How to go to the engineering menu on Xiaomi Mi 9T: secret codes and features

The Xiaomi Mi 9T (also known as the Redmi K20 in some regions) is a popular smartphone with powerful hardware and flexible MIUI firmware. But even experienced users don’t always know that there’s an engineering menu hidden under the hood of the device — a tool for deep customization of hardware components, testing modules, and even overclocking performance. However, access to it requires caution: one incorrect parameter can turn a phone into a “brick”.

In this article, you will find all the working ways to log into the engineering menu on the Mi 9T, including codes for different firmware versions, decryption of key partitions and unique features not available in standard settings, and a security checklist to avoid fatal errors in experiments.

What is an Engineering Menu and Why You Need It

The Engineering Menu (or Engineer Mode) is a hidden firmware section designed to:

• 🔧 Diagnostics of hardware components: checking the camera, speakers, sensors, battery.
• ⚡ Radio Frequency Settings: Network Selection 2G/3G/4G, hand-tuning.
• 📡 Communication testing: signal level analysis, search for “dead zones” of coverage.
• 🔄 Calibrations of sensors: gyroscope, accelerometer, proximity sensor.
• 🚀 Overclocking/performance restrictions: changing processor frequencies (requires root).

On the Xiaomi Mi 9T, the engineering menu is especially useful for:

• 📶 Improved network reception in low signal conditions (e.g. basements or outside the city).
• 🔊 Sound settings through speaker amplifier adjustment (risk of damage!).
• 📱 Verification of components (e.g. whether the battery is original).

⚠️ Note: Change of settings in the Hardware Testing section → Audio can cause physical damage to speakers. Do not raise the values above the factory without special equipment!

Official and unofficial ways of entry

The Mi 9T has three proven ways to get into the engineering menu, depending on the firmware version and root rights status:

The safest way is to use USSD-For example, code ##4636### will open a menu with battery information, usage statistics and network tests, but for full access you need code ##36446337## (not available on all versions). MIUI).

Step-by-step: how to enter through USSD-code

This method does not require root rights and works on most versions of MIUI 10-14.

Backup your data (via Settings → About Phone → Backup)

Charge your phone at least 50%

Prepare a notebook for recording factory values (it will be useful for rolling back changes)

Close all background applications-->

1. Open the Phone application (standard dialer).
2. Enter the code: ##36446337## Make sure that the * and # characters are entered correctly - on some keyboards they can be replaced with other characters.
3. If the code worked, you'll see the EngineerMode (MTK) menu. If not, try the alternative code: ##4636##
4. To exit the menu, use the Back button or restart the phone.

⚠️ Note: Some of the firmware Xiaomi Mi 9T After entering the code, the menu does not open, but the message “Connection problem or invalid” appears. MMI code." This means that the manufacturer has blocked access. In this case, try the method with ADB (described below).

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If USSD-The codes are not working, check if there are blocking apps on the phone (like Truecaller or Firewall.

Alternative method: Entry through ADB

If USSD-The codes are not working, you can use Android Debug Bridge (ADB). This method requires a computer and enabled debugging. USB.

Instructions:

1. Activate Developer Mode: Settings → About Phone → MIUI version (click 7 times).
2. Enable USB debugging in Settings → Additional → For developers.
3. Connect your phone to your PC and open the command line (Windows) or terminal (macOS/Linux).
4. Enter the commands in turn: adb devices (make sure the device is determined) adb shell am start -n com.mediatek.engineermode/.EngineerMode

If the team doesn’t work, try an alternative:

adb shell am start -a android.intent.action.MAIN -n com.android.settings/.DevelopmentSettings

Decoding of key sections of the engineering menu

The interface of the engineering menu on the Mi 9T is divided into several tabs.

1. Hardware Testing

Here are collected tests of hardware components:

• 🔋 Battery – check the charge, temperature, battery voltage.
• 📸 Camera – Camera test (front and main), autofocus check.
• 🎤 Audio – setting up microphones and speakers (cautiously with changing values!).
• 📡 Network - signal analysis GSM/CDMA/LTE.

2. Telephony

Section for setting up mobile communication:

• 📶 Band Selection – Manual selection of frequencies 4G (useful for improving communication in roaming).
• 🔄 PLCI — information about the current cell and operator.
• 📞 Call Settings – Configure call settings (e.g. enable VoLTE).

3. Connectivity

Tests of wireless modules:

• 📶 Wi-Fi – check the speed, signal strength, channels.
• 📱 Bluetooth – test of connection and sound quality.
• 📍 GPS — Checking accuracy of navigation (useful for Google Maps or Yandex.Navigator).

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The most dangerous sections are Hardware Testing → Audio and Telephony → Band Selection. Changes here can lead to hardware breakdowns or network loss.

What can be broken and how to avoid it

The engineering menu is a lot of things, but the risks are high.-5 Mistakes that make Mis 9T brick-in»:

1. Changing the radio frequency settings (Telephony → Band Selection) - Incorrect frequency selection can lead to the loss of the network forever.
2. Increase the volume of the speakers above factory values (Hardware Testing → Audio) Risk: burnout of the amplifier.
3. Reset the calibration of the sensors (gyroscope, accelerometer) and then the phone may misguide the orientation in space.
4. Disabling critical services in the Connectivity section, for example, deactivating the IMS will make calls impossible.
5. Changing the battery settings (Hardware Testing → Battery) can cause false charge data or accelerate battery degradation.

How to minimize the risks:

• 📝 Record factory values before changes (take screenshots).
• 🔄 Don’t change the settings at random – look for guides for a particular model (Mi). 9T).
• 🛠️ Use a backup copy (created through the TWRP or Mi PC Suite).

Hidden features of the engineering menu for Xiaomi Mi 9T

In addition to standard tests, the Mi 9T engineering menu contains unique features:

1. Activation of the diagnostic port: In Hardware Testing → USB, you can enable Diag Port mode, which allows you to connect to the phone through specialized software (for example, QPST or MTK Droid Tools), this is necessary for deep firmware or IMEI recovery.
2. Color Rendering: Hardware Testing → Display has hidden RGB calibration options, you can adjust your white balance or increase saturation (but this will reduce battery life).
3. Touch Screen Test: Hardware Testing → Touch Screen has a tool to check multi-touch and sensitivity. Useful if the screen does not respond well to touch.
4. Hidden battery information: Hardware Testing → Battery displays real battery wear (in percent) rather than rounded data from standard settings.

On the Xiaomi Mi 9T, there is a unique Hardware Testing → Fingerprint section in the engineering menu that allows you to test the fingerprint scanner under the screen, where you can check the recognition speed and calibrate the sensor if it becomes worse after the update.

FAQ: Frequent questions about the engineering menu