Calibration of the proximity sensor on Xiaomi Redmi 9 with NFC: fix screen errors during calls

Why is the proximity sensor on Redmi 9 with NFC not working properly?

The proximity sensor in Xiaomi Redmi 9 with NFC is responsible for automatically turning off the screen during phone calls when you bring the device to your ear. If it starts to fail, the screen either does not go out at all (which leads to accidental pressing), or turns off at inappropriate moments, interfering with the control of the smartphone, the causes of this malfunction can be both software and hardware.

Most often, the problem lies in the failure of the sensor calibration after updating the MIUI, mechanical damage (for example, after a phone drop), or contamination of the area around the sensor. Less often, the fault is incorrect firmware or conflict with installed applications. Before you carry the phone to the service center, you should try to recalibrate the sensor manually — it takes no more than 10 minutes and 80% of the time solves the problem.

In this article, we will discuss the unique calibration method for the Redmi 9 with NFC, which does not require root rights and works on all versions of MIUI (including MIUI 12/13/14), and learn how to check the performance of the sensor and what to do if the calibration did not help.

Signs of malfunction of the proximity sensor

Before you start calibrating, make sure the problem is really with the proximity sensor, and here are the main symptoms of it not working properly:

• 📱 The screen does not go out when you bring the phone to your ear during a call (the risk of accidental pressing).
• 🔄 The screen spontaneously turns off at inappropriate times (e.g., when reading messages).
• 🔦 The keylight or notification indicator flashes chaoticly.
• 📞 Calls are interrupted or switched to hands-free mode without your involvement.
• 🔧 In the phone settings, the sensor is displayed as "inactive" or shows incorrect values.

If at least one of these features is on a regular basis, it's likely that the sensor needs calibration, but there are exceptions: for example, a film or a case with metal elements can block the sensor signal. Before setting up, remove all the accessories and repeat the check.

Calibration Preparation: What to Do in Advance

Calibrating the proximity sensor on the Redmi 9 with NFC is a simple process, but it requires preparation.

1. Check the sensor's cleanliness. The sensor is at the top of the screen (near the speaker).Wash it with a soft napkin dipped in alcohol to remove dust and fat.
2. Make sure there is no physical damage.Cracks on the screen or dents in the sensor area may interfere with calibration.
3. Charge your phone at least 50%, interrupting the process due to battery drain can make the problem worse.
4. Back up your data. Although calibration doesn't affect user files, it's better to be safe.

It is also recommended to disable all applications that work in the background, especially those that use sensors (for example, fitness trackers or call programs), this will help to avoid conflicts during the procedure.

⚠️ Warning: If your Redmi 9 with NFC is warranty, self-calibration through the engineering menu can be considered an interference with the software.

Clean the sensor area from dust and dirt|Check the integrity of the screen and body|Charge your phone to 50% or more|Make a backup copy of important data|Disable background applications-->

Calibration of the proximity sensor on Redmi 9 with NFC

There are three main methods of calibrating the proximity sensor on the Xiaomi Redmi 9 with NFC:

1. Through the engineering menu (the most reliable way, works without root).
2. Using applications (such as Sensor Calibration or Proximity Sensor Reset).
3. Resetting to factory settings (last resort if other methods didn’t help).

We recommend starting with the engineering menu, as it gives direct access to sensor settings, which does not require third-party software installation and works on all versions of MIUI.

Method 1: Calibration through the engineering menu

To get into the engineering menu, follow the following steps:

1. Open the phone app and enter the combination: ##6484###
2. The MTK Engineer Mode menu will appear on the screen (if the combination doesn't work, try ##4636##).
3. Go to Hardware Testing → Sensor → Proximity Sensor.
4. Press Calibration and follow the instructions on the screen (usually you need to bring and withdraw your hand from the sensor several times).
5. Once completed, restart the phone.

If there is no calibration option in the engineering menu, try an alternative path:

• Enter the combination ##36446337## (for some versions of MIUI).
• Select the Proximity Sensor Test and perform the test by following the values on the screen.

⚠️ Warning: Some firmware may have the engineering menu blocked, in which case use the third-party application method or reset settings.

Method 2: Calibration with applications

If the engineering menu is not available, install one of the following apps from Google Play:

• 📱 Sensor Calibration – automatically detects and resets sensors.
• 🔧 Proximity Sensor Reset is a specialized tool for proximity sensors.
• 📊 CPU-Z – allows you to check the current sensor values (the Sensors tab).

Instructions for Proximity Sensor Reset:

1. Install and open the application.
2. Press Start Calibration.
3. Put your hand in the sensor for 3-5 seconds, then take it away.
4. Repeat the action 2-3 times until the application shows a successful completion.

Method 3: Resetting settings to factory

If the sensor is still not working properly, the last option is a hard reset, which will delete all data from the phone, so make a backup beforehand.

How to reset your settings:

1. Go to Settings → About the phone → Reset settings.
2. Select Delete all data.
3. Confirm the action and wait for the reboot.

After resetting, the sensor must return the factory calibration settings, if the problem remains, it is likely to be a hardware malfunction (for example, a sensor plume is damaged).

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Calibration through the engineering menu is the most reliable way, but if it didn’t work, try third-party apps or reset settings.

Checking of the proximity sensor after calibration

After calibration, you need to make sure that the sensor is working correctly.

1. Call another phone and check if the screen goes out when you bring the Redmi 9 with NFC to your ear.
2. Check through the Engineering Menu: Return to the Proximity Sensor Test and see how the values change when your hand approaches.
3. Use Apps: Install Sensor Test from Google Play and test all sensors.

Normal values of the proximity sensor:

If after calibration, the values remain in the range of 0.0-1.0 even when the phone is lying on the table, the sensor is still defective.

• 🔄 Recalibrate after 1-2 hours (sometimes it takes time to stabilize).
• 📱 Check your phone for viruses (they can block sensors).
• 🛠️ Contact the service center (possible hardware breakdown).

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If the sensor is only unstable in certain applications (such as WhatsApp or Telegram), try clearing the cache of these programs or reinstall them.

What if calibration doesn’t help?

If, after all the manipulations, the proximity sensor on the Xiaomi Redmi 9 with NFC still fails, the problem may be deeper.

1. Programmatic conflicts

Some applications (especially those that use sensors for gestures or automation) can interfere with the sensor.

• 📵 Temporarily disable all applications with administrator rights.
• 🔄 Reboot your phone in Safe Mode (hold the power button) → Restarting in Safe Mode).
• 🗑️ Remove newly installed programs.

Hardware malfunctions

If the sensor does not respond at all or shows deliberately false values (for example, 999), the following breakdowns are possible:

• 🔌 Damage to the plume connecting the sensor to the motherboard.
• 💧 Moisture entering the sensor area (even if the phone did not sink, condensation could damage the contacts).
• 🔨 Mechanical damage to the sensor (e.g. after a fall).

In these cases, self-repair is not recommended - it is better to contact the service center.The cost of replacing the proximity sensor with Redmi 9 with NFC usually does not exceed 1000-1500 rubles.

3. Firmware problems

Sometimes sensor failures are due to firmware errors.

• 🔄 Update. MIUI Up to the latest version (Settings) → The phone. → Updating the system).
• 📥 Install custom recovery (e.g., TWRP) and run through the clean version MIUI.
• 🔧 Return to a previous firmware version if the crashes started after the update.

⚠️ Warning: Flashing your phone without experience can lead to a "brick" (completely inoperable device). If you're unsure of your skills, trust it to the professionals.

Frequent calibration errors and how to avoid them

Many users make mistakes that cause even more sensor failures, and the most common ones are:

It is also not recommended:

• 🔨 Disassemble a phone without experience (risk of damage to plumes).
• 📲 Install unofficial firmware without backup.
• 🔧 Use calibration programs from unknown developers.

FAQ: Answers to Frequent Questions