Xiaomi Mi 9T QCN (Davinci) 4G Fix

How to Install Xiaomi Mi 9T QCN?

What is QCN?

QCN is the section where the IMEI and network information of devices with Qualcomm processors are collected. The device used also refers to the information in this section about network-related settings at the first power-on. Information such as IMEI and meid number, network calibration values ​​are included in QCN.

If devices with QCN problems do not receive a network or only provide 2G network, if there is a problem in 3G and 4G gsm bands, there is an error in this file. Again, by making changes on the same file or by restoring the stock QCN file, the malfunctions can be resolved. If there is a network problem after QCN, if the IMEI cannot be read, the problem is caused by the complete or partial failure of the BASEBAND integrated, which cannot process this information. QCN file does not contain wifi and MAC values.

Xiaomi Mi 9T QCN

How to Reset Xiaomi Mi 9T EFS?

In order to do this, the phone’s bootloader must be unlocked. If it’s not clear, just continue with the eng rom step below. Before doing this, make sure to back up the EFS partition with TWRP. If you have the umt dongle Qcfire program to reset efs, this job is very easy.

Boot the phone in fastboot mode, reset the efs partition with the wipe efs BL option from the qcfire Xiaomi special partition. After the Efs partition is reset, you can start the QCN installation process.

How to Upload QCN File?

There are two ways to upload the QCN file to the phone.

  • By installing eng rom on the phone
  • By granting root access

What is Eng rom?

Eng rom is short for Xiaomi Engineer Rom. Eng rom is used during production, to measure the performance of the device, to test the phone. It is not suitable for end-user use. This is because there are no security updates in the ENG rom. When you install eng rom, the phone’s diag port becomes active.

To install Eng rom, you need to open the phone and put the phone in EDL mode with the test point. We will share the process of how to put the phone to edl mode in a different topic.

When the Diag port is active, you can easily load the QCN file with QPST or umt dongle Qcfire. When you’re done with the eng rom, don’t forget to install the stock rom on the phone.

Root Method

To perform the root process, the phone’s Bootloader must be unlocked. In cases where the bootloader is not unlocked, you can install eng rom and perform the process. After installing the appropriate twrp on the phone, boot the phone in recovery mode. You can find the addresses required to delete Redmi 9T efs here. After doing this, the efs partition is now reset. Now it’s time to open the diag port with root.

How to open diag port with adb & fastboot tools?

First, download the Minimal ADB and Fastboot tools. Start the CMD command prompt application in the adb&fastboot folder. From the developer options of the phone, activate the “Debug Mode” and type the following commands on the cmd screen in order.

adb shell


setprop sys.usb.config diag,adb

Now the phone’s diag port is open and it communicates with the computer through this port. You can restore the edited QCN file with programs such as QPST or umt dongle.

The Xiaomi Mi 9T QCN 4G fix file that we shared has been tried. The phone’s network worked at full performance.

This QCN file is only valid for Xiaomi Mi 9T QCN (Davinci). Do not try on other models. Don’t forget to format the efs partition before uploading the QCN file.

You can download the Redmi K20, Mi 9T (Davinci)-4g-fix QCN file Click here.

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