Adjustment of the proximity sensor on Xiaomi Redmi Note 9

The problem with the incorrect operation of the touch screen during a conversation is familiar to many owners of Xiaomi smartphones. The screen either goes out too early, preventing the call from being completed, or, conversely, does not respond to the device’s lift to the ear. Owners of the Redmi Note 9 model often face similar failures due to the design and software of MIUI. The main culprit of this behavior is the proximity sensor, which requires proper calibration or physical cleaning.

This can be caused by software failure after the system update, as well as banal contamination of the upper part of the case. Often users are unaware that the engineering menu of the device is hidden powerful tools to diagnose and adjust this component. Ignoring the problem leads to accidental cheek pressing during a conversation, which can interrupt the conversation or trigger unwanted functions.

The following guide will help you fix the problem yourself without going to the service center, and we will look at software resetting methods, manual calibration through a hidden menu and how to physically maintain the sensor, carefully following all the steps will return the phone to normal operation and comfort when communicating.

Principle of operation and location of the sensor

Modern smartphones, including the Redmi Note 9, use an optical sensor paired with an infrared emitter, which is located at the top of the display, often hidden under a layer of glass in the area of the speaker, and is based on the reflection of infrared rays from objects in close proximity to the screen.

When you hold the phone to your ear, the emitter emits a signal that bounces off the head and returns to the receiver. The processor instantly processes this signal and tells the system to turn off the touchscreen and turn off the display to save energy and prevent false presses. If the distance increases, the screen lights up again.

⚠️ Warning: A low-quality protective glass or film that does not have a special cutout or lack of transparency in the sensor area can block the IR signal.

Diagnostics through the Engineering Menu

The first step to detect the problem is to check the sensor’s health through the built-in CIT engineering menu, which allows you to see the real state of the sensor without third-party applications. To enter the menu, you need to open the standard Phone application and enter a special command.

Type ##6484#. If the code is entered correctly, the hardware testing menu will open. In the settings list, find Proximity Sensor or Approximation Sensor. Click on it to go to the test.

So in the test, you'll see numerical values and a color indicator, and when your hand closes the top of the screen, the value should change, and the indicator should turn green, and if there's no reaction, or the values jump randomly, you need to calibrate or clean.

⚠️ Warning: Don't leave the engineering menu until you've completed all the tests.Accessally pressing the back button can reset the progress of checking other important system components.

Manual sensor calibration process

If the diagnosis has shown unstable work, you need to conduct a calibration procedure.This action resets the current sensitivity thresholds and sets new reference values for your particular instance of the Redmi Note 9.

When you're in the proximity sensor test menu, press the Calibration button. The screen can blink or emit an audible signal. At this point, it's important that there are no objects in front of the top of the phone. The distance to any objects should be at least 50 centimeters.

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Before calibrating, wipe the top of the screen with a dry soft cloth. Even subtle fat spots can knock down sensitivity settings during sensor training.

After pressing the calibration button, the system automatically measures background light and infrared radiation levels, a process that takes a few seconds to complete, and successful completion is confirmed by the appearance of a corresponding message or change of status to "Pass." If you see the word "Fail", repeat the procedure, making sure that there is no interference.

Physical cleaning and maintenance

Often software methods do not help if the problem lies in physical contamination. In the area of the sensor accumulates dust, skin fat and pile from pockets. Redmi Note 9 is characterized by the location of the sensor under the glass, but dirt on the surface or in the grid speaker can critically affect the work.

Use a microfiber lightly soaked in alcohol or a special device for screens. Gently wipe the top of the front panel. Pay special attention to the narrow slit of the speaker, as there is often a fine dust that blocks the path of IR rays.

To clean hard-to-reach areas, you can use a soft brush or a can of compressed air. Blow carefully so as not to damage the speaker membrane. After cleaning, be sure to repeat the calibration procedure described in the previous one!

System settings and software updates

Sometimes the sensor malfunction is associated with an error in the MIUI operating system. Check for available updates in the Settings → About Phone → MIUI version. Developers often release patches that fix the sensor drivers.

Also, check the special features settings. Go to Settings → Advanced Settings → Special features. Make sure that features that can intercept sensor control, such as Handless Control or third-party launchers, are not activated.

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Updating the system to the latest stable version often solves software driver conflicts that cause incorrect operation of the proximity sensor.

If the problem occurs after installing a particular application, try to remove it or check its permissions.Some call programs or voice recorders may take precedence over the system settings of the sensor, causing hardware conflicts.

Solving problems with protective accessories

Security glass and film are a common cause of sensor problems on the Redmi Note 9. If the accessory is black or not transparent enough at the top, it physically blocks the IR radiation, the sensor “thinks” that the object is in front of it, and extinguishes the screen.

Check if the cutout in the protective glass matches the location of the sensor. If the glass frame enters the sensor area, it should be replaced with a model marked "Full Coverage compatible" or "Sensor compatible".

⚠️ Warning: Do not attempt to cut a hole in the protective glass yourself. This will cause chipping and may damage the display itself during further use.

Also, look at the cases. Some cases have high sides, which when you hold the phone in your hand can cover the upper end, in which case the sensor will constantly receive a signal of approach.

Alternative methods and resetting settings

If none of the above methods worked, you can try resetting your phone to factory settings.This is a radical method that deletes all user data, so be sure to back up important information before you start.

To reset, go to Settings → About Phone → Settings Reset → Erase all data. Once the phone is restarted, it will return to its original state and all system errors, including sensor settings, will be fixed.

In rare cases, the problem is hardware-based, with the sensor plume moving away from the motherboard or physically damaging it, and if the phone falls or falls into the water, you can't do without disassembling and replacing the component at the service center.

Frequently Asked Questions (FAQ)