The problem of suddenly turning off a screen during a conversation and not being able to complete a call or turn on speaker is familiar to many smartphone owners. It is a classic symptom of a sensor that is not working properly when objects approach. In Xiaomi devices, including the Redmi and Poco brands, this malfunction is common enough due to the features of the MIUI or HyperOS software shell. Usually the system copes with calibration when the device is turned off and on, but sometimes manual intervention is required.
The essence of this component is to emit an infrared beam and read the reflected signal. If the software algorithm is wrong in determining the sensitivity threshold, the phone thinks it's in your pocket or in your ear, even though you're just holding it in front of you. Adjusting the sensor allows you to reset those values by default and make the device reset minimum and maximum values. It doesn't require sophisticated hardware or deep knowledge of programming.
In this article, we will look at all the available solutions, from standard engineering tests to the use of specialized applications. You will learn why the protective glass can interfere with the sensor and how to properly clean the upper part of the case. It is critical not to glue the area above the speaker opaque materials, as this physically blocks the operation of the infrared emitter. Let's take a detailed look at the process of restoring the correct functionality of your gadget.
Principle of operation and causes of failure
The proximity sensor in modern smartphones is a compact module consisting of an infrared LED and a photodetector. When you hold the phone to your ear, the beam reflects off the skin and hits the receiver, which gives the system a command to turn off the display to save energy and prevent accidental cheekstrokes. However, in Xiaomi models with frameless screens or necklines (“ bangs”), the space for this sensor is often limited, making it susceptible to external factors.
One of the main reasons for malfunctioning is software failure in the drivers or the Android operating system itself. After updating the firmware, old calibration data can conflict with new signal processing algorithms. Physical contamination is also a problem, as dust, fat or glue residue from the protective film stuck on the top of the case can distort the readings. Even a microscopic crack on the glass in the speaker zone can scatter the beam so that the sensor will be constantly active.
Sometimes third-party applications that intercept sensors or create background processes that interfere with the normal operation of the phone are the culprits. Antiviruses, memory cleaners or call recording programs can block access to equipment. In rare cases, hardware failure of the module itself is observed, especially if the phone fell or was exposed to moisture.
⚠️ Attention: If after all the adjustments, the screen still goes out spontaneously, check the integrity of the sensor plume. In models with a sensor built into the screen (under the display), mechanical damage to the matrix often disables the proximity system.
Diagnostics through the Engineering Menu
The most reliable and safe way to check and adjust the sensor is to use the built-in CIT (Customer Integration Test) menu, which is available on all Xiaomi devices without the need to obtain superuser rights (Root). To enter the test mode, you must open the standard Phone application and dial a special command. Enter the code # # #6484# or ##4636# in the dial field.
Once you enter the code, you'll see a list of many tests of the various components of the device, and you'll need to find a point called Proximity Sensor or simply Proximity. MIUI This test can be in the Common or Sensor subsection, and if you click on it, you'll see a screen with two numerical values: Raw Data and the current state (Near/Far). In an ideal state, when there is nothing in front of the top of the phone, the value should be 0.0 (And when you put your hand in the palm, change it. 1.0 (Near).
If the values jump or show a constant response even in a clean field, calibration is necessary. The test window usually has two buttons: Calibrate and Pass, the process is simple: you remove all items from the screen, press Calibrate, wait for a few seconds, and then close the sensor with your palm. The system will write down the new thresholds. Once the test is completed, press Pass to save the changes and exit.
Use of the Xiaomi Engineer Mode app
If the standard menu doesn’t open or doesn’t have a calibration feature, you can use the third-party, but time-tested Xiaomi Engineer Mode app, which is available on the Google Play Store and allows you to access hidden diagnostic features. This app is especially useful for older models where standard codes could be blocked by the manufacturer in newer versions of firmware.
Once you install and run the app, you'll be given a list of available tests. Search the Single Item Test list, then select Proximity Sensor. The interface will be different from the standard CIT, but the way it works will remain the same. You'll see a graph or numerical values that change in real time. The main challenge here is to achieve stable state switching when you put your hand in.
Some versions of the app have a forced sensor reboot button, which can help with software-based driver freezes, and you can see the type of sensor you use (e.g., LTR-559 or built-in screen), which is useful for understanding the nature of the malfunction. If the app shows that the sensor is not found or returns errors, this is a sure sign of a hardware problem.
- 📱 Download the official Xiaomi Engineer Mode app from a reliable source.
- 🔍 Start the Proximity Sensor test in the Single Item Test section.
- 🖐️ Check the screen response to the palm lifting and removal.
- 💾 Press the save or calibration button if it is available in the interface.
Secret code for rapid calibration
There is another method that works on most Redmi and Xiaomi devices – it is a direct call to the calibration function through a special device. USSD-Unlike the engineering menu, this method immediately starts the process of resetting the sensor settings without having to click the menu. type on the keyboard ##8778## (if the code doesn't work, try ##3646633## for MediaTek processors).
The Engineer Mode menu will open, where you go to the Hardware Testing tab. Next, select Sensor and find the Light/Proximity Sensor. Here will be the Get one data button to get the current value and the PS Calibration button to start the process. Click on calibration, close the sensor with your finger, then remove your finger and press "Do calibration." The device should vibrate or make a sound to confirm success.
It is important to perform this procedure in good lighting, but without direct sunlight falling on the sensor. Bright light can confuse the calibration, since the infrared receiver is sensitive to the outside spectrum. Once the procedure is completed, be sure to restart the smartphone so that the new parameters take effect in the system.
What do I do if the codes don't work?
Comparison of customization methods
The choice of how you adjust depends on your phone model and the version of the operating system installed. For convenience, we have compiled a table that will help determine the best method for your case. Some are deeper, others are superficial, but fast.
| Method | Difficulty | Efficiency | Risks. |
|---|---|---|---|
| Engineering Menu (CIT) | Low. | Tall. | Minimum |
| Engineer Mode Application | Medium | Medium | Low. |
| Secret Codes (MTK) | Tall. | Maximum | Medium (setting error) |
| Resetting phone settings | Tall. | Tall. | Loss of data |
As you can see from the table, the standard engineering menu is the middle ground in terms of safety and result. Using codes for MediaTek processors gives you more control, but it requires caution: changing unknown parameters in the engineering menu can lead to unstable operation of the radio module or touch screen. So if standard calibration helps, you should not go into deep settings unnecessarily.
If none of the software methods worked, the problem goes deeper, it may require a physical cleaning or replacement of the component, and the table also lists resetting as a last resort — it is effective, but it takes time to recover data and reset the smartphone.
Physical factors and maintenance
Before you blame the software, take a close look at the top of the smartphone.In modern Xiaomi models, the sensor is often hidden under a thin speaker grid or directly under the display glass.Any film, poor-quality security glass or high-sided case can block the sensitivity zone.Make sure there are no foreign objects in the area above the screen.
Cleaning should be done with a soft, slightly moist microfiber. Don't use alcohol or aggressive chemistry directly on the speaker, as liquid can get inside the body and damage the membrane or the sensor itself. Gently wipe the top frame, removing fat deposits that are often left over from phone conversations. Even a thin layer of fat on the glass can work as a lens focusing the beam in the wrong place.
☑️ Check-up before calibration
Also, pay attention to the temperature of the device. When you get hot, the characteristics of the electronic components can change, which leads to false positives. If the phone is hot, let it cool down and check again. During the cold season, condensation inside the case can also cause interference, so avoid sudden temperature changes.
⚠️ Warning: Do not try to disassemble the phone yourself to clean the sensor if you do not have experience.In models with adhesive screen connection, there is a high risk of damaging the plume or breaking the matrix when opening.
Radical measures and resetting settings
If all of the above methods fail, the last software option is a full reset (Hard Reset), which will delete all your data, apps and photos, returning the phone to the “out of the box” state. Often it is conflicting system settings or errors in the Android registry that prevent the sensor from working correctly, and a clean installation of the system solves the problem.
Before you reset, make sure to back up your data in the Mi Cloud or on your computer. Don't restore all applications from the backup after the reset. First, check the sensor on the clean system. If it works, it means that one of the installed applications created the problem. Return the programs one by one to find out the culprit.
In cases where even a complete reset doesn't work, it's a hardware problem. The proximity sensor is a physical component, and it tends to fail. Xiaomi smartphones often have plume detachment or contact oxidation, and only a visit to an authorized service center to diagnose and replace the module will help.
💡
If calibration and reset didn't work, it's a hardware problem, you need to clean the contacts or replace the sensor in the service.