Restore IMEI of Xiaomi MI4C Without Another Phone

Question

In short: I have a Xiaomi Mi4c that shows has an "unknown" IMEI when checked via the settings in the stable and developer versions of MIUI and Cyanogenmod 13.1. However, when viewed through EFS professional or NV RF Manager, the IMEI is read correctly. Not having a "valid" (or any?) IMEI means I have a 5" wifi tablet, rather than a phone, which is something I've been trying to fix.

The long version:

The problems started right after I flashed CM 13.1, and I couldn't detect my sim card. Thinking it was my ROM, I reflashed my stock ROM and when that didn't solve the problem, I quickly deduced that the missing/unknown IMEI was the problem.

I finally got NV RF Manager working, and read all of the NV values from my phone. After finding the IMEI related value, I followed the odd schema for rearranging my IMEI and filled the boxes out and clicked "Write NV." However, I only received an error that read "Parameter is write-protected and thus read only." The same results were achieved with EFS professional. (Again, this was on CM) Now, I reflashed the stock ROM, and tried again. After rebooting the phone, I was able to read the correct IMEI values from the phone using both EFS professinoal and NV RF Manager, but the phone still showed baseband and IMEI as "unknown." Dialing *#06# causes the numbers to disappear, but nothing else happens.

So far, this is what I've tried:

NV RF Manager

EFS Professional

MTK Droid Tools

SP Flash Tools (Did not work at all, only for MTK chipsets?)

Apps like XPOSED IMEI Changer (Results in nothing changing)

There are a few related questions, but none of them work for me.

How to restore IMEI and get back network functionality?

Might work, but I have been unable to find the "modem" or nvram files on my phone. I also don't have an "efs" folder on my phone (that I can find.)

Mi4i full partition corrupted. Unable to restore EFS partition

Isn't jiving with me. The thought of uploading mi4i (rather than mi4c) specific files after removing my only remanents of my efs files seems like a bad idea to me.

How to restore the IMEI number on the Samsung Galaxy S4 I9505?

Is ROM specific, and since it doesn't work on multiple ROMs, I've ruled it out as related.

Again I have a Xiaomi Mi4C, the 32GB/3GB version with the Qualcomm MSM8992 Snapdragon 808 chipset.

Any help at all would be greatly appreciated, I've hit a wall fixing this problem.

— BSL-5 | Sources

Answer

This is what worked for me. I've documented everything in a GitHub repository, and have included some of the information here. However, I will not be updating this information, and I cannot upload the supporting files, making the GitHub repository the go to resource for many reasons. With that said, here is the excerpt:

Download files

I've attached a few files:

mi4c.qcn: an IMEI backup from another phone

QPST: the program for uploading the IMEI backup

IMEI converter converts IMEI to hex

The IMEI converter is optional, but useful.

Root phone and enable USB debugging

Other people have already written this part up, and in the spirit of refactoring, I will link to them rather than repeating what they say.

Unlocking the Mi4c Bootloader without verification by Xiaomi

Root and install twrp recovery on Xiaomi mi4c

SuperSu install

Enable USB debugging

Setup other software

Here's a guide for how to install ADB and Fastboot.

You'll need a hex editor. Here's one, but there are many to choose from.

Enable diagnostics mode

Open up your command prompt and run

adb shell

su

setprop sys.usb.config diag

This enables the diagnostics mode on your phone, priming it for QPST

Check drivers

Go to "Device Manager" and check if your drivers are installed correctly. If they are not, try enabling unsigned drivers and reinstalling/updating the drivers for the phone.

Edit mi4c.qcn

Open up your hex editor and search for "08 5A 44 13 66 06 75 76 36"
Change this to your IMEI that you converted into hex with the IMEI converter attached.

Erase existing IMEI files

adb shell

su



dd if=/dev/block/mmcblk0p28 of=/sdcard/modemst1

dd if=/dev/block/mmcblk0p29 of=/sdcard/modemst2

dd if=/dev/block/mmcblk0p33 of=/sdcard/fsg



dd if=/dev/zero of=/dev/block/mmcblk0p28

dd if=/dev/zero of=/dev/block/mmcblk0p29

dd if=/dev/zero of=/dev/block/mmcblk0p33



reboot

This clears the way for the new files.

Repeat Enable diagnostics mode

Use QPST to update EFS

Install and run QPST. It should automatically detect your phone.

Click the "Start Clients" tab, then select Software Download

Select your modified qcn file and click start. It may reach 100% quickly, but it will still be working until the exit button is not greyed out.

Reboot phone

Celebrate! (Or retry if not successful, sometimes it takes a few tries to get it right)

Credit to http://www.miuitutorial.com/2016/10/imei-xiaomi-mi4c-kamu-hilang-jangan.html and Defforest@enMiuiForum