Why the screen does not go out when talking on Xiaomi Redmi Note 9 Pro: a complete guide to diagnosis and repair

You bring the Xiaomi Redmi Note 9 Pro to your ear, you start a conversation -- but the screen persists in glowing, responding to touch, and even draining the battery in vain -- and it's not only annoying, it creates risks: random taps, quick discharge, and it's just uncomfortable to talk to a bright display in your face. 80 percent of the time, it's the wrong settings of the proximity sensor or software failures, but sometimes the root of the evil lies deeper, in hardware malfunctions.

This article will help you diagnose the cause (from simple sensor contamination to plume damage) and fix it without contacting the service — if possible. We will analyze the unique features of the Redmi Note 9 Pro (for example, the features of the STK3311 sensor in this model), provide screenshots of the MIUI menu, and also tell you when self-repair is dangerous and it is better to go to the master immediately.

1. Checking the proximity sensor: why it doesn't work

The proximity sensor is a small sensor next to the front camera that detects when you hold your phone to your ear. The Redmi Note 9 Pro uses the STK3311 (or similar chip from Lite-On), which sometimes crashes. The first thing you need to do is check it manually.

For this:

• 📱 Open the Phone app and type ##6484## (test code for the phone) MIUI).
• 🔍 In the menu, select Proximity Sensor (approximation sensor).
• 🖐️ Close the sensor with your hand – the value should change from 5.00 to 0.00.
• 🚨 If the numbers don’t change, the sensor is defective or contaminated.

If the test shows that the sensor is working, but the screen is still not going out, the problem is the system settings.

2. MIUI settings: what could have gone wrong

Often the problem lies in power saving options disabled or lost call parameters. In MIUI 12/13/14 (depending on the firmware version of your Redmi Note 9 Pro), the path to settings may differ, but the general logic is the same.

Follow the instructions:

1. Go to Settings → Applications → Application Management.
2. Find the phone and open its settings.
3. Make sure that options are included: 🔄 Autoturning the screen (affects the work of sensors) 📵 Turn off the screen during the call 🔋 Battery Optimization (must be disabled for Phone app)

Screen → Sleep mode

15 seconds.

If the screen continues to glow after these manipulations, the problem is deeper, perhaps firmware or physical damage.

3. Software glitches: when a reboot or reset helps

MIUI malfunctions or application conflicts can block the normal operation of the proximity sensor, starting with the most innocuous reboot:

• 🔄 Press the power button and select Reboot.
• 📱 After turning on, check if the screen goes out when you call.

If it doesn’t work, try cleaning the cache:

1. Go to Settings → About the phone → Memory.
2. Click Clear Cache (not to be confused with Settings Reset!).
3. Reset the device.

In extreme cases, the reset to factory settings will help, but before that:

⚠️ Warning: Reset will delete all data, including photos and contacts. be sure to back up via Settings → Additionally. → Backup or Mi Cloud backup.

4. Sensor or plume damage: when disassembly is needed

If all the software methods have been tried and the screen is still on, it's a hardware problem. In the Redmi Note 9 Pro, the proximity sensor is located next to the front camera and connected to the motherboard via a flexible plume.

You can only clean the sensor yourself if you're confident.

1. Turn off the phone.
2. Remove the protective glass/film (if any).
3. Wet the cotton swab in isopropyl alcohol (at least 90%).
4. Gently wipe the area around the sensor (don’t press hard!).
5. Let dry for 10-15 minutes before turning on.

⚠️ Warning: Do not use conventional medical alcohol or wet wipes - they leave a wiring and can damage the coating of the sensor. If after cleaning the problem remains, do not try to disassemble the phone yourself: in the Redmi Note 9 Pro, the sensor plume is very fragile and easily tears.

5. Conflict with protective glass or cover

So, you might think that the case can affect the sensor, and in practice, it's easy. In the Redmi Note 9 Pro, the proximity sensor is located close to the edge of the screen, and if you:

• 📱 The protective glass is too thick or with a metallized layer, it blocks the infrared signal of the sensor.
• 🛡️ High-sided case closes the sensor area.
• 🧲 Magnetic holders (for example, for fastening in the machine) create interference.

The solution is simple:

1. Remove the cover and the safety glass.
2. Call your phone and check if the screen is going off.
3. If yes, replace the accessories with thinner ones (for example, glass with a thickness of ≤ 0.2 mm).

Accessories rarely take into account the location of sensors in specific models, so even “original” cases from Xiaomi can cause problems. If you use oleophobic armored glass, try temporarily removing it – sometimes it causes failures.

💡

Before buying a new protective glass, check in the description if there is a notch under the proximity sensor. For the Redmi Note 9 Pro, glass marked "Full Cover Notched" or "Sensor-Friendly" will fit.

6. firmware update: MIUI bugs and how to fix them

Some versions of MIUI (especially 12.0.1-12.5.4) had a bug that ignored the proximity sensor during calls. Xiaomi released patches, but if your Redmi Note 9 Pro hasn’t been updated in a long time, the problem may be in outdated software.

How to update:

1. Go to Settings → About the phone → System update.
2. Click Check for updates.
3. If a new version is available, download and install it (be sure to connect to Wi-Fi and charge your phone at least 50%).

If automatic updates don't work, you can try manual firmware via Fastboot or Recovery, but it's risky:

⚠️ Warning: The wrong firmware can turn your phone into a brick. If you've never done this before, you better contact the service. For the Redmi Note 9 Pro (codenamed joyeuse), official firmware can only be downloaded from the site. MIUI Download.

After the update, don't forget:

• 🔄 Reboot the phone.
• 📱 Check the sensor with the test code ##6484##.
• 🔧 Reset the settings of the Phone application (in Settings) → Annexes → Application management → Phone. → Warehouse → Drop it).

💡

If you still have a problem after the MIUI update, try to roll back to the previous stable firmware version. To do this, download the archive with the desired version and swipe through Recovery (the instructions are on the 4PDA forums).

7. Alternative solutions: if nothing has worked

If all of the above methods fail, radical measures remain:

1. Software-based shutdown: With the Sensor Disabler app (requires root), you can force the proximity sensor to turn off, but then the screen will only go out on the sleep timer, which is a temporary solution, because when you call, the screen can still interfere.
2. Use of third-party calls: Install an alternative call app (like Google Phone or Truecaller) that sometimes has better sensors, but note that in MIUI, third-party calls can conflict with system services.
3. Hardware repair: If the sensor or plume is physically damaged, you just have to carry the phone to the service.The average cost of replacing the proximity sensor for the Redmi Note 9 Pro is 1800–3000 ₽ (depending on the region and service).

Before agreeing to repair, ask the master to conduct a full diagnosis - sometimes the problem lies not in the sensor, but in the motherboard, and then the repair will cost more.

FAQ: Frequent questions about the problem