Users switching from personal computers or laptops to the Android platform often look for a classic BIOS (Basic Input/Output System) in their smartphones. In the mobile world from Xiaomi, as in other Android gadgets, the familiar BIOS graphical shell does not exist in the form that everyone is accustomed to on Windows. Instead, the system offers a set of specialized diagnostic and boot modes, such as Fastboot, Recovery and CIT engineering menu.
Understanding the difference between these modes is critical to proper device management. If you want to change boot order, check the state of hardware components, or perform low-level flashing, these are the tools you need. The CIT Engineering Menu (CitTest) is a direct functional analogue of the BIOS, providing access to hardware tests without booting the main operating system. The following sections of the article will describe in detail how to activate these hidden functions.
Differences Between BIOS, Fastboot and Recovery on Android
Unlike desktop computers, where the BIOS is stored on a separate motherboard chip and has its own interface, Xiaomi smartphones share these functions among several bootloaders. The main analogue is the Fastboot mode, which allows you to interact with the device at a low level before Android launch. It is through this mode that the bootloader is often unlocked or custom recaps are installed.
Another important component is Recovery Mode, which is a recovery section that is used to reset to factory settings (Wipe Data) or install system updates manually. Although it looks like a text-based menu, it is limited to operating system maintenance and does not provide access to fine iron settings such as sensor calibration or battery voltage checks.
The third level is the engineering menu, which I'll talk about later, and it's the closest thing to the BIOS concept, because it allows you to test individual modules: screen, speaker, vibrator, sensors, but it's often hidden from the average user to avoid accidental software failure.
- 🔹 Fastboot – a mode for flashing, unlocking the bootloader and deep diagnostics.
- 🔹 Recovery – Recovery Environment for Data Reset and Software Update.
- 🔹 CIT / Engineering Mode - a set of hardware tests, analogue BIOS.
⚠️ Attention: Interference with the bootloader or changing the parameters in the engineering menu without proper knowledge can lead to the inability to turn on the device (brick).
How to activate CIT Engineering Menu through code
The easiest and safest way to get into the analogue BIOS on smartphones Xiaomi, Redmi and Poco – the use of special USSD-This method doesn't require a computer connection or root permissions, but you need to open the standard phone application and enter the sequence of characters.
Enter the code ##6484## or ##4636### on the dial keyboard. Once you enter the last character, the system automatically recognizes the command and switches the screen. You don't need to press the call button, otherwise you'll just try to call that number. If the code is entered correctly, the CIT menu will open.
This menu contains a list of all the tests available, you can consistently check the display (by clicking on points), microphone, speakers, proximity sensor and other components, and it is the perfect tool for checking the phone before you buy from your hands or after you fall.
What if the code doesn't work?
To exit the menu, just press the back button or complete the testing process if it has been started. Remember that some tests, such as a vibration test or a screen test, may require your confirmation to proceed to the next step.
Enter Fastboot Mode for Advanced Users
Fastboot is a more powerful tool than CIT, and is often used by enthusiasts to modify the system. On Xiaomi devices, it is entered by a combination of physical buttons when the device is off, analogous to logging into the BIOS via a Del or F2 key when a PC starts.
To enter the Fastboot, turn off your smartphone completely. Then press and hold the Volume Down button. Without releasing the Volume Down button, press the Power button for a brief moment. Hold the Volume button pinched until an image with the Fastboot logo or a picture of a hare fixing an android appears.
You'll see on the screen the status of the bootloader. If you say Locked, it means the bootloader is locked by the manufacturer, and you can't flash it without official unlocking. Unlocked status tells you that the device is ready for modifications. It's usually enough to hold the power button for a long time (about 10-15 seconds) until it vibrates and reboots.
☑️ Check before entering the Fastboot
It is important to note that in Fastboot mode, volume navigation usually does not work, since it is not a full menu, but a waiting mode for commands from the PC. ADB/Fastboot driver.
Using Recovery Mode for Resets and Updates
Recovery mode on Xiaomi is also often confused with BIOS, although its features are more specific. There are two types of Recovery: standard (Stock) and custom (for example, TWRP). The standard menu has limited functionality and is controlled by volume buttons (up/down for selection, power button for confirmation).
To enter Recovery on most Xiaomi models, you need to turn off the phone, press the Volume Up button and the power button. Hold them until the Mi logo appears, after which the power button can be released, continuing to keep the volume until the menu appears.
In the main menu, you'll see several options, including Reboot, Wipe Data and Connect with MIAssistant. The last item allows you to connect to your computer for firmware through the Mi Flash Tool. Be careful: the Wipe Data item completely deletes all user data, returning the phone to a factory state.
| Regime. | Button combination | Substantive function | Risk of data loss |
|---|---|---|---|
| Fastboot | Vol Down + Power | Firmware, unlock. | Low (no action) |
| Recovery | Vol Up + Power | Reset, update | High (at Wipe) |
| CIT (Engineering) | Code ##6484## | Iron tests | Absent. |
⚠️ Warning: Recovery Wipe Data is irreversible. Make sure you have a backup of important photos and contacts before performing this operation.
Debugging through ADB: access to hidden settings
For those who need access to some BIOS-like settings, there is an ADB (Android Debug Bridge) tool, which is a console utility that allows you to send commands to your phone from your computer, and it needs to activate the developer mode to work.
Go to Settings → About Phone and tap 7-10 times on MIUI Version (or OS Version) until you see “You’re a developer.” Then go to Settings → Additional Settings → For Developers and turn on the USB Debugging Toggle.
Connect your phone to your PC with a cable. On your computer, you can type commands in the command line (terminal), for example, the adb reboot bootloader command will force the phone to restart to Fastboot mode, and the adb reboot recovery command will force the phone to restart mode, which is an alternative way to log in if the physical buttons are faulty.
adb devices
adb reboot bootloader
adb shell am start -n com.android.settings/.HardwareInfoUsing ADB requires caution. Introducing incorrect commands into the adb shell console can lead to deletion of system files. However, for the average user who wants to simply check the status of the device, the commands adb get-serialno or adb reboot will be safe and informative.
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Use the original. USB-Cheap charging cables often don't have data lines, which means the computer won't see the phone in mode. ADB or Fastboot.
Diagnostics and testing of components at CIT
Back to the CIT menu, because it's the closest analogue of the BIOS to testing the health of the hardware, and in this section you can find tests for each component, for example, the Touchpanel test will ask you to swipe your finger along the lines on the screen, checking the sensor response across the area.
The Receiver test will play the melody, and the Microphone will record your voice and play it back for validation, and there are also tests of the accelerometer (gyroscope), where you put your phone on a flat surface, and the light sensor, which is an indispensable tool when buying a used device.
If a test fails (for example, the sensor can’t see a touch in the corner, or the speaker is wheezing), it indicates a hardware malfunction, and unlike software failures that are treated by flashing, such problems require parts to be replaced at the service center.
- 📱 Touchpanel – Checking responsiveness and dead screen zones.
- 🔊 Audio – check the main and conversational speakers, microphone.
- 📡 Sensor – calibration of proximity, light and gyroscope sensors.
Don't be alarmed if some items on the CIT menu are labeled "Fail" before testing begins, the status changes to "Pass" only after passing a specific test, the main thing is to carefully read the instructions on the screen during the test.
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CIT-Menu is the only safe way to check the physical condition of the phone components without disassembling the device and specialized equipment.