Engineering menu on Xiaomi Mi 9: hidden features and tests

Owners of flagship smartphones like the Xiaomi Mi 9 often seek to squeeze out the device as much as possible beyond the standard user interface. One of the most powerful tools for diagnosing and fine-tuning the system is an engineering menu that is hidden from the eyes of the average user. This section allows you to conduct deep hardware diagnostics, calibrate sensors and check the health of communication modules without installing third-party applications.

Access to hidden features can be required in a variety of situations, from authenticating components after purchasing a used device to fixing specific software failures. In this article, we will detail how to safely enter engineering mode on the Xiaomi Mi 9, what codes are working up to date and what tools may be needed if standard methods are blocked by the manufacturer.

It's worth noting that tampering with system settings requires caution and understanding the consequences. Incorrectly calibrating sensors or changing the parameters of the radio module can lead to malfunctioning of the device. However, if you are willing to act carefully, there are opportunities that are not available in the usual Settings menu.

What is hidden engineering mode Xiaomi Mi 9

Engineering menus, often referred to as CIT (The Customer Integration Test, or Factory Mode, is a set of diagnostic utilities built directly into the firmware of a smartphone. On the Xiaomi Mi 9, this section is used by engineers in the factory to finalize the build quality before packaging. For the user, this is an opportunity to check how well the touchscreen works, whether the colors are displayed correctly on the screen. AMOLED-Matrix and whether the device catches a signal in problem areas.

The main value of this mode is that it is independent of the Android operating system as we know it. Even if the system loads with errors, low-level tests are often available, making the engineering menu an indispensable tool in the diagnosis of hardware malfunctions.

The functionality is divided into separate modules, each of which is responsible for a specific component:

• 📱 Display Test: Check broken pixels, uniformity of backlight and matrix reaction to different colors.
• 📡 Radio & Network: Testing of modules GSM, LTE, Wi-Fi and Bluetooth, including signal strength checks (RSSI).
• 🔊 Audio Test: Diagnostics of microphones, conversational speaker and multimedia sound.
• 📍 Sensor Test: Calibration of accelerometer, gyroscope, proximity and illumination sensor.

⚠️ Warning: Changing the parameters in the sections marked as "Factory" or "Calibration" without the presence of special equipment (signal generators, color calibrators) can lead to irreversible deterioration of the device performance.

Methods of entry through system dialing number

The easiest and fastest way to get into the hidden menu is to use special ones. USSD-codes through a standard bell. In Xiaomi smartphones with a shell MIUI This method is often the main one, although in the latest firmware versions some codes may be blocked.

To start, open the Phone app and dial the combination ##6484##. If the code is valid for your version of MIUI, the smartphone will automatically switch to the CIT menu, bypassing the call screen. This is the main gateway to hardware tests.

There is also an alternative code ##4636## that opens the phone information testing menu, which has less in-depth settings, mostly related to network connectivity and usage statistics, but is useful for quick checks of IMEI and network status.

It is important to understand that on global firmware versions (Global ROMs), some codes may not work due to regional constraints, in which case the system will simply ignore the input or issue a connection error message.

Using ADB for Advanced Access

If standard codes don’t work, as is common on newer versions of MIUI 11, 12 and higher, the only working option is to use USB debugging and the ADB command line, which requires connecting a smartphone to a computer.

First, you need to activate the developer mode. Go to Settings. → About phone and quickly press 7 times on the item Version MIUI, until you have an activation notification. Then, in the advanced settings, turn on USB-debugging.

Connect the Xiaomi Mi 9 to your PC with a cable and open the command line in the folder with the ADB installed. To start the engineering menu, use the following command:

adb shell am start -n com.android.settings/.HardwareInfoActivity

This command forcibly triggers the system settings activity that is responsible for hardware information, and in some cases, it may be necessary to run a specific test application through the com.miui.cit package.

The advantage of ADB is that it bypasses the locking of the bell interface, but if the manufacturer has completely removed the relevant components from the firmware, even this method may not give full access.

Running through hidden system applications

Deep inside the Xiaomi Mi 9 resides file system, a special application responsible for testing that usually doesn't have an icon in the launcher.It can be tried to run through the application management menu or third-party launchers.

Try to find a list of all applications called CIT or Testing. If the label is hidden, you can use the Activity Launcher app, which allows you to see all the activity of the system. Find the com.miui.cit package in the list and select CitActivity activity.

The good thing about this method is that it doesn't require a computer after you first install the activity launcher, and you get direct access to a test interface similar to what codes call.

It is worth remembering that running hidden activities through third-party launchers on new versions of Android may be limited by system security policies requiring additional permissions.

Diagnostics of the display and touch screen

One of the most popular features of the engineering menu on the Xiaomi Mi 9 is to check the display. AMOLED-matrix installed in this model are prone to burnout and the appearance of broken pixels over time.

In the Display or Color Bar section, the screen is consistently filled with red, green, blue, white and black. Carefully examine the surface in bright light: any spots that differ in hue or dots that do not change color indicate a matrix defect.

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To check the touchscreen, use the Touchpanel section, swipe your finger across the grid to make sure each cell responds to touch, which will help identify dead zones.

Multi-touch check is also available here, and the engineering menu will show you the exact number of simultaneous touches that the controller registers. For the Mi 9, the normal indicator is support for up to 10 simultaneous touches.

⚠️ Warning: Don't try to calibrate the color temperature or gamut in the engineering menu without a professional colorimeter. Broken factory settings can make the color reproduction unnatural and it will be extremely difficult to fix it software.

Testing of communication modules and GPS

Communication problems are a common reason to contact the service. The engineering menu allows you to estimate the real signal power that your Xiaomi Mi 9 modem receives. Unlike the standard "sticks" in the status bar, here you will see the exact numerical values in dBm.

To check, go to Sim Card Test or Radio, where you can force the network modes to switch (LTE only, 3G only), which is useful in areas of uncertain reception, where the phone constantly "jumps" between standards, consuming the battery.

The GPS test is worth a special attention, and you run the module and the phone will try to determine the coordinates.

• 🛰️ Satellites: Number of visible satellites.
• 📶 SNR: Signal/noise ratio for each satellite.
• 📍 Accuracy: Positioning accuracy in meters.

If the SNR values are low even under ideal conditions, this may indicate a hardware malfunction of the antenna module or its plume.

Frequently Asked Questions (FAQ)

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The engineering menu is a powerful diagnostic tool, not a toy. Use it to check the condition of the device before you buy or to identify the causes of malfunctions, but avoid random changes in calibration settings.