How to Open the Engineering Menu on Xiaomi Redmi Note 9: A Complete Guide with Codes and Warnings

Xiaomi Redmi Note 9 smartphones (including Pro, Pro Max and Pro versions) 9S) They hide a powerful tool under the hood for fine-tuning, the engineering menu, which is also known as Engineer Mode or the engine mode. MTK Engineer Mode, which allows you to change network settings, test hardware components and even unlock hidden functions MIUI. However, access to it requires caution: one incorrect action can lead to loss of communication, resetting settings or even “bricking” the device.

Many users are looking for ways to get into this menu to improve communication, calibrate the sensor or check the actual characteristics of the battery. But the official documentation of Xiaomi does not mention its existence - no wonder, because it is designed for engineers and developers. In this article, we will analyze all the working ways of entering (including hidden codes for different versions of the firmware), explain which settings can be changed without risk, and which - only at your own risk.

⚠️ Warning: Changing the settings in the engineering menu can disrupt the device, cancel the warranty and even make the phone unusable.All actions you perform at your own risk. If you are not sure of your skills, you should consult a specialist.

What is an engineering menu and why you need it on the Redmi Note 9

Engineering menu is a service mode built into the firmware of smartphones based on chipsets MediaTek (as in Redmi Note). 9 helio-processor G85/G95) Qualcomm provides low-level access to hardware components, which allows for the:

🔹 Test equipment: check the operability of speakers, microphones, cameras, sensors and even the battery with the output of real data (for example, voltage and capacity without taking into account software constraints) MIUI).

🔹 Set up the network: change the parameters 4G/5G, switch frequency bands, test the speed of the Internet without the influence of the operator.

🔹 Calibrate sensors: Correct errors of the gyroscope, compass, or proximity sensor if they are not working properly.

🔹 Unlock hidden functions: for example, activate Dirac HD Sound on unaccompanied models or enable debugging USB proofless.

On the Redmi Note 9, the engineering menu is especially useful for:

• 📶 Network Signal Improvements – If the phone is not catching the connection in your area, you can manually select the optimal frequency here.
• 🔋 Diagnostics of the battery - the real capacity may differ from the declared 10-15% after a year of use.
• 🎤 Microphone checks are useful if people complain of poor hearing.
• 📱 Sensor testing – if the screen responds to late or spontaneous touch.

⚠️ Note: Some of the options in the engineering menu (e.g. Band Selection for the network) can be blocked by the operator. SIM-The card will cause a complete loss of communication!

Official and unofficial ways to log in to Engineer Mode

There are several ways to open the engineering menu on the Redmi Note 9, but not all of them work on the latest versions. MIUI. We tested them on firmware. MIUI 12.5–14 (Android 10–12) and identified the most reliable.

📌 The main method (works on 90% of devices):

1. Open the Phone app.
2. Enter the code ##4636##
3. If the code didn’t work, try the alternative: ##36446337## (for MediaTek chipsets).
4. After entering, a menu with tabs will open Information about the phone, Battery use, etc. – this is Engineer Mode.

🔧 Alternative methods (if the codes do not work):

• 🔄 Through Developer Settings: Activate Developer Mode (click 7 times on Version) MIUI In Settings → About the phone, then in Settings → Additionally. → For developers, find Local Data Transfer and hold it for 5 seconds.
• 📱 Using third-party applications: Utilities like MTK Engineering Mode (for MediaTek) or Shortcut Master can open menus but require root rights.
• 🖥️ Through ADB: Connect your phone to your PC, activate Debugging USB The command is: adb shell am start. -n com.android.settings/.DevelopmentSettings

⚠️ Note: Some firmware Xiaomi blocks access to the engineering menu through codes. If nothing happens after entering, check if there are any applications from the operator (for example, My MTS or Beeline Services) on the phone that may restrict functionality.

Engineering menu: what can and can not touch

Once you've entered successfully, you'll see a few tabs, and we'll take a look at the most important and dangerous ones.

📊 Main sections and their purpose:

🔍 The most useful functions for the average user:

• 📊 Battery check: In Battery, you'll see the actual capacity in mAh, not the percentage of charge. If the value is much lower than the passport value (for example, 3500 instead of 5020 mAh), the battery is worn out.
• 📶 Manual network selection: In Telephony → Network Select can be forced to switch to 4G Only or 3G Only if the automatic mode is not stable.
• 🔊 Speakers and microphones test: Hardware Testing → Audio check if one of the microphones or speakers is silenced.

🚫 What can not be done under any circumstances:

• ❌ Change the settings in Telephony → BandMode without knowing the frequencies your operator supports.
• ❌ To make changes in NV Items – This can lead to loss IMEI.
• ❌ Activate Factory Reset in the engineering menu is a complete reset to factory settings without the possibility of cancellation.

How to improve network signal through the Engineering Menu

One of the most popular features of Engineer Mode is manual network settings, which is true if your Redmi Note 9 is not catching communication in certain places (for example, in the subway or in the country).

📡 Instructions for signal optimization:

1. Open the Engineering Menu and go to Telephony → Network Select.
2. Choose yours. SIM-card (if two of them).
3. Press Run Ping Test, and this will show the current network latency. If the ping is above 200 ms, the connection is unstable.
4. Go back to Telephony and select BandMode.
5. See what ranges your operator supports (for example, for MTS it is a range that is not a range of the ranges). B3 (1800 MHz), B7 (2600 MHz), B20 (800 MHz)).
6. Only mark the ranges that are actually used in your region (you can find out on the operator’s website or through applications like NetMonster).
7. Save the settings and restart the phone.

📌 Example of optimal settings for Russia (MTS, Beeline, MegaFon):

• 📶 LTE Band: B3, B7, B20 (baseband 4G).
• 📞 WCDMA Band: B1 (2100 MHz).
• 🚫 Turn it off. TD-SCDMA and CDMA — They are not used in Russia.

💡

If the connection is lost after the changes, return the settings in BandMode to factory (press Restore Default) and restart the phone. If that does not help, you will have to reset the network settings in the main Android menu.

⚠️ Note: If you choose a non-existent range (e.g, B28 For Yota, the phone will stop catching the network at all! Before you change, make sure you know the exact frequencies of your operator.

Checking and calibrating the battery through Engineer Mode

Over time, lithium-polymer batteries in smartphones lose capacity, and the charge controller begins to show inaccurate data. In the engineering menu, you can see the real state of the battery without embellishing it from the side. MIUI. Here's how to do it:

🔋 How to check the actual capacity of the battery:

1. Open the engineering menu and go to Battery.
2. Pay attention to the parameters: Voltage - current voltage (normal: 3.7-4.2 V). Temperature - temperature (optimum: 25-40°C. Capacity is the real capacity in mAh (compare with passport).

If the capacity is below 80% of the declared (for example, 3800 mAh instead of 5020), the battery is severely worn out.

🔄 Calibration of the charge controller (if the phone is turned off when the charge controller is switched off) 20-30%):

1. Discharge the phone before automatically shutting down.
2. Connect the charger and turn on the device.
3. Go to the engineering menu immediately. → Battery.
4. Click Battery Calibration (if any) or manually reset the stats to Battery Stats.
5. Charge your phone to 100% without interruption.

💡

Calibrating the battery through the engineering menu only helps if the problem is a downed charge meter. If the battery is physically worn out (swelled or the capacity fell below 60%), it needs to be replaced.

⚠️ Some “craftsmen” advise to dump Battery Stats through the ADB team

adb shell dumpsys battery reset

Redmi Note 9

constant display of 0% charge

Sensor and sensor testing: when it is needed

If your Redmi Note 9 has “glitches” with the screen (self-pressing, non-functioning zones) or sensors work incorrectly (for example, autoturn does not work), the engineering menu will help identify the problem.

🔍 How to test the touch screen:

1. Go to Hardware Testing → Touch Screen.
2. Press Start Test and a grid will appear on the screen.
3. Put your finger all the way down the line, and if there's a break in the track, the sensor's broken.

🛠️ Calibration of sensors (if they show incorrect values):

If the tests show failures, try recalibrating:

1. In the engineering menu, select Sensors. → Calibration.
2. Press Reset Calibration for the problem sensor.
3. Place your phone on a flat surface and wait until it is completed (usually). 10-20 seconds).

⚠️ Warning: If the sensors are getting worse after calibration, return the factory settings to the Restore Default in the same section. Some sensors (such as the Hall Sensor for cases) may stop functioning altogether after manual changes!

Frequent Mistakes and How to Avoid Them

Working with the engineering menu is fraught with consequences if you don't know the nuances.-5 Errors made by Redmi Note users 9, And they explained how to prevent them.

❌ Mistake 1: Reset IMEI

In the Telephony section → SIM Info has a Restore button IMEI. Pressing it will nullify it. IMEI, And the phone will lose the ability to call, and you can only fix this through firmware or service centers!

❌ Mistake 2: Change NV-parameters

Telephony. → NV Browser stores critical network settings, and editing them without knowing the specifics will result in loss of network login (the phone will no longer see). SIM-map).

❌ Mistake 3: Incorrect calibration of the battery

If you interrupt the calibration process (e.g., turn off the phone while charging), the charge controller may start showing an incorrect percentage (e.g., 100% at real 60%), and this can only be corrected with a full discharge/charge of the cycle.

❌ Mistake 4: Disabling important sensors

Sensors can deactivate sensors (e.g. Light Sensor for automatic brightness) and then stop working until the settings are reset.

❌ Error 5: Change the frequency of the processor

Some versions of Engineer Mode have a section. CPU Settings: Increased frequency will overheat and cause rapid wear on the chipset, and lowered frequency will cause brakes.

💡

Before any changes to the engineering menu, back up your data through Settings. → System system → Backup. It won't save you from hardware breakdowns, but it will save your photos and contacts.

FAQ: Answers to Frequent Questions