Solve Problem With 4g/lte (sim1) Redmi Phones

[ils15]

ORIGINAL POST HERE
http://en.miui.com/thread-335643-1-1.html

Problem: phone does not connect to 4G (sim 1)
The phone has no 4G signal in two sim cards
the network is falling or not connect at 3G mode (H+)
Explaining the problem:
Some CHINESE vendors to distribute SHOP ROM, install a modified QCN (Chinese baseband)
The QCN is the phone's IMEI file that has data and other information related to RADIO.
what happens ...
This QCN is blocked 4G in main IMEI (not know pq not the secondary IMEI) for most non-Asian countries
For this reason, when configuring the unit to another location (eg, Brazil, Europe, etc) this block 4G / LTE networks access

IMPORTANT: DO AT YOUR SOLE RISK. The TUTORIAL INVOLVE ESSENTIAL FILES MANIPULATION FOR THE FUNCTIONING OF CELLULAR NETWORK. ANY ERRORS, MAY RESULT IN FAILED CONNECTION / NETWORK.
requirements:
bootloader Unlocked
Superuser
Rom miui (not tested with other variables)
Fastboot Files and ADB files: https://goo.gl/eJGlJR
Qualcoom Drivers: https://goo.gl/H1QZIw
Files for IMEI handling: https://goo.gl/ueKhWr


EDIT: If you expecting issues
try to flash this archive before make the tutorial
https://goo.gl/WV8U7p

put cellphone in fastboot, and this archive inside folder with fastboot
after it, excute CMD and use this command to flash

fastboot flash modem NON-HLOS.bin


Another advice: need to reboot more then 1 time
pay atention
1. Unzip the fastboot files
2- Unzip the drivers Qualcoom
3. Unzip the files of 4G Restore Folder
4 Install QPST and WriteDualIMEI programs (W + G_eMMC), located in the Restore4G folder
Now it is the part that manipulate cell
IMPORTANT: Write down BOTH the IMEI of your phone
for this open the dialer and enter * # 06 #
This is critical cause we will delete them in the process.
5. Connect the phone to your computer with the USB debugging connected
6. Open CMD in the fastboot folder by clicking the shift button + right mouse>>> Open command window from here

7- Activate the DIAG mode on your phone, so that it can recognize the phone as a communication port. To enable diag mode run the following commands:
adb shell
su
setprop sys.usb.config diag,adb

8. At this time, the phone must be recognized as follows:

9 Using QPST, back up your QCN file:

To do this, open the program and go to the Start tab Customers >>>>> >>>> Backup software download (THIS STEP IS CRITICAL BECAUSE SOME TROUBLE IF THE METHOD, ENOUGH TO REPAIR YOUR QCN)

10 after back up, run the following commands in fastboot:
adb shell
su
dd if=/dev/block/mmcblk0p13 of=/sdcard/modemst1
dd if=/dev/block/mmcblk0p14 of=/sdcard/modemst2
dd if=/dev/block/mmcblk0p16 of=/sdcard/fsg


dd if=/dev/zero of=/dev/block/mmcblk0p13
dd if=/dev/zero of=/dev/block/mmcblk0p14
dd if=/dev/zero of=/dev/block/mmcblk0p16
These three last will delete any information modem and radio, and restart the phone.
(IMPORTANT: the message of insufficient space can be skipped)
After restarting the device, the phone will not recognize the SIM (normal)
* Each time you restart, u need a cell in DIAG mode (step 7)
11- Open QPST >>> Start Customers >>>>> >>>> Restore software download
Choose 80DE5873_0.qcn file (this is the global QCN)
check the allowphone / FileMismatch
Ignore the error talking on the phone model, if it appears

12- restart the phone
13- The phone will be with global QCN, but with wrong IMEI.
To rewrite your IMEI, open WriteDualIMEI application (must be in diag mode):
Write the IMEI in the program and press start:

You receive a PASS
Restart the phone
Obs .: When performing the procedure, it may be that the cell "delay" rather to recognize 4G networks ... I do not know why that, but here I had to make the search a 2 times
after that, the network began to recognize automatically
IMPORTANT: ONLY TESTED ON RN3P (SNAPDRAGON)
do not know if rolls on other devices, due to the QCN model.


Please pass feedback and only if you do what you're doing CERTAINTY
thanks for @BharatG and @Archelot (from MIUI forum) and vkass from XDA forum