Where is the proximity sensor in Xiaomi Mi 9T: location, inspection and repair

Introduction: why you need a sensor approach in a smartphone

The proximity sensor is one of those small but critical components of modern smartphones that users only remember when it stops working. In the Xiaomi Mi 9T (also known as the Redmi K20 in some regions), this sensor is responsible for automatically turning off the screen during a phone call when you hold the device to your ear. Without it, it would be extremely inconvenient to call: the screen would continue to respond to accidental touches with the cheek or ear, causing malfunctions in the call.

Many Mi 9T owners have problems when the sensor starts to work incorrectly — the screen does not go out when you call or, conversely, it turns off for no reason. Most often this is due to contamination of the sensor, damage to the plume or a software failure. But before you try to fix or calibrate the sensor, you need to know exactly where it is located and how it works. In this article, we will understand the location of the sensor on the Xiaomi Mi 9T, its technical characteristics and diagnostic methods.

Note that the Mi 9T uses an infrared proximity sensor that pairs with a light sensor (often confused for being close), which is important to consider when inspecting or repairing – damage to one can affect the operation of the other.

Where exactly is the proximity sensor in Xiaomi Mi 9T

In the Xiaomi Mi 9T, the proximity sensor is located at the top of the screen, to the right of the front camera. If you look at the front panel of the smartphone, you can find it in a small neckline (the so-called "fingers"), which also houses:

• 📸 Front camera (retractable, 20 MP)
• 💡 Light sensor (left of camera)
• 📱 Proximation sensor (right of camera, under glass)
• 🔊 Speaking speaker (over the cutout)

Visually, the proximity sensor looks like a tiny black spot about 2 mm in size, hidden under a protective glass. It is easy to confuse with a light sensor, but the latter usually has a translucent coating. To accurately identify the sensor, you can use a flashlight: when illuminated at an angle, the proximity sensor will look like a matte spot, while the light sensor is more transparent.

Important: In the Mi 9T, the proximity sensor is not mechanical, it's an infrared sensor that emits and picks up the reflected signal, so it can be disrupted by dirt, moisture, or damage to the protective glass.

Technical characteristics of the proximity sensor in the Mi 9T

The proximity sensor in Xiaomi Mi 9T is based on the STK3311 chip (or its analogue), which supports infrared detection of objects at a distance of up to 5-10 cm.

The Mi 9T’s sensor features integration with the light sensor in one module, which means that if one sensor is damaged, the entire unit may need to be replaced, and it is also calibrated in the factory and can only be changed softwarely (e.g., through an engineering menu).

Critical: In the Mi 9T, the proximity sensor doesn't have a separate connector on the motherboard, it's connected through a flexible display plume, which makes it difficult to replace it, as it requires a complete disassembly of the screen.

⚠️ Attention: If the sensor stops working after the smartphone falls, don't be in a hurry to change it. Often the problem lies in the disconnected display plume or damage to the contacts.

How to check the operation of the proximity sensor on Xiaomi Mi 9T

Before you take apart the phone, you should make sure that the sensor is the problem.

1. Test call: Call another phone and hold the Mi 9T to your ear. The screen should go out in 1-2 seconds. If it stays on, the sensor doesn't work.
2. Manual check: Enable dial mode and cover the top of the screen with your palm.The screen should go out (if the function is activated in the settings).
3. Engineering menu: Enter the code ##6484## → select Proximity Sensor → check the values when closing/opening the sensor.
4. Testing apps: Install a utility like Phone Doctor Plus or Sensor Test from Google Play.

If the sensor does not respond to any of the tests, the problem may be:

• 🧹 Contamination of glass above the sensor (dust, fat, moisture).
• 🔌 Damage to the display plume or contacts.
• 🤖 Firmware failure (solved by resetting or flashing).
• 🔧 Mechanical breakdown of the sensor (replacement required).

Check the sensor through the engineering menu

Clean the glass over the alcohol sensor

Make sure the problem is not with the cover or film.

Test resetting to factory-->

Cleaning and calibration of the proximity sensor

In 80% of cases, the sensor malfunction is due to contamination. To clean the sensor on the Xiaomi Mi 9T:

1. Turn off your smartphone.
2. Take a cotton swab dipped in isopropyl alcohol (at least 70%).
3. Gently wipe the area above the sensor (don’t press hard!).
4. Let the alcohol evaporate (2-3 minutes) and turn on the phone.

If cleaning doesn’t help, try recalibrating the sensor:

1. Enter the code ##6484## in the phone number.
2. Select Proximity Sensor.
3. Press Calibrate (if the option is available).
4. Follow the instructions on the screen (usually you need to close and open the sensor several times).

⚠️ Warning: Do not use acetone, water or aggressive solvents to clean the sensor, which can damage the protective coating of the glass and the sensor itself.

If the sensor is unstable after calibration (for example, the screen goes out with a delay), try to turn off the Smart Screen function in the settings (Settings → Display → Smart Screen).

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If the sensor doesn’t work after cleaning, try removing the protective film or cover – they can block the infrared signal.

Replacement of the proximity sensor: step-by-step instructions

If the sensor is completely out of order, it will have to be replaced. In Xiaomi Mi 9T, it is a complicated procedure, because it requires disassembling the screen. Without experience in repairing smartphones, it is better to contact the service center - an error can damage the plume or display.

For self-replacement will need:

• 🔧 Set of screwdrivers (cross, flat, pentalobe).
• 🧲 Screen suction cup.
• 🔥 Hair dryer or glue heating station.
• 📱 New proximity sensor (module with plume).
• 🧴 Clay. B-7000 or similar.

Step-by-step process:

1. Turn off the phone and remove it. SIM-map.
2. Heat the screen edge with a hair dryer (~60°C) to soften the glue.
3. Carefully tuck the screen with a suction cup and disconnect it from the body.
4. Unscrew the screws that fix the metal plate over the display plume.
5. Disconnect the display plume and carefully remove it.
6. Find the proximity sensor (it is glued to the inside of the glass) and replace it with a new one.
7. Collect the phone in reverse order using a new glue to lock the screen.

The cost of replacing the sensor in the service center is approximately 1,500–3,000 ₽ (Self-replacement is cheaper (~500–1 000 ₽ Partially, but the risk of damage to the phone is high.

Frequent proximity sensor problems and their solutions

Here are the most common failures and ways to fix them:

If the sensor starts to glittle after the firmware update, try to roll back to the previous version of MIUI.

1. Download the archive with the right firmware from the Xiaomi Firmware Updater website.
2. Go to Settings → About the phone → System update.
3. Click on the three dots in the upper right corner and select Select the firmware file.
4. Please enter the downloaded archive and wait for the process to be completed.

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Before any manipulation of the sensor, check whether the protective film or the cover is blocking its operation, and often the problem is solved by removing them.

FAQ: answers to frequent questions about the proximity sensor in the Mi 9T