The proximity sensor in Xiaomi smartphones is a small but critical element that is responsible for turning off the screen when you hold your phone to your ear. On the Redmi 9T (codenamed lime), this sensor often causes the sensor to malfunction or spontaneously turn off the display. If your device stopped responding to an approach, does not turn off the screen when you call or, conversely, goes out for no reason, the problem is likely to lie in this module.
Finding the proximity sensor on the Redmi 9T is not as easy as it seems: it is hidden under the top of the display and looks no different from other sensors (for example, lighting). In this article, we will discuss the exact location of the module, how to diagnose it without disassembling the phone, as well as typical faults associated with the sensor, you will learn how to check its performance using hidden MIUI menus and third-party applications, and what to do if the sensor is out of order.
Where is the proximity sensor on Xiaomi Redmi 9T: the exact location
On the Redmi 9T, the proximity sensor is integrated into the top sensor module, which also includes the light sensor and the front camera. Physically, it is a miniature infrared sensor hidden under a black strip (called a "monobra") above the display. Unlike some flagship Xiaomi models, where the sensor is made separately, in the Redmi 9T it is combined with the rest of the electronics in a single unit.
If you look at the phone as it is assembled, the proximity sensor is to the left of the front camera (if you hold the device with the screen to yourself), it cannot be seen with the naked eye, only through the magnifier or after disassembling the device, and inside the case, the module is soldered to the motherboard and connected to it through a flexible plume, which is also responsible for the operation of the display.
- 📍 External location: under a black strip above the screen, to the left of the camera.
- 🔧 Internal location: on the back of the display module, soldered to the board.
- 🔍 How to identify: when disassembling, marking is sought PROXIMITY or PS board-board.
It's important to understand that the approach sensor on the Redmi 9T works on the principle of infrared radiation: it emits an invisible beam and analyzes the reflected signal. If an obstacle appears in the path of the beam (for example, your hand or ear), the sensor sends a command to turn off the screen, which is why you need to check its performance in complete darkness, this prevents the influence of extraneous light.
How to check the proximity sensor without disassembling the phone
Before you disassemble the Redmi 9T, try to diagnose the sensor software. There are several ways to test that do not require special tools:
- Testing through the MIUI engineering menu. Enter the phone code ##6484##, then select Proximity Sensor. In the window that opens, you will see the current sensor reading: 0 means there are no obstacles, 1 - the sensor worked (approximation detected). Try to cover the top of the phone with your hand - the number should change.
- Use diagnostic apps. Install Phone Doctor Plus or CPU-Z from Google Play. In the Sensors section, search Proximity and check for your hand's response. If the readings don't change, the sensor is defective.
- Manual check during the call. Call another phone and hold the Redmi 9T to your ear. The screen should go out in 1-2 seconds. If it stays on or goes out with a delay of more than 3 seconds, the problem is confirmed.
Make sure there is no protective film or glass on the screen that blocks the IR ray
Test the sensor in complete darkness (exclude light exposure)
Try to clean the top frame of the screen from dust and dirt
Check the sensor response in the engineering menu and third-party applications-->
If the sensor does not respond to any of the actions, the reasons may be as follows:
- 🛠️ Mechanical damage: crack on the display module or detachment of the plume.
- 💧 Moisture: oxidation of contacts after getting wet.
- 🔌 Software failure: error in firmware or drivers MIUI.
- 🔋 Failure of the board: failure of the chip responsible for signal processing.
💡
If the sensor is too sensitive (the screen goes out at the slightest hand movement), try calibrating it through the engineering menu. To do this, type the code ##6484##, select Proximity Sensor Calibration and follow the instructions on the screen.
Typical malfunctions of the proximity sensor on the Redmi 9T
On the Redmi 9T model, the following problems with the proximity sensor are most common:
| Symptoms. | Probable cause | Elimination |
|---|---|---|
| The screen does not go out during the call. | Sensor contamination, plume damage, software failure | Cleaning, flashing, replacement of the display module |
| The screen goes out arbitrarily (without a call) | False positives due to dust or sensor damage | Calibration, sensor replacement |
| The sensor only works at a certain angle. | Separation of the plume or mechanical displacement of the module | Disassembly and fixation of the plume |
| Sensor readings are “hung” (always 0 or 1) | Failure of the chip or circuit break | Diagnostic board, replacement of sensor |
One of the most common causes of malfunction is the ingress of dirt or fat onto the sensor surface, which over time leads to the dispersion of the infrared beam and false positives. The solution is simple: gently wipe the top of the screen with a cotton swab dipped in alcohol. Don't use abrasive materials - they can scratch the coating!
⚠️ Warning: If the sensor still doesn't work after cleaning, don't try to disassemble the phone without experience. 9T The display module is connected to the board with a fragile plume, which is easily damaged if you unscrupulously dismantle.
How to Disassemble Redmi 9T to Access Approximation Sensor
If the software diagnostics didn't work, you'll have to disassemble the phone. The Redmi 9T is modular, but access to the proximity sensor requires you to completely dismantle the display module.
- 🔧 Plastic blades for disassembly.
- 🔥 Hair dryer or thermo-air station (for softening glue).
- 🧲 Magnetic screwdriver. T3 and T5.
- 📦 Screen-take-down suction cups.
Step-by-step:
- Turn off the phone and remove it. SIM-memory-card.
- Heat the screen edge dryer (~60°C) for 2-3 minutes to soften the glue.
- Put a plastic blade on the display, starting at the bottom edge, and be careful, there are plumes underneath the screen.
- Unscrew 4 screws that fix the metal plate over the battery.
- Disconnect the display plume and gently lift the module, and the proximity sensor will be located on the back side, next to the front camera.
After disassembly, inspect the plume for damage and check the contacts of the sensor with a multimeter (in vertebrae mode). If the resistance between the terminals tends to infinity, the sensor is defective and needs to be replaced.
What if the sensor doesn’t work after the disassembly?
Replacement of the proximity sensor: cost and nuances
The cost of replacing the proximity sensor with the Redmi 9T varies depending on the region and service center:
- 💰 Self-substitution: the new sensor will cost 300-800 rubles (depending on the supplier), but you will need to buy the entire display module, since the sensor is not sold separately.
- 🏠 Service center: the cost of work will be 1,500-3,000 rubles (including diagnostics). In official centers, Xiaomi may require the replacement of the entire display module, which will cost 4,000-6,000 rubles.
When choosing a service, pay attention to the following nuances:
- 🔍 Guarantee: official centers give a guarantee of 6-12 months, "handicraft" workshops - 1-3 months.
- 🛠️ Original parts: check whether the service uses original modules or Chinese analogues.
- ⚡ Repair time: on average, the replacement takes 1-2 days, but during peak periods (for example, before the New Year) it can take a week.
⚠️ Attention: If you decide to replace the sensor yourself, be prepared for the fact that after disassembly, the leakage of the body may break, this will lead to dust falling under the screen and deterioration of the sensor.
Software Ways to Solve Sensor Problems
It's not always hardware that causes the proximity sensor to malfunction. In 30 percent of cases, the software is the problem.
- Resetting to factory settings. Go to Settings → About Phone → Reset. This method will help if the failure is caused by an application conflict or an error in the cache of the system.
- Firmware update: Outdated versions of MIUI may contain bugs that affect sensor performance. Check for updates in Settings → System Update.
- Disable smart functions. Some MIUI features, such as wake up lifts or gestures, may conflict with the sensor. Turn them off in Settings → Screen → Additional.
- Custom core installation: For advanced users, some custom firmware (such as Pixel Experience or LineageOS) are better optimized for sensors, but this requires unlocking the bootloader and may be insecure.
If the problem occurs after you install a new app, try removing it and restarting your phone, and conflicts often arise with programs that use screen overlays (such as Blue Light Filter or Game Boosters).
💡
Before any firmware manipulation, check to see if the antivirus is blocking access to system files. Some applications (such as Avast or 360 Security) may prevent the MIUI from being updated.