The proximity sensor problem on Xiaomi smartphones is often a source of serious discomfort during conversations. Owners of the popular Redmi Note 9 model often face a situation where the screen does not go out when you bring the phone to your ear, or, conversely, goes out too early, which leads to accidental cheek tapping, resetting calls or turning on the speakerphone at the most inopportune moment.
The reason is that software malfunctions calibration or contamination of the sensor hidden under the top of the display. Fortunately, the MIUI shell has built-in tools to diagnose and fine-tune this component without the need to flash the device. In this article, we will discuss how to calibrate yourself and fix software errors.
Before we get to the complex settings, we need to make sure that the problem is software-based, not physical damage, sometimes just wipe the top frame or remove the protective film if it overlaps the sensor element, but if external factors are excluded, you will need to interfere with the hidden settings of the system.
Diagnostics and check of sensor performance
The first step before any adjustment is to be thoroughly diagnosed, because Xiaomi smartphones have a special engineering menu that allows you to check the response of all hardware modules, which does not require super-user permissions to access, just enter a special code in the call app, which is the most reliable way to know whether the system sees the sensor itself and whether it responds to your actions.
Open the standard "caller" and dial the combination ##6484##. Immediately after entering the last digit, the CIT menu will open. In the list of tests, you need to find the item associated with the Proximity Sensor. Click on it and you will see two values: Near (close) and Far (far). Close the top of the screen with your palm - the value should change, and the indicator should light up green.
⚠️ Attention: If the sensor in the engineering test does not respond to the approach of the hand or shows constant jumps in values even in a stationary state, the problem may be hardware, in which case the software calibration will not help, and you will need to replace the plume or module in the service center.
It's also important to check if the sensor is in conflict with the safety glass or the case. Cheap films often have opaque edges that overlap the infrared emitter. Take off all the security accessories and repeat the test. If the values stabilize, the cause is found. If the test is successful, but in real life the screen is acting strangely, we move to calibration.
It’s also worth checking if Pocket Mode is included in the lock settings, as it uses proximity sensor data to prevent accidental taps, which sometimes causes false alarms.
Calibration through the Proximity Sensor Engineering Menu
The main method of fixing software failures is manual calibration through the same CIT menu that we used for the diagnosis, which causes the system to re-remember the reference values "close" and "far away." The procedure requires accuracy and execution of all the steps in a certain sequence, otherwise the result may be the opposite of what you expect.
When you're in the test menu, select Proximity Sensor. You'll see the Calibration button. Before you press, make sure the front camera and top of the body are completely free of foreign objects. Press the calibration button and wait until the process is complete. The system automatically records the new sensitivity settings.
☑️ Checklist of correct calibration
Once the calibration is completed successfully, it is imperative to restart the device. Without rebooting, the new settings may not apply correctly, and the phone will use old, erroneous data. Once the smartphone is turned on, test again in the engineering menu to make sure the values are written correctly.
In some versions of MIUI firmware, you may need to repeat the calibration procedure 2-3 times in a row to fix the result, this is especially true if the sensor has previously been working incorrectly for a long time and the system is “accustomed” to erroneous readings.
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CIT calibration is the most effective software method, solving the problem in 90% of cases without losing user data.
Sensitization through hidden commands
If standard calibration didn't work, you can try changing the sensor sensitivity threshold. Android systems that run the Redmi Note 9 have hidden parameters that regulate the strength of the signal needed to actuate, which is especially useful when the sensor is either too tight or triggered by the slightest movement of the hand.
To access the advanced settings, enter dialer code ##72626##. This code opens the field test menu. Find the section associated with Proximity Sensor. Here you can see the current settings and, in some cases, change them. However, be careful: changing the digital values without understanding the physics of the process can lead to complete failure of the function.
A safer method is to use ADB (Android Debug Bridge) commands via a computer, which requires connecting the smartphone to the PC and having the driver installed. Commands allow you to interact directly with sensor configuration files. Example of a command to reset the sensor settings:
adb shell settings put system proximity_sensor_default_state 1Also worth paying attention to system updates. Xiaomi engineers often release patches that fix sensor algorithms. Go to Settings → About Phone → MIUI Version and check for updates. Sometimes the problem is solved simply by installing the current version of the software, where the driver is optimized.
What happens if the ADB teams don’t work?
Influence of protective glasses and accessories
One of the most common reasons for the proximity sensor to malfunction on the Redmi Note 9 is the wrong security accessories, which involve placing the sensor in a very narrow area above the speaker, and any obstacle, even a translucent one, can distort the signal.
Cheap security windows often have a black perimeter frame that the phone manufacturer doesn't have, which blocks the infrared beam, so the phone thinks it's in the ear all the time, and it turns off the screen as soon as the call starts, and the solution is to replace the accessory with a model with a sensor cutout or a transparent area on top.
Thick magnetic-clasp bookcases can also affect magnetic sensors, which sometimes work in conjunction with a proximity sensor for the smart case function. If you notice a problem after installing a new case, try removing it and checking your phone.
| Accessory type | Probability of failure | Recommendation |
|---|---|---|
| Transparent film | Low. | We can leave. |
| Black-framed glass | High (90%) | Replace or cut the frame |
| Magnet-book case | Medium | Turn off the cover mode in the settings |
| Hydrogel film | Low. | We can leave. |
If you don't want to change your favorite safety glass, you can try software to turn off the sensor (more on this below), but this will deprive you of the convenience of automatically turning off the screen during a conversation. In the long run, it is better to use accessories designed specifically for your model with the location of the sensors.
Resetting and software error elimination
When neither calibration nor replacement of accessories helps, it is worth considering the option of software conflict: third-party applications, especially those that manage calls, contacts or memory cleaning, can intercept the control of the sensor, in which case the effective solution will be to reset the settings of the phone application and the entire system to factory parameters.
To start, try clearing the data from only the system applications that are responsible for communication. Go to Settings → Apps → All apps. Find the Phone app (green handset icon) and Google Play Services. Go to each of them, select Memory and click Clear. This won't delete your contacts, but will reset your call settings.
If the problem persists, a full Hard Reset may be required.Caution: this step will delete all your data, so be sure to back up.After the reset, the phone will return to the "out of the box" state and any software errors will be corrected. Often it is the "junk" in the system after multiple MIUI updates that causes unstable iron operation.
In rare cases, the problem lies in a specific firmware update. If you recently updated and problems started right after that, it makes sense to search for feedback from other Redmi Note 9 users on forums. It may be a known bug of a particular version of MIUI, and it is better to wait for the next patch or roll back to the previous version.
Hardware malfunctions and repairs
If all software methods are exhausted, and the test in the engineering menu shows no reaction, most likely there is a physical failure. The proximity sensor in the Xiaomi Redmi Note 9 is integrated into the display plume or is in a separate module next to the speaker.
A sign of hardware failure is often a constant “close” signal, even when there is nothing in front of the screen, or a complete lack of response to any action, in which case only a replacement component will help. In service centers, either the sensor plume (if it is separate) or the entire display module is assembled, because in modern smartphones these elements are tightly integrated.
⚠️ Attention: Self-disassembly Redmi Note 9 requires special tools and skills. the back cover is glued, and the plumes are very thin. Inept intervention can damage the display or battery. If you are not confident in their abilities, you better contact the professionals.
The cost of repairs usually depends on whether you need to change only the sensor or the entire screen. In some cases, the wizards offer a service of soldering the sensor, which is cheaper than replacing the display. However, given the design of this model, it is often more cost-effective to replace the entire module to ensure that the image is leaky and quality.
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Before going to the service center, take screenshots of the test results from the engineering menu, which will help the master to diagnose the problem faster and avoid unnecessary questions.