How to turn on the proximity sensor on Xiaomi Mi 9 Lite

Owners of Xiaomi Mi 9 Lite smartphones often face a situation where the screen does not go out during a phone conversation.This leads to accidental tapping of the cheek or ear, which can interrupt the call or trigger unnecessary functions. The proximity sensor is a tiny but critical element that should automatically turn off the display when you bring the device to your face.

In MIUI, the control of this sensor is not always obvious. Sometimes the function is software-enabled, and other times it requires manual calibration to work properly. Understanding the operation of the infrared sensor will help you avoid communication problems.

In this article, we will discuss in detail how to activate the sensor, make it precise, and what to do if the software methods do not help. On the Xiaomi Mi 9 Lite, the sensor is hidden under the display at the top of the screen, making it invisible, but requiring a clean surface for stable operation.

The principle of operation of the sensor in the MIUI shell

The technology for detecting objects in the vicinity of a smartphone is based on the emission of invisible light. The infrared emitter sends a signal that bounces off the obstacle and returns to the receiver. If the reflection is fixed, the Android system blocks the touchscreen and extinguishes the matrix.

The Xiaomi Mi 9 Lite features a hidden component layout, and the lack of a visible hole in the top frame means that the sensor is designed to work through the display glass, which imposes certain requirements on the integrity of the protective film and the cleanliness of the screen.

The MIUI shell takes over the sensor signal processing, so if the software algorithm gets false data, the screen can behave in an unpredictable way, for example, it can not light up when the phone is removed or, conversely, burn constantly.

⚠️ Attention: The use of thick protective glasses with an opaque perimeter frame often covers the area of operation of the hidden sensor, making it useless to turn on without replacing the accessory.

To work properly, the system needs to know the specific thresholds for the response, which is why after a glass change or failure, a calibration procedure is required, which we will discuss below.

Activation of the function in the standard menu

The first step to fixing the problem is to check the basic telephony settings, and in most cases, the sensor is already on, but the failure may have occurred after the system update, so you need to go to the Phone app and open the settings through a three-dot menu.

In the list that opens, look for Incoming Calls, and that's where the lock switch is located, make sure it's active, and if the slider is gray and not pressed, maybe access rights are limited by system permissions.

Sometimes, once activated, you need to reboot the device to apply the changes. Xiaomi Mi 9 Lite may take time to re-initialize the sensor drivers. Don't ignore this simple step, as it solves 80% of software conflicts.

• 📱 Open the phone application (green handset).
• ⚙️ Click on the three dots in the top right corner and select Settings.
• 🔍 Find the Incoming Calls section.
• ✅ Activate the switch The proximity sensor.

If the problem persists after switching on, move to a deeper diagnosis. The lack of response to the settings indicates the need to use an engineering menu.

Engineering menu and precise calibration

When standard methods fail, a hidden engineering interface comes to the rescue, a powerful tool for testing hardware components, and it uses special code to enter it, which runs on most Xiaomi devices.

Open the dialer and dial the combination ##6484##. Immediately after entering the last star, the CIT (Customer Integrated Test) menu will open.

In this section, you'll see the current sensor readings, so you can close the top of the screen with your palm, and it should change from 5.0 (or 0.0) to the opposite, and if there's no response, it may be physically defective or contaminated.

To calibrate, press the Calibration button at the bottom menu. Follow the instructions on the screen: you usually need to close, then open the sensor several times. Once successful, the Pass message will appear.

⚠️ Note: Do not calibrate while holding your phone in a case or under bright direct sunlight, as this will distort the reference light values.

After calibration, be sure to restart your smartphone. The MIUI system must count new sensitivity factors. If the CIT test shows Fail even after calibration, the problem is hardware-based.

Diagnostics through the Mi Test application

An alternative way to check is to use the built-in Mi Test application, which is often pre-installed in the Service or Tools folder, which is more user-friendly than the engineering menu.

Run the app and select the Approximation Sensor test, turn the screen green, and the system will ask you to close the top of the device, and if you pass the test, you confirm that the hardware is working, and you need to dig towards the software.

If the Mi Test app gives you an error, try clearing the cache of the Phone system application. Go to Settings → Apps → All Apps → Phone → Memory → Clear. This won’t delete contacts, but will reset your call settings.

Impact of protective accessories and cleaning

The Xiaomi Mi 9 Lite has a narrow frame, and any shift in the protective glass can block the area of the sensor, check if there are air bubbles or dust at the top of the screen.

Fat spots from your fingers can also scatter the infrared beam, making the phone think it's near your ear. Rub the screen regularly with a microfiber, paying special attention to the area above the speaker.

💡

If you use hardened glass with a black frame, try gently cutting or tearing the black strip over the speaker if it overlaps the invisible sensor.

Remove the case while you're diagnosing. Some tight silicone bumpers have high sidebars that mechanically obscure the sensor without even a bell, a common problem with third-party accessories.

• 🧼 Wipe the screen with an alcohol-containing solution.
• 👀 Inspect the sensor area in bright light for chips.
• 📱 Remove the protective glass to check without it.
• 🧤 Make sure the cover does not press on the upper end of the body.

If removing protection has helped, replace the accessory with a better one, labeled Compatible with Proximity Sensor. Cheap glass often has opaque adhesive in the sensor area.

Solving firmware problems and resetting

In rare cases, the MIUI operating system itself is the culprit. Errors in the code can block the driver from working. Check for updates in Settings → About the phone. Sometimes Xiaomi releases patches that fix the sensors.

If the update didn't work, you can try resetting everything to factory settings. Importantly, this will delete all your data, so back up. Once reset, the phone will go back out of the box and the software conflicts will be fixed.

For advanced users, it is possible to flash the device; installing a global version instead of a Chinese one (or vice versa) often solves problems with incorrect drivers, but it is a complex procedure that requires unlocking the bootloader.

⚠️ Warning: Before performing a full reset (Wipe Data), make sure you remember the password from your Mi and Google account, otherwise activation lock will make the phone unusable.

If even the clean firmware doesn't activate the sensor, it's likely that the problem is the physical failure of the plume or the module itself, and then only a visit to the service center will help.

Frequently Asked Questions (FAQ)

💡

If the software methods and calibration did not help, and the screen still does not go out – in 90% of cases, a replacement of the sensor module or plume in the service center is required.