Xiaomi Mi 9 is constantly rebooting: a complete repair guide

The situation of a flagship smartphone suddenly turning into an unmanageable device, making the owner nervous, is familiar to many. If your Xiaomi Mi 9 is constantly rebooted, it can be caused by a software conflict, a system failure or a hardware malfunction. Cyclical restart (bootloop) is a protective mechanism, but sometimes it becomes a trap from which it is difficult to get out without intervention.

In most cases, the problem lies in the damage of system files or overflow of memory, but we can not exclude the wear of the battery, which is typical for devices released in 2019. Before carrying the gadget into the service, it is worth trying a set of software recovery methods that often bring the device back to life.

Below we will discuss step-by-step instructions, ranging from simple actions to complex firmware manipulations, and carefully following the algorithm will help you avoid data loss and unnecessary repair costs.

Primary diagnosis and safe regimen

The first step should always be to try to download Safe Mode, a system state that shuts down all third-party applications, allowing you to determine if a newly installed software or update is the culprit.

To enter this mode on the Mi 9, you need to wait for the Mi logo to appear during boot and press the volume button. If the phone successfully boots and stops going into the rebuke, then the problem is in one of the applications.

⚠️ Warning: In Safe Mode, the interface may look unusual and some features may not be available.

If the device is stable in this mode, remove all newly installed programs or those that have access to system resources. Often the culprits are launchers, antiviruses or modified versions of popular services.

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If the phone reboots immediately after the logo is turned on and does not allow you to enter the menu, go to the next section with Recovery Mode.

Using Recovery Mode for Resetting

If the system doesn't boot at all, you'll need access to the Recovery menu, which is a special firmware section designed for diagnostics and recovery, and you can get there on Xiaomi smartphones by turning off the device and holding down the power and volume buttons at the same time.

Once you enter the menu (where you often need to choose English and click Wipe Data), you will be given a choice: save the data or delete it. The Wipe All Data option will completely clear the internal memory, returning the phone to a factory state.

Once the cleanup process is complete, the system will suggest a reboot, which can take up to 10 minutes to start as the file tables are first set up, and do not interrupt this process even if the screen goes out.

Problems with the battery and charger

Xiaomi Mi 9 is equipped with a battery capacity of 3300 mAh, which is not the largest indicator for a modern high-powered processor. Over time, the lithium polymer power source degrades, losing the ability to give current under load.

The symptoms of a worn-out battery often manifest themselves in cyclic reboots, especially when the charge drops below 40-50%.The phone may turn off in the cold or when running "heavy" applications, and then immediately try to turn on again.

• 🔋 The phone turns off when 20-30% charge.
• 🔋 Reboots only occur when the camera or games are running.
• 🔋 The back cover in the battery area is swollen or warmed.

Also worth checking is the cable and the power supply. Unstable voltage can cause a power controller to malfunction, which the system perceives as a critical error. Try using the original Type-C cable and Quick Charge-enabled unit.

Hardware malfunctions: button and plumes

One common but common reason for the endless reboot cycle is the sticking of the power button. Mechanical wear or moisture causes the contact to close permanently, causing the processor to go into reboot.

To test this hypothesis, gently press the power button or tap on the end of the device slightly, and if the cycle patterns change, it's probably the mechanics that are the problem, which requires replacing the button plume at the service center.

⚠️ Warning: Don't try to disassemble the phone yourself unless you have experience.The Mi 9 uses a glass back cover that is very easy to crack when removed.

Another hidden cause is the battery plume or display going away, and after a fall, the contact may be disrupted, causing short circuits, and the circuit board's diagnosis requires opening and visual examination of the connectors.

Fastboot and Mi Flash flash flash flashing

If the software reset doesn't work, the last software method is to completely reflash, and to do this, the phone is switched to Fastboot mode (clamping the volume button when you connect the cable to the PC) and connected to the computer.

You will need the Mi Flash Tool and the official firmware in.tgz format for your model (codename cepheus). clean_all, to completely re-mark the memory.

fastboot devices


fastboot getvar all

This method eliminates file system errors that are not treated by standard reset, but if the Xiaomi Mi 9 is rebooted after flashing, the probability of hardware failure of the motherboard is 99%.

When repairs are needed in the service

There are a number of symptoms that indicate that software methods are powerless: If the phone heats up at the top of the case (where the processor is located) before the logo appears, this is a sign of a short circuit on the board.

It is also worth thinking about repairing if the phone responds to charging (the indicator lights up), but does not show signs of life when connecting to a PC (eMMC/UFS).

• 🛠️ The smartphone is warming up even when turned off.
• 🛠️ The smell of chemicals or fumes appears.
• 🛠️ The screen flashes stripes before turning off.

Repairing the motherboard, especially replacing the processor or memory, is often not cost-effective for the 2019 model, but replacing the battery or plumes can extend the life of the device.

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If a complete flashing and battery replacement did not help, the problem lies in the “iron” – most likely in the dump of the processor or memory due to overheating.