You dial a number on Xiaomi Redmi 9, hold the phone to your ear, and the screen suddenly goes out. The call goes, the interlocutor hears you, but you can bring the display back to life only by taking the device or pressing the power button. Familiar situation? This problem is common among many owners of Redmi 9 (including modifications of Redmi 9A, 9C, 9T) and is associated with the operation of the proximity sensor, MIUI firmware or hardware malfunctions.
In 80 percent of cases, the proximity sensor is responsible for turning off the screen when the phone is held to the ear to avoid accidental tapping, but if the sensor is triggered too early, malfunctioning or its data is ignored by the system, the screen goes out even when you just dial. Other times, the problem lies in MIUI settings, application conflicts or even mechanical damage. Next, we will examine all possible causes, from the simplest to those that require the intervention of the service center.
1. The proximity sensor: how it works and why it fails
The proximity sensor in Redmi 9 is located next to the front camera, and it's an infrared sensor that emits invisible light and tracks its reflection: if the phone is close to the ear (or other object), the sensor sends a signal to the system to turn off the screen, normally only during a call, but if the sensor is contaminated, damaged or miscalibrated, it can also fire when dialing.
The main reasons for incorrect work:
- 🔦 Sensor contamination – dust, greasy traces or protective film block infrared signal.
- 🛠️ Mechanical damage - cracks on glass, impacts, moisture intrusion.
- 📱 Calibration failure - after update MIUI or resetting the sensor may work unstablely.
- 🔄 Conflict with the shell - in some versions MIUI 12/13 There are bugs with the processing of sensor signals.
To check the sensor, use the service code:
##6484##Once you enter, the Mi Test menu will open. Select Proximity Sensor and hold your hand to the top of the screen. If the sensor is working, a green tick or Near will appear on the screen. If there is no reaction or Far is displayed even when you close the sensor, the sensor is defective.
2. Checking MIUI settings: what could have gone wrong
Sometimes the problem is not hardware, but software settings. MIUI has a few parameters that can affect the approach sensor and the screen during calls:
- In your pocket mode (Settings → Screen → In your pocket) – if it’s on, the phone can lock the screen whenever you touch the sensor.
- Screen gestures (Settings → Screen → Lock screen gestures) – a conflict with the sensor can occur if gestures such as “Raise to wake up” are activated.
- Energy saving (Settings → Battery → Energy saving mode) – in aggressive modes, the system can forcibly turn off the screen.
It is also worth checking the settings of the phone application:
- Open the Phone app.
- Click on the three dots in the top right corner and select Settings.
- Check the Screen items during the call and the Approach Sensor (if any in your version of MIUI).
💡
If the phone does not have a “approximation sensor” option in your settings, try resetting the Phone app to the standard settings: Settings → Applications → Application Management → Phone → Storage → Settings Reset.
3. Software glitches: updates, cache and conflicts
If the proximity sensor is in good shape and the MIUI settings don't help, the problem could be software-related.
- 🔄 Older versions of the old version MIUI 11-12 There were bugs with the sensor signal processing.
- 🗑️ Filled cache – system cache files may conflict with sensors.
- 🤖 Third-party apps – some programs (especially optimizers or launchers) interfere with screen control.
How to fix software failures:
Clear the cache of the Phone application |Delete the system cache in Settings → Memory → Clean |Update MIUI to the latest version |Check conflicting applications in Settings → Apps → Permissions → Autorun-->
If the problem has occurred after the MIUI update, try to roll back to the previous version via Fastboot or Recovery. Instructions for Redmi 9 are available on the official Xiaomi forum (Mi Community → Redmi 9 → Firmware).
⚠️ Attention: Firmware rollback erases all data on the phone. Pre-backup through Settings → Additionally. → Backup and reset.
Mechanical damage: when iron is to blame
If software methods didn't help, the problem could be hardware. In Redmi 9, the proximity sensor and the screen backlight are linked to a flexible plume that wears out or gets damaged over time.
- 📱 The screen goes out even without calls (for example, when the phone is tilted).
- 🔦 The proximity sensor does not respond to the test code # #6484##.
- 💡 The screen lighting flickers or spontaneously changes the brightness.
Other possible causes:
| Malfunction | Signs. | Decision |
|---|---|---|
| Sensor plume damaged. | The screen goes out when you press the top of the phone lightly. | Replacement of the plume in the service center |
| Oxidation of contacts | The problem appears after getting moisture | Cleaning or soldering contacts |
| Display module malfunction | The screen is completely dimmed without any reaction to the buttons. | Screen replacement |
| Failure of the power controller | The phone spontaneously reboots. | Diagnosis of the motherboard |
If you suspect a mechanical malfunction, don’t try to disassemble the phone yourself – in Redmi. 9 The plumes are very fragile and easily damaged. Contact the Xiaomi Authorized Service Center (list available on the website). mi.com/ru/service).
Conflicts with SIM-map-and-net
Rarely, but sometimes the screen goes out because of problems with the screen. SIM-This is because when you dial a number, the phone accesses the communication module, and if there's a malfunction, the system may not be able to process the sensor signals properly.
How to check:
- Try calling someone else. SIM-Cards (if the phone supports two SIMs).
- Switch from 4G on 3G in network settings (Settings) → SIM-maps and mobile networks → Preferred type of network).
- Turn off VoLTE (Voice over LTE) in the same settings.
If the screen stops going off after the change SIM-maps or VoLTE shutdowns, the problem is the communication module:
- 🔄 Update of the module firmware (via MIUI service-centre).
- 📶 Resetting network settings (Settings) → System system → Resetting settings → Resetting network settings).
6. Alternative solutions: if nothing has worked
If all of the above methods have not worked, try these options:
How to turn off the proximity sensor completely (not recommended!)
Other ways:
- 🔧 Reset to factory settings - deletes all data, but often resolves software conflicts. → Additionally. → Backup and reset → Resetting settings.
- 📱 Using a third-party app to make calls, like Google Phone or Truecaller, they can ignore the proximity sensor signals.
- 🔄 Fastboot flashing is an extreme method if the failure is associated with damage to system files.
⚠️ Warning: If the problem persists after the reset and the proximity sensor does not respond to the tests, it is 100% hardware fault.
💡
In 90% of cases, the problem is solved by cleaning the sensor, updating the MIUI or resetting the settings. If the screen goes out even after that, the iron (sensor, plume or display module) is to blame.