Where is the proximity sensor in Xiaomi Mi 9 Lite: location, functions and diagnostics

Xiaomi Mi 9 Lite is a popular mid-range smartphone launched in 2019 that still remains relevant today due to its balanced performance and robust hardware platform. One of the key elements to ensure the user’s comfort is the proximity sensor, which is a small but important component responsible for automatically turning off the screen during phone calls, preventing accidental pressing and saving battery power.

Many users experience problems when the sensor stops working correctly: the screen does not go out when you hold the phone to your ear or, conversely, it turns off for no reason, often due to pollution, damage or improper settings. In this article, we will discuss in detail where the proximity sensor in the Mi 9 Lite is located, how it works, and provide practical tips for diagnosis and troubleshooting.

Physical location of the proximity sensor in the Mi 9 Lite

In the Xiaomi Mi 9 Lite, the proximity sensor is integrated into the top of the screen, next to the front camera and speaker, specifically to the right of the speaker, under the glass panel of the display, and visually it cannot be distinguished with the naked eye, since it is hidden under a black masking mesh (called a “curtain”), which also covers the front camera and the illumination sensor.

If you look at the front panel of the smartphone, the proximity sensor is located in the following order (left to right):

• 📞 Talking speaker (grid with small holes)
• 📷 Front camera (20 MPP, f/2.0)
• 🔦 Sensor of approach and illumination (under a black strip)
• 💡 LED indicator (if present in the modification)

Importantly, the Mi 9 Lite uses an infrared proximity sensor that relies on the reflected signal, and it emits an invisible infrared ray and analyzes its reflection from objects near the screen, and if the sensor is contaminated or closed with film/glass, its operation may be disrupted.

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To pinpoint the location of the sensor, turn on the engineering menu on the phone (code ##6484##) and select Proximity Sensor. Covering the upper right side of the screen, you will see the change in values in real time.

How the proximity sensor is arranged: the principle of operation

The Mi 9 Lite proximity sensor consists of two main elements:

1. Infrared emitter (IR LED) emits a light signal invisible to the human eye.
2. Photodiode (receiver) - captures the signal reflected from objects and converts it into an electrical impulse.

When you hold your phone to your ear while you're talking, the IR beam bounces off the surface and back to the photodiode. The microcontroller analyzes the intensity of the reflected signal and, if it exceeds the threshold, sends a command to turn off the screen. The response distance is usually 2-5 cm, but can vary depending on the firmware settings.

In the Mi 9 Lite, the proximity sensor is paired with the light sensor in the same module, but they operate independently of each other, which means that if the proximity sensor stops functioning, the light sensor can continue to adjust the brightness of the screen correctly, and vice versa.

Signs of malfunction of the proximity sensor

If the proximity sensor in your Mi 9 Lite has started to malfunction, you may see the following symptoms:

• 📵 The screen does not go out when you bring the phone to your ear during a ringing.
• 🔄 The screen is spontaneously turned on/off for no reason.
• 🕳️ Touch buttons are highlighted during the conversation (if the function "Disable button lighting" is disabled").
• 🔋 Fast battery discharge (if the sensor is constantly active due to a failure).
• 📱 Hanging or lags when using approximation functions (e.g., “Lifting to wake up").

Most often, problems arise due to:

• 🧴 Sensor contamination (dust, fat, film glue residues).
• 🛡️ Damage to glass or protective netting (cracks, chips).
• 🔧 Software failure (after updating or resetting settings).
• 🔌 Faulty plume (after disassembling the phone or falling).

⚠️ Warning: If the proximity sensor stops working after a phone drop or moisture hits, do not try to disassemble the device yourself, in this case, the probability of damage to the plume or chip is high, and professional diagnosis is required.

How to check the operability of the sensor of approach

Before you start repairing or settings, you need to make sure that the problem is really related to the sensor.

Method 1: Testing through the Engineering Menu

The most reliable way to check is to use a hidden engineering menu.

1. Open the phone app.
2. Enter the combination: ##6484## (for MIUI 12 and later).
3. Select the option "Proximity Sensor".
4. Cover the top of the screen with your hand – the value should change from “5” (no obstacle) to “0” (there is an obstacle).

Method 2: Checking through applications

If the engineering menu is not available, you can install third-party utilities, for example:

• CPU-Z (Sensors section).
• Sensor Test (shows the status of all sensors)
• Phone Doctor Plus (testing hardware components)

Method 3: Visual examination

Take a close look at the top of the screen for:

• 🔍 Cracks or chips on the glass above the sensor.
• 🧼 Pollution (dust, fatty spots).
• 📱 Films or glass covering the sensor (especially if it is metallized).

What to do if the proximity sensor is not working

If tests have confirmed a sensor malfunction, you can try the following ways to solve the problem:

1. Sensor cleaning

Often the cause is pollution.

• 🧷 Use a soft brush or cotton swab soaked in alcohol.
• 🚫 Don’t press hard – you can damage the glass.
• 🔄 After cleaning, restart the phone.

Calibration of the sensor

In some cases, software calibration helps:

1. Go to Settings → About Phone → MIUI version.
2. Click on MIUI Version 7-10 times to activate the developer mode.
3. Back to Settings → Additionally. → For developers.
4. Find the item "Calibration of the proximity sensor" and follow the instructions.

3. Resetting settings

If the problem occurs after the update, try resetting the settings:

• 🔄 Settings → System system → Resetting settings → Reset all settings.
• 📱 Do not reset to factory unless you have made a backup copy!

Replacement of the sensor

If the sensor is physically damaged, it needs to be replaced. In the Mi 9 Lite, it is soldered into the tail of the front camera, so you can't replace it separately, you have to change the entire module. Average repair cost in service centers: 1,500-2,500 ₽.

Frequent questions and user errors

When working with the proximity sensor, users often make mistakes that can exacerbate the problem, and consider the most common ones:

Mistake 1: Using metallized glass

Many of the security glasses have a metal spray that blocks the infrared signal, so if the sensor stopped working after the new glass was labeled, try:

• 🔍 Make sure there is a cutout in the sensor area.
• 📱 Replace glass with a model without metallization.

Error 2: Disabling the sensor in the settings

Some firmware has the option of turning off the proximity sensor.

• 📞 Settings → Calls. → Proximation sensor (to be switched on).
• 🔧 In the engineering menu (#6484##) PS Calibration should be active.

Mistake 3: Wrong firmware

If you have installed custom firmware (like LineageOS or Pixel Experience), the sensor may not work properly due to the lack of drivers.

• 🔄 Back to the official. MIUI.
• 📥 Find firmware with support for all sensors for your model.

⚠️ Note: If you notice that the proximity sensor is triggered too early (for example, when the phone is tilted), this may be due to increased sensitivity. In the engineering menu (#6484###), you can reduce the threshold value of the parameter. PS Threshold (optimal value: 3-4).

FAQ: Answers to popular questions

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If the proximity sensor in the Xiaomi Mi 9 Lite has stopped working, 80% of the time the problem is solved by cleaning, calibrating or resetting the settings. Physical replacement is required only if the plume or module is mechanically damaged.