[LG G8 Guides, News, & Discussion] Wish39:
If you are running Android 12 or 13, follow this guide if PDC does not see your device.

I'm gonna keep the intro simple, been a longtime user here on XDA, and recently I found that my T-Mobile LG G8 only supported VoLTE and VoWifi on, you guessed it, T-Mobile! So I did some research, experimented with my G8 for a bit, and I now have a method that works and does not need root at all. Basically, what we are doing here is just loading carrier profiles into the phone's modem so that the phone is able to complete IMS registration and correctly provision VoLTE when you insert a SIM card from another carrier.

If you are trying this on a LG V60, please turn off USB debugging before attempting this as multiple V60 owners have had trouble properly installing the modem driver and only resolved the driver issue by turning it off. Also, please try the 90E5 driver if the 9091 driver does not work for you.

This method does not work on the Sprint G8, any other Sprint LG devices, the Korean G8 and any other Korean LG devices since there is no Field Test option in the HiddenMenu in those devices.

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DO THIS FIRST!!!!!: STEPS TO OBTAIN CARRIER MBN FILES FOR YOUR DEVICE

(MBN files for the G8/G8x/G8s provided in Step 11 of the main guide)

1. Download a KDZ for your device. Sites like lgrom.com or lg-firmwares.com have KDZ's available to download. If you have an AT&T LG device just download a KDZ for another variant of your phone. Ex: If you have the AT&T LG Velvet, just download the Canadian Velvet's KDZ. Same for the AT&T G8, G8x etc.

2. Download and install 7zip, and the linked/attached KDZ extractor tool.

3. Extract the KDZ tool zip file, then place your downloaded KDZ into the same folder as the KDZ tools.

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4. In the KDZ tools folder, find "OneKeyExtraction.bat" and double click on it.

5. When the CMD windows launches, press Y to start extracting the partitions from the KDZ.

6. Once it is finished, you should see a new folder in the KDZ tools folder that has the same name as the KDZ that you downloaded. Open up that folder.

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7. As you can see the tool extracted all of the partitions that are contained in the KDZ file. We will need to open up either the modem_a or modem_b partitions to grab the needed MBN files. Scroll down to find those partitions. Doesn't matter which one you choose.

8. Right click on whichever one you chose, hover over "7zip", then click "Open archive".

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9. 7zip will open up. The folders where the MBN's will be vary by device. Generally you should first look for a folder named "modem_pr", then once in it find the "mcfg_sw" folder. Here are some examples to help you find where the MBN files in your device's modem partition are. The files will be seperated into folders by region and carrier.

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10. Once you find the files, extract them to whichever folder you want to.

Now here are the steps to load the MBN's:

1. Download the latest QPST Tools from here. Only runs on Windows. No Linux, sorry.

2. Extract the zip file you downloaded and open QPST.2.7.496.1.exe to install the QPST tools.

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3. Once that is done, go to the Driver folder and open Qualcomm USB Driver V1.0.exe to install the drivers needed for the tool to communicate with your phone.

4. After that is done, there should be a QPST folder in your start menu. We'll come back to that later.

5. On your phone, go to the dialer and enter this code:

*#546368#*xxx# OR #*462633*#xxx# *xxx is the three numbers in your device's model code.

6. The HiddenMenu should pop up, choose Field Test, then LTE Data Test, and change the Tethering Mode from Android to QMICM. I recommend leaving your phone in this menu so that it is easier to switch back to the normal Android USB connection mode when you are done.

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7. Connect your phone to your computer, it should be detected as "Qualcomm HS-USB Modem 9091". In Device Manager it should show up under the Modems section.

8. Go to the QPST start menu folder and open the "PDC" application.

9. Go to the Device dropdown, there should be an item named "Qualcomm Wireless HS-USB Ethernet Adapter 9091". This is your phone, select it.

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10. This is what you should see. Notice how only the original carrier's (T-Mobile) modem profile is loaded into the phone's modem. Pretty lazy if you ask me.

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11. Now you will need some modem profiles to load into your phone! As a little starter pack, here are a few carrier modem profiles for US, Canadian and Korean carriers. Download them here (these are only for the G8/G8x/G8s! Will not work with other devices!!!!!!). I have extracted these from my phone's modem_a partition using QFIL Partition Manager with the LG SD855 firehose, and these are present in the modem_b partition as well. LG left all of these profiles inside the phone but only actually loads one of them into the modem on carrier models....

These profiles may also work on the G8x, V50, and G8s since those phones have the same SOC as the G8, and by extension the same modem chip.

12. Once you are ready, press the Load button and navigate to whichever carrier profile you want to add, I will load AT&T as an example. After going inside the folder for the carrier you want to load, there should be a file named "mcfg_sw.mbn". This is the profile. Don't bother adding any profile that has "row" in it's name, those usually don't give you support for VoLTE.

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13. When you are ready, click Open and your carrier profile will be loaded into your phone! You can go and add as many carriers as you want, I loaded all US and Korean, and some Canadian carrier profiles into my G8.

Do not load the same profile multiple times, this may cause issues with VoLTE and cell connectivity.

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14. When you are done, go back to the LTE Data Test menu and set the tethering mode back to Android. Your phone now has VoLTE support for the carriers that you loaded into it!

If you have another Qualcomm LG device, you can also follow this guide, you just need to enter the HiddenMenu dialer code specific to your device, and have carrier config files that are either specifically for your device, or from another phone that has the same chipset as your device* (*may or may not work).

Here's AT&T VoLTE working with a Tracfone AT&T sim card on my previously incompatible T-Mobile G8:

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Hope this guide has helped you guys!

If VoLTE is still not working for you, then give johndaniel's method a try!