Smartphone owners often face the need for deep diagnostics of devices that go beyond standard settings. The engineering menu in Xiaomi Redmi Note 9 is a hidden part of the system, designed to test hardware components and set up radio modules. Access to this interface allows you to check the quality of communication, the state of the touch screen, the operation of speakers and microphones without installing third-party software.
However, it is worth noting that the MIUI installed on the Redmi Note 9 is significantly different from stock Android, which imposes certain limitations. Many classic codes running on other devices can be blocked by the manufacturer for the sake of user safety. However, there are proven ways to activate diagnostic modes, which we will discuss in detail in this article.
Before you start manipulating system settings, you need to be aware of the risks. Incorrectly changing the parameters in the CIT section or the engineering menu can lead to malfunctioning of communication modules or a complete reset of network settings. This guide will help you safely access hidden functions and diagnose your Redmi Note 9.
What is the engineering mode on the Redmi Note 9
Engineering mode is a special software interface built into the operating system of a smartphone. On Xiaomi devices, it is often implemented through the CIT (Customer Inspection Test) application, which is used in factories to check the build quality. Unlike conventional settings, this mode gives access to hardware at a low level.
The main purpose of this section is to run hardware tests, where you can run vibration checks, calibrate proximity and light sensors, and test the color of the display, and for the average user, it's the ability to identify a malfunction before you go to the service center.
⚠️ Warning: Changing the parameters in the partitions associated with radio frequencies (Radio Info) can lead to loss of network signal or inability to make calls.
It's important to distinguish between the engineering menu and the developer mode. The developer mode is designed to debug apps and connect to a PC, whereas the engineering menu works directly with the physical components of the device. On the Redmi Note 9, both sections are accessed in different ways, and you shouldn't confuse them.
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The engineering menu on the Redmi Note 9 is primarily a CIT diagnostic tool, not a means to unlock hidden system functions.
Preparation of the smartphone for diagnosis
Before attempting to enter hidden areas, make sure your Redmi Note 9 is fully functional in basic functionality. Battery charge should be at least 40-50%, as some tests, such as screen checks or vibrations, consume a significant amount of power.
It is recommended to close all background applications so that they do not interfer with the launch of diagnostic utilities. If the device has third-party launchers or programs for managing calls, it is better to temporarily return to the standard MIUI interface.
It's worth preparing. SIM-Because part of the engineering menu is connected to network configuration, there is no SIM-The card can hide some menu items or render them inactive.
☑️ Check before entering the menu
The main way to enter through a secret code
The fastest and most effective method of activating the diagnostic interface on the Redmi Note 9 is to use the same diagnostic interface. USSD-This method does not require superuser rights (Root) and works on most versions of the firmware. MIUI.
Open the standard Phone app, which you usually make calls through, go to the dial tab and enter the following character combination:
##64663##Once you enter the last character, the menu should open automatically. You don't need to press the call button. If it's successful, you'll see a list of test pieces with the names of the components in English. That's the CIT menu.
In some cases, if the code doesn't work right away, try entering it slowly, making small pauses between character groups, and also make sure that the dialer doesn't activate the blocking functions of extraneous numbers that can intercept the input of special characters.
What if the code doesn't work?
Alternative activation methods through settings
If you can't enter code for some reason or you don't get it, you can use the built-in functionality. On the Redmi Note 9, the test is often hidden under the About Phone section, which is more secure and guaranteed to work on all official firmware.
To do this, go to Settings → About Phone. Find the line “MIUI Version” or “Keronel Version” (depending on the shell version) and quickly click on it 5-7 times. The screen may notify you that you have become a developer, or immediately open the menu of additional tests.
Often, on Xiaomi devices, the tests are built directly into the MIUI Version menu. Once you click repeatedly, you will see a list of available checks, similar to what the code calls, and you can check GPS, gyroscope and other sensors.
Another option is to use the Service & feedback app, which is pre-installed on the system, and often has a Device Testing section or similar, duplicate functions on the engineering menu inside the app.
| Entry method | Necessary rights | Available functions | Risk of error |
|---|---|---|---|
| USSD code (#64663##) | No. | Complete (CIT) | Low. |
| Settings (About the phone) | No. | Basic | Minimum |
| Application Service | No. | Expanded | Low. |
| ADB team | USB debugging | Systemic | Medium. |
Overview of the main functions and tests of CIT
Once you've successfully logged in, you'll see a list of tests, each item corresponding to a specific Redmi Note 9 module, and let's take a look at the most useful ones for everyday diagnostics.
The Touch Panel section allows you to check the sensor, and when you run the test, the screen will suggest that you draw lines in certain areas, which is a great way to identify dead zones or multi-touch problems that are not noticeable in normal use.
The Receiver and Speaker test checks the audio speakers, first playing a quiet sound (conversational speaker), then a loud one (main) to help determine why the person you are talking to is not hearing well or why the sound is lost while playing media.
- 🔋 Battery: Displaying the real status of charge and voltage.
The Vibrator test, which is a test that's designed to trigger vibrations, so you can measure the vibration's strength and the absence of any extraneous sounds, which can indicate wear and tear.
Diagnostics of signal and network problems
One of the most important features of the Redmi Note 9’s engineering menu is to check the radio module, and if you notice that the phone is not catching the network well, switching between towers for a long time, or losing signal altogether, this section will be the most useful.
Some firmware versions have a code ##4636## that opens the test menu, and you can see the network type (LTE, 3G, 2G), the signal level in dBm, and the connection state, but on global versions of MIUI, this code is often blocked.
If the standard menu is not available, you can try to switch the network mode forcibly. CIT Choose the Sim 1 or Sim 2 test, where information about the current communication standard can be available, sometimes manually selecting the preferred network type through the standard settings helps: → SIM-maps and mobile networks → Type of network.
⚠️ Warning: Do not try to change values in fields where you are not 100% sure.Resetting network settings may require flashing the device in the service center.
For a deep signal level diagnosis, use the RF Test (if available in your version of CIT).It shows technical reception parameters such as RSSI and RSRP. The normal value for LTE is the range from -80 to -100 dBm. Values below -110 dBm indicate an extremely weak signal.
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If the phone loses network after resetting, try the “Select Band” option in the engineering menu (if available) and force only LTE (Band 3, 7, 20 for Europe) to be enabled, eliminating 2G/3G.
Frequently encountered problems and their solution
Redmi Note 9 users often find themselves in a situation where nothing happens after entering the code, which may be caused by the default replacement of the Phone app by a third party (such as Google Phone or Truecaller), in which case the code simply will not be recognized by the system as a command.
The solution is to temporarily install Xiaomi’s standard call app or use alternative login methods through settings, and the problem may lie in the region of the device: Chinese firmware versions may have different access codes than global ones.
Another common mistake is to accidentally reset the proximity sensor calibration, so if you've stopped dimming your screen during a conversation after testing in the engineering menu, you need to recalibrate it, which is usually available in the same CIT menu at Prox sensor.
In case your phone starts to work unstable after you've been using hidden menus, the most reliable way to get things back to normal is to reset them to factory settings.