Modern Xiaomi smartphones have a complex internal structure hidden from the average user, but for diagnosis and fine-tuning there is a special section known as the engineering menu. Owners of the Redmi 9 model often face the need to check the health of sensors, calibrate the screen or reset the system parameters without completely reinstalling the operating system.
Once inside, you will find a set of tools that are popularly called CIT-It's a test, because it allows you to test each component of the device in isolation, and it can be to check the display for broken pixels, diagnose communication modules, or evaluate the quality of recording sound through a microphone. It is important to understand that work in this section requires caution, since changing critical parameters can lead to unstable work of the gadget.
This article details all the legal ways to log into the hidden MIUI section, explains the purpose of the main menu items, and provides recommendations for the safe use of diagnostic tools. We will look at both standard methods through the Phone app and alternative options if the main method for some reason does not work on your firmware version.
What is the Engineering Menu and Why You Need It
The engineering menu in Xiaomi smartphones, including the popular Redmi 9, is a system utility for hardware tests. The average user rarely looks here, but when you buy a used device or after a phone drops, this becomes an indispensable tool. Here you can run automatic check of all modules, which is much faster and more efficient than looking for malfunctions by pumping in everyday use.
One of the key features is that you can view technical information about the hardware of the device, you can find out the exact model of the installed display, the version of the fingerprint sensor, or the battery status, including the number of charge cycles, which is often hidden in the standard settings interface, but is open for diagnostic purposes.
⚠️ Warning: Changing settings in sections marked as "Single Item Test" or "Version" may cause sensor calibration resets. Be careful when pressing buttons whose value you do not know.
In addition, this interface can reset Bluetooth or Wi-Fi modules, which helps solve connection problems that are not eliminated by a conventional reboot. This is a kind of “deep cleaning” of hardware drivers, which often returns connection stability.
The main way to enter through the phone application
The simplest and most common method of accessing hidden features on Redmi 9 is to use a standard call, which doesn't require any additional software or superuser privileges, but all you have to do is type in a special character combination that activates the hidden mode.
Open the Phone app and go to the dial tab. Enter the following sequence: ##6484##. Immediately after entering the last character () the screen should blink and the CIT (Customer Integration Test) window will open. If the combination does not work, try an alternative option that is often used in older versions of MIUI: ##4636#*.
☑️ Checking before entering
It is important to note that some global firmware versions may not require instantaneous transitions, in which case you may need to press the call button after entering the combination, although 95% of the time the transition is automatic. Make sure you have the original MIUI shell installed, as custom firmware can block this functionality.
Alternative methods of access to CIT-test
If the standard code doesn't work or the keyboard blocks the input of special characters, there are workarounds. Redmi 9 owners can use the built-in diagnostics app that's pre-installed on the system, which is even more visual, since it doesn't require remembering digital combinations.
Find an application called Service & Feedback on your desktop or in the Tools folder. At the bottom of the screen is the Diagnostics tab. By clicking on it, you'll be taken to the same engineering menu where all hardware tests are available, an official path recommended by Xiaomi itself.
What to do if the menu does not open?
Another option for advanced users is to use ADB debugging. By connecting the phone to a computer, you can send a command that will force the desired component of the system to run, which is useful if the touch screen is partially broken and you can't enter the code manually.
adb shell am start -n com.miui.cit/com.miui.cit.CITActivityReview of the main sections and testing of equipment
Once you're successfully logged in, you'll see a list of dozens of items, each of which is responsible for a specific node on your smartphone. You can use a touch screen or volume button to move up and down and a power button to confirm your choice. This is convenient if the touchscreen doesn't work properly.
Let’s take a look at the most important tests to do on Redmi 9 to assess its condition:
- 📱 Touchpanel is a touchscreen test, and the screen is colored in a certain color, and you have to swipe your finger across all the squares, and if the line is interrupted, there's a sensor problem in that area.
- 🎨 Display is a display test that allows you to check the screen for broken pixels, uniformity of backlight and color reproduction by switching monochrome images.
- 🔊 Receiver & Speaker — Audio modules testing. The phone will play test signals through the speaker and main speaker, and record sound from the microphone for subsequent playback.
- 📶 Sim Card: Checks the SIM card readability, shows whether the device sees the SIM card inserted and correctly identifies the SIM card operator.
The Sensor section, where you can calibrate the accelerometer (screen rotation sensor) and the proximity sensor, is particularly noteworthy. If you don't turn off your screen during a conversation or if you have a latency, resetting the calibration in this menu often solves the problem.
| Name of the test | Function | Successful outcome |
|---|---|---|
| Touchpanel | Touchscreen diagnostics | All the cells are painted green. |
| Key | Button checks | Volume and power buttons respond |
| Vibrator | vibrator test | The device vibrates when pressed |
| GPS | Search for satellites | The coordinates and speed are displayed |
| Flashlight | Flash check | The flash lights up and goes out. |
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When conducting a GPS test, it is better to go out to an open space or go to the window, since inside the building the signal can be captured for a long time or unstable.
Resetting and calibration of sensors
One of the most popular features of the engineering menu is to reset the sensor calibration. Over time, especially after falls or a body change, the proximity sensor on the Redmi 9 can start to malfunction, which is manifested in the fact that the screen does not light up when you remove the phone from your ear, or vice versa, it goes out during dialing.
To correct this, look for ProxSensor, inside you'll see the Calibration button, click on it and follow the instructions on the screen (usually you need to close the top of the phone with your hand and then remove it), and after successful calibration, the system will give you a Pass message.
⚠️ Warning: Do not calibrate the sensors unless there are obvious problems with them. Resetting the factory parameters unnecessarily can lead to incorrect operation of autobrightness and turn the screen.
Also available in this section is a full data reset. The QC Test or Clear eMMC button (depending on the menu version) can erase all data from the phone, returning it to factory status. Use this feature only in extreme cases when a normal reboot does not help, and be sure to back up important files beforehand.
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The calibration of the proximity sensor is the most common reason to access the engineering menu, solving 90% of screen problems during calls.