How to change the firmware of the communication module on Xiaomi Redmi

Problems with mobile communication on smartphones Xiaomi Redmi often become an unpleasant surprise for users accustomed to the stable operation of the gadget. SIM-The card, loses the signal in the zone of confident reception or even displays "No network", usually indicates a software failure in the operation of the radio module. In most cases, the culprit is damaged or malfunctioning modem firmware, which controls all wireless interfaces of the phone.

Recovery of a radio part requires careful attention and understanding of the structure of Android software. The communication module (modem) is a separate software component that interacts with the basic equipment of the phone for making calls and mobile Internet. its replacement or flashing is different from a conventional change of the operating system and requires the use of specialized tools like Fastboot or engineering menus.

Before you take action, you need to be clear about the risks. The wrong version of the software can lead to the loss of the unique IMEI identifier, which will make the phone unusable for use in cellular networks. It is critical before you start any manipulations to make a full backup of the data and make sure that the firmware model strictly conforms to the hardware revision of your device. In this guide, we will discuss safe diagnostic and recovery methods.

Diagnostics of problems with the radio module on Redmi

The first step should always be to identify the problem accurately. Don't rush to reflash the device if symptoms indicate a physical antenna failure or damage. SIM-Check if the signal level is displayed, if the mobile Internet is working with Wi-Fi on, and if other phones see your network in access point mode. If the phone writes "Emergency Calls Only" or constantly searches for the network, the probability of a software error is high.

For diagnostics, engineers use a hidden check menu. Enter dialer code ##4636## to get into the testing section. Here you can see the connection status, network type and signal strength. If this menu is empty or displays errors, the problem lies deep in the system. It is also worth checking the baseband version in the About Phone settings. If there is "Unknown", this is a direct indicator that the modem firmware is missing or corrupted.

⚠️ Note: If the network problem persists after resetting to the factory (Hard Reset), the probability of hardware failure increases to 70.

There are several key signs indicating the need for intervention in the modem:

• 📶 The phone does not catch the network of any operator, although SIM-cardwork.
• 📉 Permanent connection breaks 4G/LTE even at full signal level.
• ❌ In the settings "About the phone" in the column "Version of the modem" is displayed «N/A» idle.
• 🔄 An endless reboot cycle when trying to activate mobile data.

Tools and drivers preparation

The success of the operation to replace the firmware of the communication module with Xiaomi Redmi depends on the quality of the workplace. You will need a computer running Windows, since most tools to work with Qualcomm or MediaTek (the main platforms of Redmi) are sharpened for this OS. Linux and macOS may require complex emulation configuration or specific compilers.

The first thing you need to install is drivers. Without them, your computer won't see your phone in the right mode. Qualcomm devices need QDLoader drivers, and MediaTek devices need VCOM drivers. Often they come bundled with firmware, but it's better to install them separately through Device Manager to avoid version conflicts. Make sure that when you connect your phone in boot mode, there are no unknown devices with yellow exclamation marks.

The second important component is the original USB-Cheap charging-only cables don't transmit data, which will cause an initialization connection error. The cable should be short and high-quality, preferably original from a smartphone. ADB and Fastboot, which is the standard for interacting with the Android bootloader.

For the firmware procedure itself, a utility is often used. QPST (for Qualcomm; or SP Flash Tool (for MediaTek), however, in the case of Xiaomi, the most secure and versatile method is to use Fastboot mode with official or custom modem images. Download the archive with the firmware corresponding to your model (codename, for example, cepheus or raphael). The archive must contain the file. NON-HLOS.bin modem.

Search for a compatible version of the modem firmware

Finding the right file is not just a formality, it's a critical step. Modem firmware is tightly tied not only to the phone model, but also to the region (Global, China, EEA) and Android version. Trying to install the modem from the Chinese version on the global version can lead to the failure of LTE frequencies used in your country. Always check the region of the device in the code under the battery or in the settings.

Search files best on proven resources, such as the official forum Xiaomi (MIUI Forum), profile branches on XDA Developers or specialized sites-aggregators firmware. you need a full firmware archive (Fastboot ROM), from which you will extract only the necessary partition, or already the modem file, if it is available separately.

The structure of the firmware files may vary. In some cases, the modem is a separate modem.img file or NON-HLOS.bin. In others, it is part of a large archive. If you download the full firmware, you will need to unpack it (sometimes you need to unpack it in several steps, since the archives can be in.tgz or.zip format).

It is important to understand the difference between regions:

• 🌍 Global – Global version, supports most frequencies worldwide.
• 🇨🇳 China - Chinese version, some frequencies may be missing B20 (important for Russia and Europe).
• 🇪🇺 EEA — version for the European Economic Area.
• 🇮🇳 India is a specific version for the Indian market, often with restrictions.

⚠️ Warning: Never flash a modem from another phone model, even if the processors are the same.This is guaranteed to lead to a brick or loss IMEI.

Firmware procedure via Fastboot

The most reliable way to replace the firmware of the communication module is to use the Fastboot mode. This mode allows you to write data directly to the memory sections of the phone, bypassing the operating system. To enter this mode, turn off the phone completely, then press the Volume Down and Power buttons simultaneously, holding them until the logo with a hare in a hat-eared (or Fastboot inscription) appears.

Connect your phone to your computer. Open the command prompt (CMD) or PowerShell in the folder where the modem file is located (for example, modem.img). First, check the connection with the fastboot devices command. If you see the serial number of the device, the connection is set correctly. If the list is empty, check the drivers and the cable.

Now you can start recording. The command depends on the structure of your file. If you have a modem.img file, the command will look like this:

fastboot flash modem modem.img

If you use a binary file NON-HLOS.bin (specific to Qualcomm), the command may differ, but most often Xiaomi uses the standard modem partition name. The process will take a few seconds. After successful recording, you need to restart the device with the command fastboot reboot.

In some cases, especially when you move between regions or Android versions, you may need to clear user data. This is done by the fastboot erase userdata command or fastboot wipe data. Attention: this will delete all your photos, contacts and apps. Do this only if you understand the consequences.

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If the phone went into a cyclic bootloop after firmware, try pressing the power button for 15-20 seconds for a forced reboot, or re-enter Fastboot and flash the full system image.

IMEI Recovery and Calibration

The biggest danger when working with the modem firmware is the loss of the unique IMEI identifier. This number is “sewn” in a special protected partition of memory (often called Persist or EFS). If during the firmware process or due to an error, this partition is damaged or overwritten by zeros, the phone will lose the ability to register on the network.

Check status. IMEI If you see zeros, scratches, or an error message instead of numbers, you can type *#06#, then the partition is damaged. IMEI software without prior backup (QCN-The file made before the problem is almost impossible on modern Xiaomi devices due to the enhanced protection of the bootloader.

However, if IMEI is preserved but communication is not working well, it may require calibration of antennas. On modern smartphones, this process is automatic, but sometimes helps reset network settings. Go to Settings → Connection and Sharing → Reset Wi-Fi, mobile networks and Bluetooth. This action is secure and does not delete personal files, but resets access points and Wi-Fi passwords.

For users with an unlocked bootloader, there are tools like the MTK Engineering Mode (for MediaTek) that allow you to manually switch your preferred network type, for example, you can force LTE Only mode if the phone constantly falls off in 3G. But you need to be careful: in LTE Only mode, incoming calls may become unavailable if VoLTE technology is not configured.

⚠️ Attention: Change IMEI Using a number on another device is illegal in many countries. use recovery tools only to return your original number.

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Preserving the EFS/Persist partition is the number one priority. Before any experimentation with the modem, make sure you have a backup of this partition or are prepared to risk losing warranty and communication.

Frequent errors and methods of their solution

The firmware process rarely goes perfectly smoothly, especially if you're doing it for the first time. One of the most common mistakes is FAILED (remote: device is locked). It means that the phone bootloader is locked by the manufacturer. Fastboot firmware on Xiaomi often requires an unlocked bootloader, which is officially done through a MIUI application and wait for 7-168 hours.

Another problem is the FAILED error (remote: partition flashing is not allowed). This is anti-Rollback firmware. Xiaomi implements security mechanisms that prevent rollbacks to older versions of Android or modems. If you try to flash an old modem to a new version of the system, the process will be blocked. Always use files of the same version or newer.

Users also face a situation where the speaker has lost sound or Wi-Fi has stopped working after the firmware has been installed, which suggests that the Persist partition, which stores calibration data for all sensors and modules, has been damaged. Unfortunately, it is extremely difficult to restore this partition without a factory backup from a specific device (with the same serial number), in which case only a complete firmware reflash through the Mi Flash Tool in Clear All mode helps.

Let’s look at the typical error codes:

• 🚫 FAILED (remote: flash write failure: A problem with your phone’s memory or cable.
• 🔒 FAILED (remote: device is locked – you need to unlock the boot loader.
• ⬇️ FAILED (remote: version check failed - an attempt to roll back to the old version).
• 📉 FAILED (remote: partition table update failed) - damaged partition table, requires flashing the entire system.