How to check Xiaomi before buying: step-by-step guide 2026

Buying a Xiaomi smartphone from hand is a great way to save money, but only if you know exactly what to look for. Even a seemingly perfect device can hide critical malfunctions, from a bloated battery to swapping parts. In this article, 15 proven steps to help identify all possible problems before you transfer money.

We’ll look at not only obvious things like scratches on the screen, but also hidden flaws that vendors often keep silent about, like how to verify the originality of the Mi Account or why a bright light camera test can save you from buying a phone with a fake module. All instructions are relevant to models 2018–2026 years, including the Redmi Note line, POCO and flagship Xiaomi 13/14.

Pay special attention to the battery and software lock sections, two of the most common Xiaomi used-us issues that can make your phone useless a month after you buy. If you’re in a hurry, use the interactive checklist in the middle of the article.

1.External inspection: what gives the "broken" phone

Start by visually inspecting the case, and take the phone from different angles to the light, so you can see the microcracks on the glass and the repairs.

• 🔍 The gaps between the case and the screen - if they are uneven (more than 0.5 mm), the phone fell or disassembled. AMOLED-screens (e.g. Xiaomi 12 Pro) where the slightest bias leads to display defects.
• 🎨 The color of the body is different, and if the back cover or frame is different in shade from the rest of the body, it's a sign of replacement.
• 🔋 Battery bloating -- put the phone down on a flat surface with the screen. If it swings or goes up one of the corners, the battery needs to be replaced urgently. On Redmi Note models 9/10 bloating often starts at the lower right corner - check it with your finger for softness.

Feel free to ask the seller to remove the case, which may be chipped or corrosion from moisture. If the phone is pasted with film, ask to lift it, under it often hide cracks or scratches on the glass.

⚠️ Warning: If a seller refuses to remove a cover or film, arguing that it is "safety of the goods", this is a reason to be wary.

2. Screen and touch panel test: 5 mandatory checks

The screen is the most expensive component to repair, so you can make the most of the time you can diagnose it.

1. Open the Settings. → Display. → Colors and temperature and select "Standard" mode".
2. Run a video with a monochromatic background (black, white, red, green, blue) on YouTube. The broken pixels will be visible as colored dots.
3. Check the uniformity of the lighting in a dark room - on AMOLED-screens often show "burnout" (blurred spots from static interface elements).

To test the sensor, use the Touch Screen Test app (available on Google Play) to show:

• 📱 Dead zones – areas that do not respond to touch.
• 🔄 False positives – if the screen spontaneously presses buttons.
• ⏱️ Response delay – on cheap Chinese screens after replacement can reach 100 ms (normal – up to 30 ms).

Check the automatic brightness:

1. Include it in Settings → Display. → Automatic brightness.
2. Point the camera of the other phone to the screen and dramatically change the lighting (for example, close the light sensor with your hand). On a serviceable phone, the brightness should adjust smoothly without jerking.

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If the seller says the screen is "almost original," ask for a replacement check, which is a cheap Chinese equivalent with a reduced color rendering and sensitivity in 95% of cases.

3. Battery: How not to buy a phone with a "bomb inside"

The battery is the most worn component in a smartphone, and even if the phone looks like new, its battery could lose 50 percent of its capacity.

Method 1: Through the Menu of the Engineering Test

1. In the phone app, type ##4636##.
2. Select Battery Information.
3. Compare the Battery Health score with the table below:

Method 2: Real-time test

• 🔋 Fully charge your phone (up to 100%).
• 📱 Turn off Wi-Fi, mobile data and start the video offline at maximum brightness.
• ⏳ Take the discharge time to 1%. For comparison: the new Redmi Note 12 Pro+ It should last at least 6 hours, and Xiaomi 13 Lite – 7 hours+ hours.

If the phone is discharged in 2-3 hours - this is a sign of either a worn-out battery or a software failure (for example, a virus mining cryptocurrency in the background). → Annexes → Launched.

⚠️ Warning: If the phone is heated (more than 45)°C), this may indicate a power controller malfunction, often masked by turning off fast charging in settings. Check the temperature with your hand after 15 minutes of charging.

4. Checking the completeness and originality of parts

Fake parts are used by Xiaomi, most often forged:

• 📷 Main camera (especially in models with 108 MP or 200 MP).
• 🔊 Chinese speakers lose up to 40% of their volume.
• 📡 Antenna modules (problems with network signal).

How to detect a fake:

1. Camera: Take a picture of a text document (like a check) from 30 cm away. On fake modules, the letters will be blurred at the edges and the colors will be unnaturally saturated. Compare it to the photo on another phone.
2. Speakers: Turn on a bass track (like "Seven Nation Army" - The White Stripes) at maximum volume. The original speakers should not wheez or distort the sound.
3. Body: The original Xiaomi parts have a microscopic engraving with a serial number (see below the magnifying glass) that is not on the fakes.

Check it out. IMEI phone:

1. Dial *#06# and a 15-digit code will appear on the screen.
2. Compare it to the number under the battery (if the case is removable) or on the box.
3. Check it out. IMEI on imei.info – if the phone model does not match the stated one, it is 100% fake or “overstitched” device.

5. Software verification: viruses, locks and firmware

Even if the phone is apparently functional, it can be blocked by a previous owner or infected with malware. Start by checking Mi Account:

1. Go to Settings → Xiaomi account.
2. If there's someone else's account attached, ask the seller to untie it in front of you, and after the detachment, the phone should reboot.
3. If the seller says he forgot his password, that's a reason to refuse to buy it. ~3000 ₽ and not always possible.

Virus testing:

• Install Malwarebytes or Dr.Web Light from Google Play.
• Run a deep scan. Look at the apps with Chinese characters in their title, which means that the phone is being imported gray.
• Check the list of device administrators in Settings → Passwords and security → Device administrators, there must be no unknown software.

Firmware diagnostics:

If the phone was flashed to custom firmware (like LineageOS), it can cause problems with updates and sensors.

1. Go to Settings → About Phone → MIUI version.
2. If the version ends with Global, EEA or RU — The presence of China or Developer indicates an unofficial version that may contain spyware.

6. Testing cameras and sensors: what the sellers are silent

Cameras at Xiaomi often suffer from two problems: blurring (due to fake modules) and artifacts (defective matrix damage).

Main camera test:

• 📸 Take a picture of a piece of paper with text in good light. On the original camera, the letters will be clear even at the edges.
• 🌃 Take a photo in a dark room with the flash on. On the fake modules appear purple spots or "lights".
• 🔍 Close the image 100% - on the fakes will be visible "squares" (artifacts of compression), which are not in the original photos.

Front camera test:

Take a selfie with Portrait Mode enabled. On fake modules, the background blur doesn't work properly (e.g., eats hair or ears). Also check for autofocus: if it's missing, the camera is definitely unoriginal.

Sensor check:

Launch the Sensor Test app (available on Google Play) and check:

• 🧭 Gyroscope and accelerometer -- turn the phone in different directions. The arrows should follow the movement smoothly.
• 📡 Approximation Sensor – During a call, the screen should go out when you hold the phone to your ear.
• 💡 Light sensor – when you cover the top of the phone with your hand, the brightness of the screen should decrease.

If a sensor doesn't work, it can be either a software problem (the firmware crashed) or a hardware problem (damage when it fell), in the first case, resetting will help, in the second case, only repair.

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If a vendor refuses to take pictures in front of you or says "the camera is just dirty" is a sure sign of a fake, Xiaomi's original modules don't lose clarity from dust.

7. Network and communications check: why a phone may not catch a signal

Communication problems are one of the most difficult to diagnose malfunctions, and they may not show up immediately, but a few days after purchase.

Mobile network test:

• 📶 Check the signal level in areas with poor coverage (for example, in the basement or elevator). If the phone shows 0-1 division, mientras otros dispositivos tienen 2-3, esto indica un problema con la antena.
• 🔄 Switch between modes 2G/3G/4G/5G In Settings → SIM-maps and mobile networks, if the phone doesn't catch 4G or constantly switching to 3G, It's a sign of modem malfunction.
• 📞 Call another phone and check the quality of the connection. Wheezing, cliffs or echoes indicate problems with the microphone or antenna.

Wi-Fi and Bluetooth test:

• 📶 Connect to a Wi-Fi network at a distance of 10+ If the speed is below 10 Mbps with a stable signal, the Wi-Fi module is a problem.
• 🔊 Connect your wireless headphones and listen to music. If the sound is interrupted or there is interference, it is a sign of a malfunction of the Bluetooth chip.

Pay special attention to models with support 5G (for example, Xiaomi 12T or Redmi K50). Often, the sellers are silent that 5G-The modem burned out due to overheating to check:

1. Put it in. SIM-support-card 5G (For example, from MTS or Tele2).
2. Go to Settings → SIM- Cards and Mobile Networks → Network Type and select 5G.
3. If the phone does not find the network 5G in the coverage area, the modem is defective.

8. Additional checks: what is often missed

There are defects that sellers don't talk about because customers rarely check them.

Connector test:

• 🔌 Put the charger on and swing the cable in different directions. If the phone is charging, it's not. USB-C ragged.
• 🎧 If the sound is lost when the plug moves, the 3.5mm connector (if any) is faulty.

Vibration check:

Enable vibration in Settings → Sound and vibration and check:

• If the vibration is intermittent or too weak, the motor is worn out.
• If the phone vibrates spontaneously - this is a sign of a short circuit on the board.

Overheating test:

1. Run a heavy game (such as Genshin Impact or Call of Duty Mobile) at maximum graphics settings.
2. After 15 minutes, check the temperature of the case at the back (near the processor).°C. If the phone is heated to 50°C and above, that's a sign:

Water and moisture check:

Even if the phone didn't sink, he could have been in the rain.

1. Get the tray for you. SIM-Check the card and check for rust.
2. Light the flashlight in the connector USB-C — There should be no oxidation (greenish coating) inside).
3. If the phone has a moisture indicator (like the Redmi Note 10), check its color: red or pink means contact with water.

If the seller refuses to provide this data, there is a high risk that the phone is stolen.