Xiaomi Mi 9S approximation sensor: where is located, how does it work and what to do when it breaks down

Xiaomi Mi 9S (Also known as the Mi 9. SE in the global version) - compact flagship with AMOLED-And there's a special thing about the proximity sensor, which is the sensor that automatically turns off the screen when you call, but where is it located? Why does it stop working? And how do you check it without disassembling your smartphone?

This article will help you understand the sensor’s design, its precise location under the glass, and provide practical tips for diagnosing and troubleshooting. We’ve analyzed the Mi 9S circuits, reviewed service center reports, and gathered up-to-date data so you can solve the problem yourself or understand when to contact the wizard.

Where is the proximity sensor in Xiaomi Mi 9S: photo and diagram

In the Xiaomi Mi 9S, the proximity sensor is integrated into the top of the screen next to the speaker and the front camera, specifically, a small circular hole to the right of the selfie camera, if you look at the phone in the standard position (the speaker on top).

It's important to understand that the sensor is physically an infrared sensor, made up of two elements: a emitter (sends an invisible beam) and a receiver (fixes a reflection), both of which are hidden under glass, so they're visually visible only as a small black speck.

On the Mi 9S motherboard, the sensor is labeled PROXIMITY SENSOR and connected to the main controller via a flexible display plume, which means that when you replace the screen, make sure to check the sensor's performance - its plume is easily damaged.

How the proximity sensor works and why you need it

The main function of the sensor is to turn off the screen during a phone conversation when you hold the smartphone to your ear, which prevents accidental pressing of the cheek or ear on the sensor, and also saves battery power.

1. The emitter sends out an infrared beam.
2. The beam bounces off an object (like your ear) and returns to the receiver.
3. The microcontroller analyzes the signal and turns off the screen if the object is closer than 3-5 cm.

The Mi 9S uses a digital sensor (as opposed to the analogue ones in the older models), which makes it more accurate but also sensitive to contamination, for example, if dust hits the glass in the sensor area or the protective film is improperly pasted, it can fire falsely.

In addition to calls, the proximity sensor is involved in:

• 📱 Pocket mode: locks the screen when the phone is in your bag or pocket.
• 🎧 Automatic audio route switching: when brought to the ear, the sound switches from the speaker to the headphones (if connected to the ear).
• 🔒 Smart Lock: unlocks the device when you hold it in your hand (paired with a gyroscope).

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If the sensor is triggered too often (e.g. while reading), try calibrating it through the engineering menu. To do this, dial ##6484## and select Proximity Sensor.

Signs of malfunction of the proximity sensor

How do you know if the sensor is out of order?

• 📵 The screen does not go out during the call, which is why you accidentally press the buttons with your cheek.
• 🔄 The screen spontaneously turns off even when the phone is on the table.
• 📱 Apps (such as WhatsApp or Telegram) do not switch the sound to the speaker when the phone is taken away from the ear.
• 🔋 The battery quickly goes down due to the constant operation of the sensor in the background.

Sometimes the problem is not with the sensor itself, but with the software, for example, after the MIUI update, the calibration settings may get lost.

1. Open the Phone app and dial ##6484##.
2. Select Proximity Sensor (proximity sensor).
3. Close the sensor with your finger – the value should change from 5 (no obstacle) to 0 (there is an obstacle).

If the values do not change or show incorrect data (for example, always 0), this indicates a hardware malfunction - damage to the plume, oxidation of the contacts or failure of the sensor itself.

⚠️ Warning: If the sensor stopped working after the phone fell, do not try to disassemble the Mi 9S In this model, the display module is glued to the frame, and if you disassemble it in a careless way, you can damage the fingerprint plume or the front camera.

Why the proximity sensor breaks down: top-5 cause

Analysis of reports from service centers shows that in Xiaomi Mi 9S, the proximity sensor most often fails for the following reasons:

The most common problem is pollution, because even a thin layer of dust on the glass in the sensor area can block the infrared signal, and often the fault is with the wrong notch of the sensors, for example, if the film closes the sensor completely, it stops "seeing" the obstacles.

The second most popular cause is plume damage. In the Mi 9S, the sensor is connected to the motherboard via a flexible display cable. If you disassemble it in a sloppy way (for example, when you change the battery or screen), the plume can be torn, in which case the sensor ceases to respond fully, and in the engineering menu shows the same value (usually 5).

How to fix the proximity sensor: step-by-step instructions

If tests show that the sensor is faulty, try the following steps (from simple to complex):

Clean the sensor area with alcohol and soft cloth|Check the safety glass – does it cover the sensor?|Calibrate the sensor through the engineering menu|Update. MIUI last-minute|Reset the settings to factory (if the problem is software)|Contact the service (if the sensor is physically damaged)-->

Step 1. Clean the sensor

Take an isopropyl alcohol (at least 70%) and a cotton swab. Gently wipe the area around the front camera and speaker. Don't press hard - the Mi 9S glass is thin and can crack. After cleaning, check the sensor through the engineering menu.

Step 2. Calibration

If the sensor is responding but not correctly (e.g., it is triggered too late), calibrate:

1. Dial ##6484##.
2. Select Proximity Sensor.
3. Press Calibrate (calibrate).
4. Follow the instructions on the screen (usually close the sensor with your finger for 5 seconds).

Step 3: Checking the protective glass

Remove the protective film or glass and check the sensor without it. If the problem disappears, then the accessory was installed incorrectly. When buying a new glass, choose models with a precise notch for the sensors (for example, from the brands Spigen or AmFilm).

Step 4: Resetting settings

If the sensor started to glitch after the MIUI update, try resetting the settings:

1. Go to Settings → About the phone → Reset settings.
2. Select Reset all settings (does not delete files, only settings).
3. After restarting, check the sensor.

⚠️ If after all the manipulations the sensor still does not work, and in the engineering menu shows 5 regardless of obstacles - this is a sign of hardware breakdown. In this case, you need to replace the plume or the sensor itself, which is impossible to do at home (need a soldering machine and experience with microelectronics).

The cost of repairing the proximity sensor in Xiaomi Mi 9S

The cost of repair depends on the cause of the malfunction and the region, and on average in Russia and the CIS the current prices (for 2026) are as follows:

Important: Xiaomi’s official service centers don’t do the sensor replacement separately, just with a display or a plume, so if the problem is in the sensor itself, and not in the plume, repairs can be more expensive than buying a used Mi 9S.

You can save money by contacting informal workshops, but there are risks:

• 🔧 Use of non-original parts (the sensor can quickly fail again).
• 📉 Loss of tightness (after disassembly, the phone may no longer be waterproof).
• ⚠️ Lack of job security.

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If the proximity sensor breaks down due to a drop or moisture, repairs may not be cost-effective – in this case, it makes more sense to consider buying a new phone, since the Mi 9S is no longer supported by official updates.

Frequent questions about the proximity sensor Xiaomi Mi 9S