Approximation Sensor in Xiaomi Redmi 9T: where is it, how to check and troubleshoot

The proximity sensor in Xiaomi Redmi 9T smartphones is a small but critical element that automatically shuts down the screen during a phone call. When you bring the device to your ear, the sensor registers the obstacle and extinguishes the backlight, preventing accidental pressing and saving battery power. However, many users face problems: the screen does not go out when calling, reacts with a delay or, conversely, it turns off for no reason, most often due to contamination, damage or improper calibration of the sensor.

In this article, we will detail where the proximity sensor in Redmi 9T is located, how to visually identify it, and provide step-by-step instructions for diagnosing and fixing typical malfunctions. You will learn whether you can clean the sensor yourself, which applications will help test it, and in which cases you will need to contact the service center.

Where is the proximity sensor on Xiaomi Redmi 9T: the exact location

In the Xiaomi Redmi 9T, the proximity sensor is integrated into the top of the screen, next to the front camera and speaker, and specifically, it is located to the left of the selfie camera, if you look at the screen in the standard position (the speaker at the top), visually, the sensor is a small circular hole with a diameter of about 2 mm, covered with a protective glass, on some devices it can only be seen at a certain angle or in bright light.

It's important to understand that the proximity sensor is not a single module, but part of a touch unit that also includes the light sensor. The Redmi 9T uses an infrared (IR) sensor that works on the principle of reflecting the signal: it emits an invisible beam and analyzes its return. If the beam reflects off an obstacle (for example, your ear), the smartphone knows that the screen needs to be turned off.

• 📍 Exact location: left of front camera, under protective glass.
• 🔍 How to find: Light a flashlight at an angle – the sensor will look like a small dark spot.
• ⚠️ Careful: Do not confuse with a light sensor (located to the right) or a microphone (below).

The image below shows the Redmi 9T upper panel with the proximity sensor designation (marked with a red circle).Note that on some devices the protective glass may be darkened, making it difficult to visually inspect.

How the proximity sensor works: the principle of operation and typical failures

The proximity sensor at Redmi 9T It's based on infrared radiation, and it's made up of two key elements: a emitter. IR-And the signal, and the receiver, which picks up the reflected signal, and when you hold the phone to your ear, the beam bounces off the surface and comes back, which is the command to turn off the screen:

1. The smartphone registers the start of the call.
2. The sensor is activated and starts emitting. IR-rays.
3. When an obstacle is detected (less than 5 cm), the screen goes out.
4. After removing the obstacle, the screen is turned on again.

Typical proximity sensor malfunctions in Redmi 9T fall into two categories: software (software failures, incorrect settings) and hardware (pollution, damage, wear and tear).

Interestingly, in some cases, proximity sensor problems may be related to a malfunction of the display module, for example, if the sensor stopped working after the screen was replaced, it is likely that the master damaged the plume or improperly connected the connectors, in which situations require re-disassembly of the device.

How to check the proximity sensor on Xiaomi Redmi 9T: 3 working methods

Before you start repairing or cleaning a sensor, you need to make sure that the problem is really there, and there are some reliable diagnostic methods that don't require special tools, and we recommend using them consistently, starting with the simplest.

Method 1: Testing through the Engineering Menu

The engineering menu (#4636##) allows you to test all sensors of the smartphone, including the proximity sensor.

1. Open the Phone app and enter the combination ##4636##.
2. Select Testing (or Testing)
3. Click on Proximity Sensor.
4. Raise your hand to the top of the screen – the value should change from 5.0 cm to 0.0 cm.

If the values do not change or an error is displayed, the sensor is faulty.

Method 2: Using Third-Party Applications

Apps like Phone Doctor Plus or Sensor Test (available on Google Play) provide more visual diagnostics, and they show a real-time graph of the sensor's response.

• Install and open the application.
• Select the Proximity Sensor section.
• Cover the sensor with your finger – the graph should drop sharply to zero.

If the graph doesn’t respond or shows chaotic jumps, it indicates a hardware fault.

Method 3: Manually check during a call

The easiest test is to call another phone and watch the screen behavior:

1. Dial the number and start the call.
2. Hold the phone to your ear, the screen should go out.
3. Put the phone away, the screen should turn on again.

If the screen doesn’t react or behaves unpredictably, move on to cleaning or calibration.

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If the sensor does not respond to any of the tests, the problem is likely hardware (damage to the sensor or plume).

Cleaning the proximity sensor: step-by-step instructions

Most often, the proximity sensor stops working because of pollution: dust, fat or moisture block the infrared signal. Cleaning is the first step to try before you go to the service. It is important to act carefully so that you do not damage the protective glass or the sensor itself.

You'll need:

• 🧴 Alcohol wipes (or cotton swab) + isopropyl alcohol 70%).
• 🔦 Bright flashlight or magnifying glass.
• 🧲 Soft brush (for example, for the camera lens).
• 📱 Plastic spatula (for careful removal of dirt).

Step-by-step cleaning process:

⚠️ Warning: Never use sharp objects (needles, toothpicks) to clean the sensor, which can damage its membrane. Also avoid getting liquid inside the case. If the sensor does not work after cleaning, likely it will need to be replaced.

If the contamination is severe (for example, dirt got under the protective glass), you may need to disassemble the phone, in this case it is better to contact the service center, since self-disassembly without experience can damage the plumes or display.

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To prevent contamination of the sensor, use a protective film with a cutout for the upper panel or a case that does not cover the proximity sensor.

Calibration of the proximity sensor: when and how to do it

Sometimes the proximity sensor doesn't work properly because of physical damage, but because of calibration failure, which can happen after updating the firmware, resetting the settings or installing custom software. Calibration helps the smartphone to correctly interpret the sensor signals.

For Xiaomi Redmi 9T, there are two ways to calibrate:

Method 1: Through the Engineering Menu

This method requires access to the engineering menu:

1. Enter the code ##4636## in the Phone app.
2. Go to Testing. → Proximity Sensor.
3. Press Calibrate (or Calibration).
4. Follow the instructions on the screen (usually hold and remove your hand several times).

Method 2: Proximity Sensor Reset

If the engineering menu is not available, install a specialized application:

1. Download Proximity Sensor Reset from Google Play.
2. Open the app and press Calibrate.
3. Put your hand in the sensor and wait for the process to be completed.
4. Reboot the phone.

⚠️ Attention: Incorrect calibration may worsen the sensor. If problems persist after the procedure, return the settings to factory settings (Settings) → System system → Resetting settings).

In Redmi 9T models with MIUI 12.5 firmware and later calibration through the engineering menu can be blocked, in which case only resetting or software updates will help.

What to do if the proximity sensor does not work: an algorithm of actions

If cleaning and calibration didn’t help, follow this algorithm to troubleshoot the problem:

1. Check for software updates. Go to Settings → About Phone → System Update and install the latest version of MIUI. Often sensor bugs are fixed in new builds.
2. Remove conflicting applications. Some programs (such as modified launchers or call apps) may block the sensor. Try to start the phone in Safe Mode (hold the power button → Safe Mode).
3. Reset the settings to factory. This will help if the problem is caused by a software failure. Be sure to back up the data (Settings → Additional → Backup).
4. Check the integrity of the plume, if the phone fell or disassembled, the plume connecting the sensor to the motherboard could be damaged, and it would require disassembly.
5. If all previous steps have failed, it is likely that the sensor or its components have failed and need to be replaced.

The cost of replacing the proximity sensor in Redmi 9T varies from 800 to 1500 rubles (depending on the region and service).In some cases, the masters offer to replace the entire display module, which will cost more (3000-5,000 rubles), but guarantees the performance of all sensors.

Frequent questions about the proximity sensor in Xiaomi Redmi 9T