Checking the proximity sensor on Xiaomi Redmi 9T: from diagnosis to repair

Introduction: Why the proximity sensor is important for the Redmi 9T

The proximity sensor in the Xiaomi Redmi 9T is a small but critical component that automatically shuts down the screen during phone calls. When you bring the device to your ear, the sensor picks up the obstacle and extinguishes the display, preventing accidental taps and saving battery power. However, over time, this module can fail: the screen stops responding to approach, stays on during a call or, conversely, goes out for no reason.

The proximity sensor problems on the Redmi 9T are often confused with software failures or display defects. For example, users complain of a constantly burning screen when calling, which leads to the pressing of buttons with the cheek or ear, or vice versa, spontaneously turning off the screen in the pocket. In 80% of cases, it is the sensor that is to blame, not the firmware or mechanical damage. But how to accurately determine the malfunction? In this article, we will discuss 5 reliable methods of verification, including hidden engineering menus, test calls and hardware diagnostics.

Before you run to the service center, try to diagnose the problem yourself. Most of the malfunctions of the proximity sensor on the Redmi 9T can be detected without special equipment, just follow our instructions.

Signs of malfunction of the proximity sensor

How do you know if your Redmi 9T's proximity sensor isn't working properly?

• 📱 The screen doesn't go out during a call, even when you hold the phone to your ear, resulting in random button presses, the microphone being turned off, or the call being completed.
• 🔄 The screen spontaneously turns on/off in a pocket or bag, as if the sensor were falsely triggered by obstacles.
• 🔍 Power consumption has increased markedly, with the sensor draining the battery faster than usual in a constant “active” mode.
• 📞 Problems with autorotating the screen (although this is more commonly associated with the gyroscope, but sometimes the symptoms overlap).
• 🛠️ Sensor error messages in the engineering menu (more on this in the next section).

It is important to distinguish sensor malfunction from other problems. For example, if the screen does not respond to touch at all (even outside the call), it is more likely to blame the touchscreen or the display plume. And if the screen goes out but the sound disappears when you talk, check the microphone or speaker. On the Redmi 9T, the proximity sensor is located next to the top speaker (near the front camera), and its contamination or damage can affect the operation of neighboring modules.

⚠️ Warning: If the proximity sensor starts to glittle after the phone falls or moisture hits, there is a high probability of mechanical damage, in which case self-diagnosis may not work, it requires disassembling the device.

Method 1: Check through the engineering menu (code ##6484##)

The most reliable way to test the proximity sensor on the Redmi 9T is to use a hidden engineering menu.

1. Open the Phone app.
2. Enter the combination: ##6484### (some firmware may require ##4636##, then go to the Hardware testing section).
3. In the menu that opens, select Proximity Sensor.
4. Cover the top of the screen (where the front camera is located) with your hand or an opaque object.

In working condition, you will see:

• 🟢 The value of "0" is when the sensor is not closed (no obstruction).
• 🔴 The value of "1" is when the sensor is closed (there is an obstacle).

If the values do not change or are displayed incorrectly (for example, always "0" or "1"), the sensor is defective. Also note the maximum and minimum values in the menu - if they are equal (for example, both "0"), this confirms the breakdown.

Close all applications

Make sure there is no protective film or glass on the screen.

Check that the top of the phone is clean (no dust, dirt)

Use an opaque object (hand, book, non-transparent case)

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On Redmi 9T with MIUI 12.5+ firmware, the engineering menu can be blocked. If the code doesn't work, try an alternative method through the CIT app (see Method 3).

Method 2: Test call (real-world test)

If the engineering menu is not available, check the proximity sensor in real-world conditions:

1. Call another phone (or ask a friend to call you).
2. Take the call and hold the Redmi 9T to your ear.
3. The screen should go out instantly (usually within 0.5-1 seconds).
4. Take the phone away from your ear, the screen should light up again.

Repeat the action 3-5 times. Pay attention to:

• 🔹 Reaction delay – if the screen goes out after 2-3 seconds, the sensor is slow (calibration may be required).
• 🔹 False positives – the screen goes out when the phone is lying on the table or you just hold it in your hand.
• 🔹 No response – the screen remains on regardless of the position of the phone.

For a more accurate test, use the hands-free mode:

1. During the call, turn on speaker.
2. Put your hand on the top of the phone (to the sensor).
3. The screen should remain on – if it goes out, the sensor will work falsely.

⚠️ Warning: On Redmi 9T with custom firmware installed (e.g. LineageOS), the logic of the sensor may differ, in which case the test call is better combined with the check through the engineering menu.

Method 3: Diagnostics through the CIT (Mi Test) application

Xiaomi provides an official iron testing app, CIT (Mi Test), which is pre-installed on most Redmi devices, but if it isn’t, download it from the Mi App Store or Google Play (called the Mi Test or Hardware Test).

Instructions:

1. Open CIT.
2. Go to the Proximity Sensor section (may be called the Approximation Sensor or Sensor Test).
3. Follow the instructions on the screen: the application will ask you to close and open the sensor in turn.

The annex will show:

If the CIT is making an error, but the engineering menu is showing the correct values, the problem may be in the software. Try updating the firmware or resetting to factory settings (see "What to do if the sensor does not work").

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If the CIT app is not on your Redmi 9T, try alternative tools from Google Play, such as Sensor Test or Phone Tester. These are less accurate, but will help confirm the malfunction.

Method 4: Checking through ADB (for advanced users)

If standard methods don't work, you can check the proximity sensor through the ADB (Android Debug Bridge), which requires a computer and basic command-line skills.

Instructions:

1. Turn on Developer Mode on Redmi 9T: go to Settings → About Phone → MIUI version and press 7 times in a row.
2. Return to Settings → Additional → For developers and enable USB debugging.
3. Connect your phone to your computer and open the Command Prompt (Windows) or Terminal (macOS/Linux).
4. Enter the command: adb shell dumpsys sensorservice Look for the line with proximity in the output.
5. For real-time monitoring, use: adb shell getevent -l Close/open the sensor and observe changes in the log.

In normal state, when you close the sensor, you will see an event with a value of 1, when you open it - 0. If the values do not change or are absent at all, the problem is hardware.

⚠️ Warning: Using ADB can cause a phone to malfunction if you give the wrong commands. Do not change the sensor settings through ADB without a clear understanding of the consequences.

Method 5: Calibration of the proximity sensor

Sometimes the proximity sensor on the Redmi 9T doesn't work properly because it's broken, but because it's got a wrong setting, and in this case, calibration will help, and you can do this in two ways:

Method 1: Through the Engineering Menu

1. Open the engineering menu (code ##6484##).
2. Select Proximity Sensor.
3. Press Calibrate and follow the instructions.

Method 2: Sensor Calibration App

Download a sensor calibration app from Google Play (such as Sensor Calibration or GPS & Sensors Toolbox). From the menu, find the proximity sensor calibration section and perform the procedure.

After calibration:

• 🔄 Reboot the phone.
• 📞 Check the sensor with a test call.
• 📊 If the problem persists, go back to the engineering menu and check the sensor values.

Calibration helps in 30-40% of cases when the sensor starts to glittle after updating the firmware or mechanical impact (for example, after changing the screen).

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Calibration of the proximity sensor resets its settings to factory. If after the procedure the sensor becomes worse, repeat the calibration or go back to the previous firmware (if the problem occurred after the update).

What to do if the proximity sensor is not working

If all tests have confirmed a malfunctioning proximity sensor on the Redmi 9T, you have several options:

If you want to clean the sensor yourself:

1. Turn off the phone.
2. Gently wipe the top of the screen (near the front camera) with a cotton swab soaked in isopropyl alcohol.
3. Do not use sharp objects or abrasive materials!
4. Let the phone dry for 10-15 minutes before turning on.

If the sensor is physically damaged, it will be cheaper to replace it than the entire display module. However, on the Redmi 9T, the sensor is often soldered into the screen plume, so services may suggest replacing the entire screen.

Temporary solution (if the sensor is not working and repair is delayed):

• 📵 Turn off the Screen function during the call in the settings (Settings → System Applications → Phone → Screen during the call).
• 🔕 Use a headset or speakerphone to avoid accidental tapping.

FAQ: Frequent questions about the proximity sensor on Xiaomi Redmi 9T