Why Xiaomi Redmi Note 9 is not blocked when calling – all the reasons and ways to eliminate

Have you noticed that during a phone conversation, the screen of the Xiaomi Redmi Note 9 remains active, although it used to be automatically locked? It's not just a minor inconvenience - battery drains, casual touches interrupt the call, and in the worst cases, it can signal serious malfunctions. In this article, we will analyze all possible reasons why the smartphone stopped blocking when calling, and give step-by-step solutions - from simple settings to hardware repairs.

The problem is not only for the Redmi Note 9, but also for other Xiaomi models based on MIUI. However, this model has specific “pain”: incorrect operation of the proximity sensor, conflicts with the shell after updates, as well as a hardware defect in the contacts of the sensor plume, which manifests itself over time due to wear and tear of the mechanism. We will not limit ourselves to general tips – we will analyze each scenario taking into account the features of this model.

1. The proximity sensor: how it works and why it "goes blind"

The main reason the Redmi Note 9 doesn't lock the screen during a call is because the proximity sensor malfunctions, and it's located at the top of the screen (near the speaker) and it's responsible for turning off the display when you hold the phone to your ear, and if the sensor doesn't work, the system doesn't "understand" that you're talking, and the screen stays on.

On the Redmi Note 9, the proximity sensor is combined with the light sensor (they are in the same module).

• 📱 Module pollution: Dust, sweat or cosmetics get into the gap between the glass and the case, blocking the infrared signal.
• 🔧 Weakening of the plume contacts: over time, the sensor connector oxidizes or moves away from the board (especially after falls).
• 🤖 Calibration failure: after update MIUI or resetting the sensor may require reconfiguration.
• 💥 Physical damage: A crack in the glass in the sensor area or a hit on the top edge of the phone.

You can check the sensor with service code or third-party applications, for example, type in the dialer:

##6484##

This will open the sensor testing menu. Put your hand up to the top of the screen, and if the sensor is working, it will show a green square or Near: 0 cm (close distance) and Far: 5 cm (deleted). If the readings don't change, the sensor will malfunction.

⚠️ Note: Some Redmi Note 9 firmware may not have service code, in which case use the Phone Tester app from Google Play, which shows the status of all sensors, including the proximity sensor.

2. Software failures: from updates to “curved” firmware

If the proximity sensor is working but the screen is still not locked, the problem lies in the software. Xiaomi Redmi Note 9 is especially vulnerable to such failures due to the frequent release of MIUI updates, which are not always optimized for specific models.

Typical programmatic reasons:

• 🔄 Conflict after the update: New versions MIUI 12/13/14 They can “break” the logic of the screen lock.
• 🧹 Resetting: After resetting to factory settings, some sensor parameters are reset to a “default” state.
• 📱 Errors in the system cache: Clogged cache of the application Phone or System UI lead to a hanging of functions.
• 🛠️ Custom firmware: Informal builds (like LineageOS or Pixel Experience) often don’t support sensors properly.

How to diagnose a software failure:

1. Check the MIUI version in Settings → About Phone. If it's a beta (marked with the letter V at the end of the build number), roll back to stable.
2. Run your phone in safe mode (hold the power button → Safe Mode) and if it's locked, it's the third-party app's fault.
3. Delete the cache of the Phone application: Settings → Applications → Application management → Phone → Storage → Clear the cache.

3. Phone Settings: What Could Have Changed Without Your Knowledge

Sometimes the problem lies in incorrect settings that were changed accidentally or after an update. Redmi Note 9 has several "hidden" options that affect the lock screen during the call.

Check the following points:

1. Settings → Screen → Autolock: Must be enabled (recommended value is 5 seconds or 10 seconds).
2. Settings → Additional → Special features → Gesture management: turn off the option to Ignore the proximity sensor (if it is active).
3. Settings → Applications → Permissions → Auto Run: Make sure that the Phone application is allowed to autorun.
4. Settings → Battery and Performance → Battery Mode: If Charge Saving Mode is selected, some sensor functions may be turned off.

Pay special attention to the settings of the application “Phone”:

1. Open the phone application → press ⋮ (three-point) → Settings → During the call.
2. Check if the screen lock option is enabled when approaching (it is called the Approach Sensor on some firmware).
3. Turn off the option to keep the screen on if it is active.

4. Physical damage: when repairs are not necessary

If none of the software methods worked, the problem is likely hardware.The Redmi Note 9 has design weaknesses that cause the proximity sensor to fail:

Self-repair is only possible if you have experience disassembling smartphones. Redmi Note 9 will require:

• 🔧 Setting screwdrivers T3-T5 and mediator.
• 🔥 Hair dryer or a station for heating glue (the body is glued, not on latches!).
• 📱 New approximation sensor plume (article for order: Xiaomi Redmi Note 9 Proximity Sensor Flex Cable).

⚠️ Attention: When disassembling the Redmi Note 9, there is a high risk of damage to the battery plume - it is attached to the motherboard with fragile connectors. If you are not sure about your skills, contact the service: ~1 500–2 500 ₽.

5 Conflicts with covers, films and accessories

Sometimes the problem isn't with the phone, but with accessories that interfere with the sensor, which is especially true for the Redmi Note 9, which has a proximity sensor close to the edge of the screen.

Check the following points:

• 📱 High-sided case: If the case covers the top of the screen, it can block the infrared signal of the sensor.
• 🔄 Security glass or film: poor quality glass with a metalized layer (for example, "mirror" or "private") screens the signal. Take off the glass and check the sensor.
• 🎧 Magnet headphones: Some wireless headphones (like Xiaomi AirDots) have magnets that can affect the sensor.
• 🔋 Power Bank or wireless charging: Strong magnetic fields from accessories sometimes knock sensors down.Remove magnetic radiation sources away from your phone.

If the problem disappears after removing the case or glass, the solution is simple - replace the accessory with a model with a notch under the proximity sensor. For example, cases from Spigen or Ringke for Redmi Note 9 have special notches for sensors.

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Before buying a case, check if it has a cutout at the top – it should match the location of the proximity sensor on your phone.

6. Alternative solutions: if nothing has worked

If all of the above methods fail, there are workarounds that at least partially solve the problem:

• 🔄 Forced button lock: Get used to locking the screen with the power button manually during a call. Inconvenient but secure.
• 📱 Screen locking apps: Utilities like Proximity Sensor Fix or Screen Off and Lock can emulate sensor performance.
• 🔧 Firmware rollback: If the problem has appeared after the update MIUI, Return to the previous version via Fastboot (instruction below).
• 🤖 Reset to factory settings: Extreme measure, but sometimes helps. be sure to make a backup!

To roll back firmware on Redmi Note 9, follow the following steps:

1. Download the desired version of MIUI from the official Xiaomi website (select the Redmi Note 9 model, merlin encoding).
2. Unpack the archive and place the update.zip file in the root of the phone’s memory.
3. Go to Settings. → The phone. → Updating the system → ⋮ (three-point) → Select a firmware file.
4. Select the downloaded file and confirm the installation. The phone will reboot.

⚠️ Note: Firmware rollback erases all data if you are not using Lock’s Data Cleanup feature. Also, after rollback, you may need to re-unlock the bootloader if it was previously unlocked.

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If the proximity sensor is physically fit, but the problem remains — 90 percent of the time, it's the software that's to blame. Start by clearing the cache and resetting the phone app before you resort to drastic measures.

FAQ: Frequent questions about screen locking on Redmi Note 9