Fix Unknown Baseband & Lost IMEI on Xiaomi Redmi Note 4 (MTK Version)

Contents

I reviewed Xiaomi Redmi Note 4 weeks ago and so far, it has been a really great phone. It works great with most 4G LTE networks in Nigeria, but since Spectranet is what I use most these days, I thought locking the phone to band 40 through MTK Engineering Mode would make things better. Well, I was wrong and things went really, really bad:

All SIM cards stopped working.
I lost IMEI on both SIM slots.
Baseband version started showing “unknown.”

Basically, the phone became useless. As far as I know, there’s no Xiaomi service center in Nigeria and I had no choice than to try fixing this all by myself. After going through forums, I finally fixed the issue. There are basically two major steps involved.

Flashing Fastboot ROM with SP Flash Tool.
Restoring NVRAM and writing IMEI using Maui META.

Prerequisites

Before getting started, you need to download all these:

Latest Xiaomi Redmi Note 4 Fastboot ROM (Global Stable version)
SP Flash Tool
MediaTek USB drivers /
Maui Meta Tool
WinZip

Again, you need to do the following:

Disable Driver Signature Enforcement on Windows. This comprehensive guide shows how to do this on Windows 7, Windows 8 and Windows 10.
Enable USB Debugging from Developer Options on your Xiaomi Redmi Note 4. You need to go to Settings > About phone > Tap MIUI version 7 times to enable Developer Options. Then go to Settings > Additional Settings > Developer Options > Turn on USB Debugging.
Install the downloaded MediaTek USB drivers.
install WinZip.

You are now ready to get started with the first step.

Step A: Flashing Fastboot ROM with SP Flash Tool

1. Unzip SP Flash Tool and run flash_tool.exe as Administrator.

2. Unzip the Fastboot ROM you downloaded earlier with WinZip.

3. Click on Download Agent and select MTK_AllInOne_DA.bin from SP Flash Tool folder.

4. Click on Scatter-loading and select MT6797_Android_scatter.txt from the unzipped ROM folder.

5. Disconnect your phone from the computer if it’s already connected and shut down the phone.

6. Select Format All + Download from the drop-down menu. Now click on the Download button.

7. Hold the volume down key and plug in the microUSB cable end to your phone. If you get BROM ERROR: STATUS_DA_EXCEED_MAX_NUM, plug in the phone without holding the volume down key.

8. The flashing should start. Another possible error is STATUS_SEC_IMG_TOO_LARGE. The only way to resolve this is by getting a smaller CUST.IMG file. For Xiaomi Redmi Note, you can download this, replace the one inside the unzipped ROM folder and start all over again.

9. After a while, the process should complete.

At this point, you can turn on the phone. It’s going to take a while before it boots (like 5 minutes), but we’re not done yet. You still need to shut down the phone again and we can move to the second step.

Step B: Restoring NVRAM and writing IMEI using Maui META

1. Install Maui Meta Tool and launch. Select Options and check Only Preloader Port.

2. ~~Be sure the drop-down on the left is set at IMEI download and~~ the one on the right is set at USB COM. Now click on Reconnect.

3. With your phone turned off, insert the microUSB cable into the phone and wait for a while. Your phone should be detected after the Mi logo is displayed. By the way, you don’t need to press the power button as instructed. After the phone is detected, set the drop-down menu on the left to IMEI download.

4. A new window should come up. Click on Change NVRAM Database File, then click NO to select your NVRAM file.

4. Now go to the ROM download folder and select an EDB file named MDDB_InfoCustomAppSrcP_MT6797…. This is the NVRAM database file and it’s about 57MB for Xiaomi Redmi Note 4.

5. After selecting this file, the NVRAM file should be written to the phone in a matter of seconds. A success message at the bottom of the window should indicate this.

6. After this, key in your IMEI number in the space provided for SIM 1. You will only be able to write 14 digits, the 15th will automatically appear in the CheckSum text box. Click Download To Flash to write the IMEI to your phone. Note that you must use a valid IMEI. If you can’t get the original IMEI from your phone package box, you may need to use of the available IMEI generating apps.

Select SIM 2 and perform this same step. After you’ve successfully written the IMEI, you can now close this Window. Hit the disconnect button on the main program UI. You can now disconnect your phone and boot normally.

Your device should now be able to detect SIM card and your baseband version should appear in settings. This worked perfectly on my Xiaomi Redmi Note 4 (3GB, 64GB, Helio X20).