Lock screen when calling Xiaomi Redmi 9C: how to turn on and configure

Xiaomi Redmi 9C is a budget smartphone with decent specs, but some users face a problem: during a phone conversation, the screen does not lock automatically. This leads to accidental button presses, speakerphone activation or even a call reset. In this article, we will discuss how to properly adjust the lock screen when talking, why it may not work, and what to do if the proximity sensor refuses to function correctly.

The problem is most often due to system missets, proximity sensor contamination, or software failures, and in most cases, it can be solved without going to a service center, just follow the instructions you have tested, and we'll look at all the options, from basic settings to hidden MIUI features, and alternative methods for those who have the sensor out of order.

Why the screen doesn't lock when you call Redmi 9C

Before you start setting up, it's important to understand why the crash happened. In Xiaomi Redmi 9C, the proximity sensor, a small sensor next to the front camera, detects when the phone is held to the ear and turns off the touch screen to avoid accidental touch.

The main reasons for incorrect work:

• 🔹 Sensor contamination – dust, greasy traces, or protective film can block the signal.
• 🔹 Software failure - errors in the work MIUI or conflict with installed applications.
• 🔹 Disabled function in settings – sometimes the screen lock is manually deactivated.
• 🔹 Sensor damage – physical breakdown after falling or getting moisture.
• 🔹 Incompatible software – outdated version of firmware or custom recovery.

If the problem suddenly appears, the software is most likely to blame, and if the sensor has never worked correctly, it is worth checking its physical condition. In the next section, we will discuss how to diagnose the malfunction.

How to check the proximity sensor on the Redmi 9C

Before you set up the lock, make sure that the proximity sensor is in good working order, and for that, MIUI has a hidden test mode.

1. Open the phone app and dial the combination: ##6484##.
2. The Manual Test menu will open.
3. Scroll down and select Proximity Sensor.
4. Put your hand to the top of the screen (where the front camera is located).

If the sensor is working correctly, you will see changes on the screen:

• 🟢 Green background and 0 - sensor not closed (phone not in the ear).
• 🔴 Red background and value 1 - sensor closed (phone to the ear).

If you get your hand close, the screen doesn't change color or it doesn't show the right values, the sensor is defective, and if you get a replacement at the service center, if the test is successful, but the locking doesn't work, you can go to the system settings.

💡

If the combination ##6484## doesn't work, try ##4636## → Phone Information → Equipment Testing.

Enable screen lock when calling through MIUI settings

In most cases, the problem is solved by activating the corresponding function in the settings menu. In MIUI for Redmi 9C, the path may differ depending on the firmware version, but the general scheme is as follows:

1. Open the settings (cog icon on the desktop).
2. Go to the Appendix section → Application management.
3. In the upper right corner, press three dots (⋮) and select Special Access.
4. Find the Call Permissions (or Call Configurement) item.
5. Activate the option to Lock the screen when approaching (or the proximity sensor).

If there is no such item, try an alternative path:

1. Go to Settings → System and device → Additional settings.
2. Choose Special Opportunities → Physical buttons.
3. Check for the screen lock option during the call.

After activation, restart your phone and check the function during the test call. If the lock still doesn't work, proceed to the following methods.

Is the option "Blocking at approach" activated"?|Has the sensor been tested?|Reload your phone after the changes?|Checked for lack of protective film on the sensor?-->

Resetting phone settings and sensors

If the settings don't work, it could be a software failure, in which case it might be a reset of sensors or a complete reset of the phone to factory settings, starting with a more gentle option, which is to reset the sensors only by calibrating them:

1. Open the Settings. → The phone.
2. Tap the MIUI version several times until you become a developer!
3. Return to the main Settings menu and open Additional Settings → For developers.
4. Scroll down and find Sensor Calibration Reset (or Sensor Setting Reset).
5. Confirm the action and restart the phone.

If this doesn’t help, do a full reset (with or without data saving):

1. Go to Settings → About the phone → Reset settings.
2. Choose Reset all settings (or Delete all data if you are ready to lose files).
3. Confirm the action and wait for the process to be completed.

⚠️ Warning: Full reset will remove all installed apps, photos and settings. Pre-backup important data via Settings → System and device → Backup.

Alternative ways to lock the screen during a call

If the proximity sensor is not working or it is not in your model, you can use alternative methods of locking the screen.

1. Power button locking

The easiest way to do this is to manually lock the screen with a power button while you're talking, and the problem is that you have to do this every time, but it works 100 percent.

2. Applications for forced blocking

Google Play has utilities that emulate the approach sensor or lock the screen on a timer.

• 📱 Proximity Sensor Fixer – Corrects sensor errors.
• 🔒 Call Screen Off – automatically locks the screen when you call.
• ⏱️ Screen Off and Lock – lets you create lock rules.

Install one of the applications, give it permission to access calls, and check it. Note that some utilities require Special Permissions in the MIUI settings.

3. Use of gestures

MIUI has a Gesture feature that allows you to swipe the screen, and it activates this way:

1. Settings → Lock screen → Gestures.
2. Turn on the swipe option down to lock.
3. During the call, swipe your finger from top to bottom across the screen to block it.

What to do if nothing helps

If none of these methods worked, the problem could be hardware.

1. Clean the proximity sensor. Gently wipe the area around the front chamber with an alcohol napkin, sometimes dust or fat interfere with proper operation.
2. Take off the protective film or the case. The tight accessories can block the sensor signal.
3. Update your firmware. Go to Settings → About Phone → Update your system and install the latest version of MIUI.
4. If the sensor is physically damaged, it will have to be replaced. In Xiaomi, it takes 1-2 days and is inexpensive (from 500 to 1500 rubles depending on the region).

⚠️ Please note: Do not try to disassemble Redmi by yourself. 9C This can cause the warranty to be lost or other components to be damaged, and the proximity sensor to the motherboard requires special equipment.

Important: On some versions of Redmi 9C (especially those with firmware for the global market), the lock screen function can be disabled at the system level, in which case only flashing to the official version of MIUI for your region will help.

FAQ: Frequent questions about screen locking on Redmi 9C