect by focusing IR rays and causing false positives even without overlapping the sensor.
Software solutions and resetting settings
When physical factors are ruled out, it remains to look for the cause in software: Conflicting applications, especially those that manage calls, contacts or have access to sensors, can block the sensor from working.
Resetting all settings to factory-based (Hard Reset) is a radical but often effective method that deletes all user data and returns the system to its original state, and make sure to back up important data before doing so, as it will be permanently deleted.
It’s also worth checking for system updates. Xiaomi regularly releases patches that fix hardware drivers. Go to Settings → About Phone → MIUI version and check for new versions of the software.
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Comprehensive approach: cleaning the sensor area, removing the protective glass and software reset solve 95% of problems with the proximity sensor without repair.