Approximation Sensor on Xiaomi Redmi Note 9: how to turn on, configure and check

The Xiaomi Redmi Note 9 is one of the most popular smartphones in the budget segment, but even it sometimes has problems with sensors. The proximity sensor is responsible for turning off the screen during a conversation, preventing accidental tapping of the cheek or ear. If it does not work, this leads to inconvenience: the screen goes out on its own or, conversely, remains active, consuming charge and responding to touch.

In this article, you will find step-by-step instructions for turning on the proximity sensor, how to diagnose it and solve problems, where this feature is located in the MIUI settings, how to activate it manually and what to do if the sensor does not respond, and how to check its operation using hidden menus and third-party applications.

What is a proximity sensor and why you need it

The proximity sensor is a small infrared sensor located next to the front camera of a smartphone, and its main task is to detect when you bring the phone to your ear during a call. When it is triggered, the sensor sends a signal to the system, and the screen automatically turns off to avoid accidental taps.

On the Xiaomi Redmi Note 9, this sensor is also involved in:

• 📞 Automatically lock the screen when talking (saves battery power).
• 🔒 Preventing false alarms of touch buttons.
• 🎧 Optimization of work with the headset (for example, when using headphones with a microphone).
• 🔄 Activation of the "In your pocket" mode (if supported by firmware).

If the sensor is not working, you may encounter:

• ❌ Disconnecting the screen during the call.
• ❌ Inability to unlock your phone after a conversation.
• ❌ Fast battery discharge due to constantly active display.

⚠️ Attention: On some firmware MIUI The proximity sensor may conflict with navigation gestures. If you have lags after activating the sensor, try turning off full-screen gestures in Settings → Display. → Full screen mode.

Where is the proximity sensor on the Redmi Note 9

Physically, the proximity sensor on the Xiaomi Redmi Note 9 is located at the top of the screen, next to the front camera and light sensor, and cannot be seen with the naked eye, since it is hidden under the protective glass, but its position can be determined by a small hole or point to the left of the camera (when you look at the screen).

The programmed management of the sensor is carried out through:

• 📱 Basic system settings (Section "Screen" or "Special features").
• 🔧 Hidden Engineering Menu (for diagnostics).
• 🛠️ Third-party applications (such as Phone Tester or Sensor Box).

If you are not sure if the sensor is working, you can check it with a test call:

1. Call another phone.
2. Hold the Redmi Note 9 to your ear.
3. The screen should go out in 1-2 seconds.
4. Take the phone away, the screen will light up again.

How to turn on the proximity sensor through the MIUI settings

In most cases, the proximity sensor on the Xiaomi Redmi Note 9 is activated by default, but after resetting, updating the firmware or manually turning it off, you can do this through the standard MIUI menu.

Instructions for activation:

1. Open the settings (cog icon on the desktop).
2. Go to the Screen section.
3. Scroll down and find Auto Lock or Proximation Sensor (depending on the MIUI version).
4. Activate the switch next to Turn off the screen when approaching.
5. Save the changes and restart the phone (recommended).

If your version of MIUI doesn’t have a separate point for the proximity sensor, try an alternative path:

1. Go to Settings. → Special facilities.
2. Select Physical buttons or System settings.
3. Find the approach sensor option and turn it on.

Make a test call|Put the phone to your ear (the screen should go out)|Put your phone away (the screen should be turned on)|Check the settings in the "Screen" section"-->

⚠️ Note: Some custom firmware (e.g. LineageOS or Pixel Experience) may have different paths to sensor settings. If you use unofficial software, refer to your firmware documentation.

Checking the sensor through the engineering menu

If the proximity sensor doesn't respond to the settings, it can be tested through an engineering menu, which is suitable for diagnosing hardware malfunctions.

Instructions for entering the engineering menu:

1. Open the Phone app.
2. Enter the combination: ##4636###.
3. In the menu that opens, select Phone Information (or Testing).
4. Scroll down and find the Sensors section.
5. Click on the Proximity Sensor.
6. Raise your hand to the top of the screen – the value should change from 5.0 cm to 0.0 cm.

Alternative method (for some versions of MIUI):

1. Enter the phone app: ##6484##.
2. Select the Proximity Sensor Test.
3. Follow the instructions on the screen.

If the sensor does not respond in the engineering menu, the problem may be:

• 🔌 Hardware malfunction (damaged plume or sensor itself).
• 📲 Software failure (resetting or flashing required).
• 🛡️ Blocking from the firmware side (for example, after rooting).

Troubleshooting: The sensor is not working

If the proximity sensor doesn’t work, try the following ways to solve the problem:

1. Phone reboot

Sometimes you just have to reboot the device to make the sensor work. Press the power button and select Reboot. After you turn it on, check the sensor with a test call.

2. Cleaning the system cache

Go to Settings → Applications → Application Management, find the Phone and clear the cache. Also clear the cache in Settings → Memory → Clean up.

3. Resetting settings to factory

If the problem persists, do a soft reset (without deleting data):

1. Go to Settings → About the phone → Reset settings.
2. Select Reset all settings (do not delete all data!).
3. Confirm the action and wait for the reboot.

Checking for physical injuries

Look at the top of the screen for:

• 🔍 Cracks or chips near the front chamber.
• 💧 Traces of moisture (oxidation of contacts).
• 📱 Defragments of protective film (can block the IR sensor).

⚠️ Warning: If the sensor stopped working after a phone drop or water hit, don't try to disassemble the device yourself.In Xiaomi Redmi Note 9, the soldering sensor approaches the motherboard, and its replacement requires soldering equipment.

5. Firmware update

Sometimes sensor bugs are fixed in newer versions of MIUI. Check for updates:

1. Go to Settings → About the phone → System update.
2. Click Check for updates.
3. If a new version is available, download and install it.

💡

If the sensor still does not work after the update, try to roll back to the previous version of MIUI. To do this, download the necessary firmware from the official Xiaomi website and thread it through Recovery or Fastboot.

Third-party applications for sensor diagnostics

If standard methods don't work, use specialized sensor testing tools to show real sensor values and help detect faults.

Top.-3 approximation:

1. Sensor Box for Android Shows all the sensors on the phone, including proximity, light and accelerometer. There's a graph of real-time value changes.

How to use the Sensor Box:

1. Download the app from Google Play.
2. Open it and go to the Proximity tab.
3. Put your hand to the top of the screen.
4. If the sensor is in good working order, the value will change from Far (far) to Near (close).

If the app shows No sensor or the values do not change:

• 🔄 Try reinstalling the app.
• 📱 Check whether the sensor is blocking the protective glass or case.
• 🛠️ Contact the service center (possible hardware breakdown).

💡

If the proximity sensor doesn't respond in settings, in the engineering menu, or in third-party applications, there's a 90% chance that the problem is hardware, and you need to change the sensor or the plume.

Frequent questions about the proximity sensor on the Redmi Note 9