Approximation Sensor on Xiaomi Redmi 9T: how to turn on, configure and check the health

The proximity sensor in Xiaomi Redmi 9T smartphones is a small but critical component that is responsible for automatically turning off the screen during phone calls. When you bring the device to your ear, the sensor registers the obstacle and extinguishes the display, preventing accidental pressing and saving battery power. However, many users face the problem: the screen does not turn off when talking, or the sensor does not respond at all to approach, most often due to software failures or improper settings, rather than hardware failure.

In this article, we will learn how to turn on the proximity sensor on the Redmi 9T, where to find the appropriate options in the menu, and what to do if the sensor stopped working after the MIUI update. You will also learn how to manually test the sensor using engineering menus and specialized applications, and why sometimes the problem lies in the protective glass or case, all instructions are adapted to the current versions of the firmware and tested in practice.

What is a proximity sensor and why you need it in the Redmi 9T

The proximity sensor is an infrared sensor located at the top of the Xiaomi Redmi 9T screen (usually next to the front camera) and its main function is to detect when you bring the phone to your ear during a call.

• 📱 Turns off the screen – to avoid accidental tapping of the cheek or ear.
• 🔋 Saves battery life – the display consumes up to 30% of energy when used actively.
• 🎧 Activates the speaker – switches the sound from the external speaker to the upper (conversational).
• 🔒 Blocks touch gestures – prevents hands-free or other functions from turning on.

The Redmi 9T uses an infrared sensor (as opposed to ultrasonic sensors in some flagships) that emits invisible light and analyzes the reflected signal. Operating range is up to 5 cm, which is enough for comfortable use. If the sensor is faulty or disabled, the screen will remain on while the call is being made and the touch buttons will remain active, resulting in:

• ❌ Accidental click on "Out" or "Loud communication".
• ❌ Quick battery discharge.
• ❌ Discomfort when talking (light screen distracts).

It's important to understand that the proximity sensor is not the same as the light sensor (which regulates the brightness of the screen), these two sensors are often side by side, but they perform different functions. On the Redmi 9T, they are combined into one module, but controlled separately.

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

On the Xiaomi Redmi 9T, the proximity sensor is located at the top of the front panel, to the right of the front camera, and can be visually identified by a small round or oval hole under the glass (sometimes hidden under the black grid).

• 📍 To the left of the speaker – if you look at the screen in a vertical position.
• 📍 Under the protective glass – often covered with a thin layer of film, which can interfere with work.
• 📍 Near the light sensor, these two sensors are usually combined into a single module.

To accurately identify the sensor, you can use a flashlight: in bright light, the infrared sensor can be slightly visible (although this depends on the model of the protective glass). On some Redmi 9T, the sensor is hidden under an opaque coating, in which case it can only be found from documentation or by disassembling the phone.

If you use a high-sided case or a thick protective glass, the sensor may not work properly, for example, a glass with darkened edges (like some Spigen or Ringke models) blocks the infrared signal, in which case it will help:

• 🔧 Replacement of glass with a model with a cutout under the sensor.
• 🔧 Use of a cover without top-side.
• 🔧 Calibration of the sensor through the engineering menu (more on this below).

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If you’ve recently glued a new protective glass and the sensor has stopped working, try gently wipe the area above the sensor with an alcohol wipe – sometimes glue or dust interferes with the signal.

How to turn on the proximity sensor on Redmi 9T through settings

In most cases, the proximity sensor on Xiaomi Redmi 9T is activated by default, but sometimes it can be disabled due to a failure or after resetting.

1. Open the Settings app (the gear icon on the home screen).
2. Go to the System and Device section → Additional settings.
3. Select the Special Opportunities item.
4. Scroll down and find the option of Approach Sensor (or Automatic Screen Disconnection in some versions of MIUI).
5. Make sure the switch is in the on position.

If your version of MIUI doesn’t have a separate point for the proximity sensor, try an alternative path:

1. Open Settings → Applications → Application Management.
2. Click on the three dots in the top right corner and select Show All Apps.
3. Find the Phone app and open its settings.
4. Check the Approach Sensor or Screen option during the call.

On some firmware (e.g. MIUI 12.5 or 13), the path may be different. If you do not find the right item, search the settings (the magnifier icon at the top) and enter the proximity sensor request.

Settings open. → System and device|Finding the section "Additional settings"|The option "approximation sensor" is checked"|Switch set to "On" position."-->

How to check the proximity sensor on the Redmi 9T

If you've turned on the sensor, but it's still not working, you need to check if it's working.

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

The most reliable method is to use a hidden engineering menu.

1. Open the Phone app.
2. Enter the combination: ##6484## (some firmware may not work – see alternatives below).
3. Select Proximity Sensor (Proximity Sensor).
4. Raise your hand to the top of the screen – the value should change from 5.00 cm to 0.00 cm.
5. Remove your hand – the value should return to 5.00 cm.

If the values do not change or if an error is displayed, the sensor is faulty or software locked. On some versions of MIUI, the engineering menu may be disabled - in this case, use alternative methods.

Method 2: Checking through the Sensor Test application

If the engineering menu is not available, install a third-party sensor testing app, such as Sensor Test or CPU-Z:

1. Download Sensor Test from Google Play.
2. Open the app and find the Proximity tab.
3. Put your hand in the sensor, and the status should change from Far (far) to Near (close).

If the app shows that the sensor is not responding, the problem may be:

• ⚙️ Software failure – requires a reboot or reset settings.
• 🛠️ Hardware malfunction – damage to the plume or the sensor itself.
• 📱 Protective glass/case – physical signal blocking.

Why the proximity sensor doesn't work on the Redmi 9T: the main reasons

If the sensor doesn't work during a call or doesn't respond to tests, the reasons can be both software and hardware.

One of the most common causes is a conflict with the MIUI shell, for example, after upgrading to MIUI 13, some users have experienced that the proximity sensor stopped working in the Phone app, but functioned normally on WhatsApp or Telegram, in which case:

• 🔄 Cleaning the cache of the phone application (Settings) → Annexes → Phone. → Warehouse → Clear the cache).
• 🔧 Reset application settings (ibid., Reset button).
• 📥 Install an alternative call (e.g. Google Phone).

Important: If the sensor doesn’t work in just one application (like Viber), the problem lies in the settings of that particular messenger, not the hardware. Check the permissions for the application in Settings → Applications → [App name] → Permissions.

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If the proximity sensor stopped working after a phone drop or moisture hit, there is a 90% chance that the module will need to be replaced. Self-repair is not recommended - the risk of damage to the display plume.

How to Calibrate the Approach Sensor on Redmi 9T

If the sensor is unstable (for example, the screen is turned off with a delay or does not turn back on), it can be calibrated.

Method 1: Through the Engineering Menu

1. Open the engineering menu (code ##6484##).
2. Select Proximity Sensor.
3. Press Calibrate.
4. Follow the instructions on the screen (usually hold and remove your hand several times).
5. Save the settings and restart the phone.

Method 2: Sensor Calibration App

If the engineering menu is not available, use third-party utilities:

1. Install Sensor Calibration.
2. Select Proximity Sensor.
3. Press Start Calibration and follow the instructions.

After calibration, check the sensor again, and if the problem persists, you may need to reset to the factory settings:

⚠️ Warning: Resetting to factory settings will remove all data from the phone, including photos, contacts and apps. pre-backup through Settings → The phone. → Backup.

1. Go to Settings → About the phone → Reset settings.
2. Select Reset all settings.
3. Confirm the action and wait for the reboot.

What to do if the proximity sensor is broken: repair or replacement

If all software methods have been tried, but the sensor still doesn't work, it's probably a hardware problem. In the Xiaomi Redmi 9T, the proximity sensor is soldered into a common module with a front-facing camera and light sensor, so replacing it requires disassembling the phone.

Signs of hardware malfunction:

• 🚨 The sensor does not respond to tests or calibration.
• 🚨 The engineering menu displays the Sensor error.
• 🚨 The light sensor also stopped working (they often break together).

Cost of repairs in service centers:

If you want to repair your phone yourself, consider:

⚠️ Note: When disassembling Redmi 9T It is easy to damage the plume of the display or battery. Without experience, it is better not to take risks - the cost of repair after a failed self-attempt can grow 2-3 times.

To replace the sensor will require:

• 🛠️ New sensor module (can be found on AliExpress or in service centers).
• 🔧 Set of screwdrivers (star) T3, T4).
• 🧲 Screen suction cup and mediator.
• 🔥 A dryer or a station for heating the glue (display glued).

You can find the Redmi 9T step-by-step disassembly instructions on YouTube (we recommend Xiaomi Repair or Fixez channels), but remember: self-repairing is not warranty if it is still valid.

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