UPDATE 8 : : PATCH for OREO is now available https://yadi.sk/d/bQhvMaY23REaXZ]here - credit to BlackzAfiqz
UPDATE 7 :
i gonna try to clean up this thread a bit and give a better instruction, since there are lot of changes since the initial post was created - all previous method and steps now moved to second post
So basically with latest situation, there r few steps you can try to unlock your band.
but before doing so, please READ few sidenotes/conclusion that we manage to gather so far :
1. This step was MADE for and TESTED on MARSHMALLOW, and MARSHMALLOW ONLY
2. The Rmt Storage Patch will still working up to an official N ROM version of 4.0.3
3. This step/trick
4. We only able to (partially) unlock bands THAT ARE AVAILABLE in one or another OP3/OP3T models. If the band is NEVER APPEAR on any of the available models, then currently it's NOT DOABLE. Example : Band 13 is nowhere to be found on any model of OP3, so there will be no support for B13, since there's not enough resources to do so
5. Up to today, there are some SUCCESS STORIES while using the method. Some of them are :
Myself, & @baskaflyfer of course - CN MODEL - B5 B8 UNLOCKED - B3+B7 CA UNLOCKED
@allluke - US MODEL - B3 UNLOCKED post #640
B3 working IMEI intact. Thank you so much
After following the guide, I was able to unlock band 3 in my US model OnePlus3 A3000. See attached images
I did all the steps. My IMEI is intact.
It takes some time for the signal to show up in Network Guru, so be patient.
In Network Guru->Band Locking->LTE, uncheck all the other LTE bands leaving only band 3 checked
Then go to RAT Locking and select LTE. Wait for the signal to show up.
If Network Guru goes to WCDMA, repeat last step.
I can confirm my LTE band 3 is working after flashing the new QCN, BUT after flashing the QCN you must reboot and then open QXDM and write 225 to NV item 1878, or else it won't work.
Here are my steps:
First I flashed this: (other/older QCN files posted by @otonieru will probably work too)
Then I rebooted, and flashed this: (Baskaflyfer's QCN)
Then I rebooted again, and flashed this: (Baskflyfer's fbrx file)
Then I rebooted, wrote 225 in NV item 1878 in QXDM, and finally got LTE signal on band 3 working here in Pakistan on my A3000US.
I managed to get it to work.
Now I have EU bands on my A3000CN
1. flash rmt_storage via twrp. (first page)
2. restore europe qcn. (first page)
3.restore A3003_eu from post #334 (third step)
4.run qxdm -> nv browser -> find id 1878 and change it to 237 (write).
5.reboot your phone.
1. Qualcomm USB DIAG Driver - Find it from post#2
2. QPST & QXDM - sorry but i can't redistribute it here, please look for it yourself
3. Main QCN for base, here : https://yadi.sk/d/E0y_4Ka63GNUdt
4. Extra QCN for fbrx_cal :
5. Rmt Storage Patch - find it from post #2 - For OOS 4.1.x download it from Here
6. Network Signal Guru App from PlayStore
Additional file for OP3T users :
1. OP3T EU QCN - Here
2. OP3T fbrx - Here
Now do the PRE-STEP,
1. Boot into TWRP
2. Flash the RMT Storage Patch according to your OS version, 4.1.x use Snowwolf version, bellow that, use Baskaflyfer version
Next, step is :
1. Opening DIAG - Assuming you got your phone rooted, run this command from ADB
setprop sys.usb.config diag,adb
3. Install the driver from requirement list number one, and you will have "HTC USB Modem" listed in your device manager (skip this step, if you already have your own qualcomm usb diag driver installed)-(remember to disable signature enforcement if you use WIN8/10)
4. Now fire up QPST and go to "Port" tab, and choose "Add New Port" ,
5. On "Serial/USB Port" tab, unchecked the option of "Show Serial & USB...bl bla bla" option, you will see your phone listed there as a "COM#" (# is a number depending on your PC) choose it, and click "OK"
6. Now choose "Start Clients" from the Menu tab above, and choose "Software Download"
7. Airplane Mode your Phone
8. Choose "Restore" Tab, and click browse for QCN file, and look for the QCN you have downloaded from requirement list Number 3 (if you need B3 on your US, use CN QCN, if you need B5 or B8 on your CN Model, use EU QCN. US QCN is still experimental)
9. Check "Allow phone/ESN mismatch"
10. Click "Start" and wait for the process to complete
11. After complete, wait 30 Seconds (for curing time), close QPST and reboot your phone
12. Once it fully boot, open back your CMD and re-run command from step number 1 to re-open your DIAG port
13. Use the "Software Download" function again, and restore the supporting QCN from requirement list Number 4 (choose one according to your needs)
14. Click "Start" and wait for the process to complete
15. After complete, wait 30 Seconds (for curing time), and reboot your phone
16. Once it fully boot, open back your CMD and re-run command from step number 1 to re-open your DIAG port, and make sure it detected on QPST
17. Now Open your "QXDM", choose options tab - "Communications", and choose the port according to your DIAG Port, and hit OK
18. Now choose "View" - "New" - "Common" - "NV Browser"
19. Go to NV ID 1878, and click "Read"
20. According to your needs, change the value. (If you need B3, B5, B8 on CN Model, use 237. If you need B3 on US Model, use 231 or 225)
21. Click "Write"
22. After complete, wait 30 Seconds (for curing time), close QXDM and reboot your phone
23. Run Network Signal Guru, choose "Clear Forcing" from the Tri-dot menu on top right
23. Continue with choosing "Band Locking" and choose only your new unlocked LTE Band. Hit OK, if warning about powercycle appear, just hit OK as well
24. Wait for a while until your phone picking up signal. To make it faster, you might want to lock your network mode to LTE ONLY through *#*#4636#*#* or through Network Signal Guru
That's it, if everything is well, you should have your new LTE BAND working now.