This is a second hand phone (originally on T-Mobile but now on MetroPCS) and is running the 30e build. Every time I switch it to GSM/WCDMA/LTE auto it will switch back on its own after coming off of wifi, rebooting, going to airplane mode, etc. Also, the wifi and data signals seem to fluctuate a lot even when standing still. On a recommendation I tried to switch to the 30d modem by downloading the file and installing it via the LG SW but was not able to choose the build to install (it just re-installed the 30e build). How can I force the 30d build to install and will it help me out? This is my last ditch effort before getting a new phone. I also tried the backdoor method of locking in LTE but it still cycles back to GSM.
Does it gives any random reboots????
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Every time I change my network mode to GSM/WCDMA/LTE (Auto) it goes back to GSM/WCDMA (Auto) after an hour or two. I can get LTE in my area and I do after changing the network mode setting manually, but after an hour or two my phone goes back to GSM/WCDMA and I loose LTE. I've tried going into the test menu and choosing my preferred network mode but it won't stay. My build.prop file has not been edited. I don't have the LTEconfigs.apk to delete.
Any ideas on what to do?
edit: I restored system partition from a backup. I'm fine now.
Have you at any point downgraded to KK from LP, then upgraded again back to LP? Because the same thing happened to me after downgrading, and then upgrading again.
redduc900 said:
Have you at any point downgraded to KK from LP, then upgraded again back to LP? Because the same thing happened to me after downgrading, and then upgrading again.
Click to expand...
Click to collapse
No, I never downgraded. I went from 10m to 10r to 20b to 20e, each time doing a complete system flash.
i have the exactly same problem except i am currently on 20g. I even reflashed the stock rom again and it still returns to GSM/WCDMA after reboot or idling for 1-2 hours. I changed the setting under the hidden menu as well and still didn't work.
any help is greatly appreciated.
This is a baffling problem. I have heard that both the cause and the cure is flashing back to KK and then back to LP. Among a multitude of other solutions with no real common thread. Having said that the one that makes the most sense is restoring your EFS backup, if you have one. For me I didn't have one.
Here is my experience, I wish I could say what was the real fix.
Started out at 10r and flashed CM12 as soon as I got the phone last Jan. About 6 months ago I had the common prob of the exclamation mark on my signal and no data. Used the LTE toggle to fix and lived like that for 6 months. Back in the fall I decided to go back to stock to see if it would fix. Flashed a stock zip of 20e. At 1st this was a disaster, I had no data and incidentally no APN. Oh by the way I have a TMO GS on at&t. Even after creating an APN no luck. I happened to have a live TMO SIM so I did a factory reset with the TMO SIM installed during 1st boot. This SIM is a prepaid w/o data, but it did attach to LTE. I then created an at&t APN swapped SIMs and LTE data worked. But now I had the problem of LTE not sticking. Usually dropped after a power cycle or going off WiFi, the later was not 100% reproducible, the former was. From a data standpoint I was better off as I no longer got the exclamation mark and no data. But OMG stock LG sux!
So along comes CM13. I see one guy that still had to do the LTE toggle, I figure not worth jumping in. But couldn't resit the pull of sticky Marshmallow and CM nighties. So I rooted and installed CM13. Amazingly I no longer have any data or LTE issues. Again, I wish I could give a clear path to fix. But maybe others can pull from my experience.
Good luck and if you get it working back up your EFS! Can be easily done via TWRP.
I flashed the firmware for COI5 manually via odin and ever since then I cannot connect to LTE. Furthermore, I can barely connect to any signal. The bars show up, but it often takes a while for the 4G icon to show up. When it does, I am still not able to place a call, with Wi-Fi calling being the only hope I have to do so, but calls placed to me that way go straight to voicemail, so I have to call out from my phone.
Note: Knox is tripped, as I was rooted. I am also in an area where I alway get full bars of LTE, so location is not the issue.
Troubleshooting steps I have tried:
Reflashing COI5 firmware via odin.
Adding the LTE APN for T-Mobile.
Using Smart Switch to do emergency recovery.
Flashing BOH6 firmware (did not work as I don't believe you can downgrade firmware, was worth a shot anyways).
Flashing different custom ROMs (all repeated the same problem, which is how I narrowed it down to having to do with the firmware).
I am currently running completely stock at the moment. If anybody has any suggestions on what I should try next or how I can fix this, I would greatly appreciate it.
Hi,
i'm currently running the latest CM13 and have a problem with the Preferred network type. It stays on "LTE (recommended)" and i can't change it to 3G or 2G. In Phone information (*#*#4636#*#*) it stays on "GSM only" and won't change to anything.
When i go back to LG's Stock 6.0 all changes work. With previous versions of CM13 (first 5 versions i think) it works also.
Does anyone have any idea?
Chipstepper said:
Hi,
i'm currently running the latest CM13 and have a problem with the Preferred network type. It stays on "LTE (recommended)" and i can't change it to 3G or 2G. In Phone information (*#*#4636#*#*) it stays on "GSM only" and won't change to anything.
When i go back to LG's Stock 6.0 all changes work. With previous versions of CM13 (first 5 versions i think) it works also.
Does anyone have any idea?
Click to expand...
Click to collapse
I have the same issue on my LG G4 h815. I cleanly flashed the latest nightly of CM13 (cm-13.0-20160102-NIGHTLY-h815.zip), after first upgrading to the stock 20A image and installed TWRP. I flashed CM13 using TWRP. Then I flashed nano gapps. H+ is the fastest cell tech here, and my phone just can't use the cell network (it seems to connect, but never shows H+ and no data bits are routed). And when I went into the menu to select 3G as the preferred network, it won't let me change it from LTE. It clicks when I choose 3G and 2G, but the selection stays on LTE. When I go into the special menu for radio options, same thing, I can't select a different network mode (it simply stays on the current selection). Wifi works just fine, but cell phone use doesn't work -- no calls, no data. I also upgraded to the next nightly, but it didn't make any difference in behavior.
@Chipstepper Can you tell me which CM13 image worked? I'm going to try cm-13.0-20151125-NIGHTLY-h815.zip ..
Same Problem here on my Moto X 2014. I tried every CM13 nightly between Christmas and early January. I was never able to change the Radiobutton in Preferred Networks and connection in phone information was always GSM only. I also tried a clean flash of the cm-13.0-20160108 nightly, still the same problem.
Now I switched back to my CM12.1 backup where it's working.
Can somebody name a nightly where it's confirmed working?
So the problem I'm having with my G3 is that the Network either drops and comes back repeatedly or completely drops and does not return. This only happens on 4G. When I go into network settings and change network mode to 3G it works fine and I get a constant signal all the time.
I have been using Fulmics ROM and I thought maybe that was the issue. But it wasn't.
I tried 3 different sims from three different carriers (Three, EE, O2) on several stock firmwares. (20N, 21C, 30A, 30F).
Each scenario is the same; network drops when phone is on 4G network mode, but its fine on 3G mode.
However, I have noticed that if I leave Wifi OFF allowing 4G data to connect first, then its fine. I can even turn Wifi ON again and the network is stable. I can even turn Wifi and Data OFF and the network is still stable.
But, if I toggle aeroplane mode, where Wifi connects first or where Wifi and Data is turned OFF; I am back to the network dropping.
Also, I live in London UK so there should not be any signal issues. Can anyone tell me why this is happening. I doubt it's software issue as I've tried several firmwares.
Any help is appreciated.
Mate I'm afraid there is a high possibility it's the Fulmics ROM.. I'm still trying to read up on the issue myslef, there's a ton of reports in the Fulmics thread and around.

I'm using an UK bought LG G3 as well (from Three) and started experiencing similiar issues after I flashed Fulmics. Even tried rolling back to 4.4.2 using a .tot file but didn't really help me.
Still scouring all around trying to find how to fix the issue..
engmia said:
Mate I'm afraid there is a high possibility it's the Fulmics ROM.. I'm still trying to read up on the issue myslef, there's a ton of reports in the Fulmics thread and around.

I'm using an UK bought LG G3 as well (from Three) and started experiencing similiar issues after I flashed Fulmics. Even tried rolling back to 4.4.2 using a .tot file but didn't really help me.
Still scouring all around trying to find how to fix the issue..
Click to expand...
Click to collapse
Hmmm looking back now this issue did start when I first installed fulmics 3.5. But shouldn't everything revert back to stock when you reinstall stock firmware.
thufz9585 said:
Hmmm looking back now this issue did start when I first installed fulmics 3.5. But shouldn't everything revert back to stock when you reinstall stock firmware.
Click to expand...
Click to collapse
That's what I thought but I guess it's a little bit more tricky.
Anyways I think I managed to restore some kind of stability in the signal, still unsure about the process though. Seems that different stuff are working for different people. In a few days I hope to have some information to give you how to fix it.
In the meantime try checking the Fulmics thread for ideas and suggestions (that's where I start off from).
engmia said:
That's what I thought but I guess it's a little bit more tricky.
Anyways I think I managed to restore some kind of stability in the signal, still unsure about the process though. Seems that different stuff are working for different people. In a few days I hope to have some information to give you how to fix it.
In the meantime try checking the Fulmics thread for ideas and suggestions (that's where I start off from).
Click to expand...
Click to collapse
Yeah let me know when you find a fix. Really appreciate the help.
One thing that is sort of a temporary fix for me, works on Three, EE and O2 (only ones i tried), is connecting Data first when on 4G mode.
So if I toggle airplane mode and if Wifi connects first then the network drops or keeps refreshing.
But, if I leave Wifi OFF and Data establishes a connection; the network is stable and I can then turn Wifi On again and the network will remain stable.
I just have to make sure the network does not lose connection (i.e. tunnel or airplane mode), and if it does ensure Data connects first.
Also, another thing. After I reinstalled Fulmic 5.3 it seems 4G mode is sort of stable. As in when on 4G mode instead of dropping the network it connects via 3G automatically. But this only happens with Three.
thufz9585 said:
Yeah let me know when you find a fix. Really appreciate the help.
One thing that is sort of a temporary fix for me, works on Three, EE and O2 (only ones i tried), is connecting Data first when on 4G mode.
So if I toggle airplane mode and if Wifi connects first then the network drops or keeps refreshing.
But, if I leave Wifi OFF and Data establishes a connection; the network is stable and I can then turn Wifi On again and the network will remain stable.
I just have to make sure the network does not lose connection (i.e. tunnel or airplane mode), and if it does ensure Data connects first.
Click to expand...
Click to collapse
Okay here is what worked for me - open this guide and download the Three specifiic Lollipop and Marshmallow .kdz files.
Flash the stock Marshmallow firmware first using the LG Flash Tool method. Your phone probably won't automatically get recognized since you're running Fulmics now so you'll need to change the COM port as described in post #
After that downgrade to stock Lollipop using the LGUP method. Personally I downloaded more updated (I think, not sure) files from here.
Then I proceeded to re-root and clean install Fulmics 5.1 and the 5.2 and 5.3 OTA updates from recovery. Booted and network works without drops now with 4G connectivity.
thufz9585 said:
Also, another thing. After I reinstalled Fulmic 5.3 it seems 4G mode is sort of stable. As in when on 4G mode instead of dropping the network it connects via 3G automatically. But this only happens with Three.
Click to expand...
Click to collapse
I changed my carrier and got an automatic SMS with configuration for my phone and instructions to save it. I should've known something was fishy when I recieved the "congratulations for setting up" message even before I recieved the actual settings. Anyways 4G was running fine on my new carrier with 32 mbps speed which is okay, much better compared to the same carrier 3G network, however I only had 3 bars of connection so I gussed what the heck, I should save that configuration after all, it might make things better. What a bloody mistake. I lost 4G connectivity and my phone refused to connect to the 4G network, only 3G (just as you describe).
What worked for me in this scenario was wiping the cache and dalvik (not really sure this step is even necessary to be honest, but I was headed for a full rom re-wipe anyway and decided to try with this first), going into the hidden menu and choosing LTE only connectivity (Fulmics Tweaks -> Hidden Menu [or the hidden code for the phone app if you decided to stay on stock, which I dont have] -> Modem Protocol -> RAT Selection -> LTE only. At this step my phone got to the usual 3 to 4 bars of connectiviy but was displaying "Emergency mode only" and no data at all. I proceeded to Settings -> Networks -> More -> Mobile Networks -> Access point names -> Reset to default from the menu. If network mode doesn't change back to GSM/WCDMA/LTE auto automatically, change it back manually. At this point I had restored back my 4G connection and everything is working normally (30-32 mbps connection stationary in my house through a wifi hotspot next to my laptop).
Good luck, I would follow the steps as described just in case. I tried many reflashes before that should've worked but didn't for me. However different things work for different people, hope this works for you and please report back
engmia said:
Okay here is what worked for me - open this guide and download the Three specifiic Lollipop and Marshmallow .kdz files.
Flash the stock Marshmallow firmware first using the LG Flash Tool method. Your phone probably won't automatically get recognized since you're running Fulmics now so you'll need to change the COM port as described in post #
After that downgrade to stock Lollipop using the LGUP method. Personally I downloaded more updated (I think, not sure) files from here.
Then I proceeded to re-root and clean install Fulmics 5.1 and the 5.2 and 5.3 OTA updates from recovery. Booted and network works without drops now with 4G connectivity.
Click to expand...
Click to collapse
I'd like to thank you so much for this information! I was having signal drop issue after installing Fulmics ROM. Tried to flash stock ROM but no success. After doing the downgrade via LGUP method to LP my phone is getting full signal again (at least I didn't notice any drop until now).
Thank you!
waltertakashi said:
I'd like to thank you so much for this information! I was having signal drop issue after installing Fulmics ROM. Tried to flash stock ROM but no success. After doing the downgrade via LGUP method to LP my phone is getting full signal again (at least I didn't notice any drop until now).
Thank you!
Click to expand...
Click to collapse
Glad I could be of help!
engmia said:
Okay here is what worked for me - open this guide and download the Three specifiic Lollipop and Marshmallow .kdz files.
Flash the stock Marshmallow firmware first using the LG Flash Tool method. Your phone probably won't automatically get recognized since you're running Fulmics now so you'll need to change the COM port as described in post #
After that downgrade to stock Lollipop using the LGUP method. Personally I downloaded more updated (I think, not sure) files from here.
Then I proceeded to re-root and clean install Fulmics 5.1 and the 5.2 and 5.3 OTA updates from recovery. Booted and network works without drops now with 4G connectivity.
Click to expand...
Click to collapse
Sorry for the late reply.
I followed your instructions and unfortunately it didn't work. :crying:
I first tried with the D85520f you provided and then with an updated D85521C firmware. But nothing worked.
The temporary fix, which I found works, is to ensure 4G mobile data establishes a connection first before Wifi (turn Wifi OFF then ON after data established). Then there is no signal drop until I go through a tunnel or phone restarts (signal drops completely), which means again i have to ensure 4G mobile data establishes a connection before Wifi or else it'll go back to the constant signal dropping.
Guess I'll just stick with 3G at all times. I've spent too much time trying to correct this than actually finding enjoyment in using the phone.
Anyway really appreciate the time and effort you took to help with this annoying situation. :good::good::good:
thufz9585 said:
Sorry for the late reply.
I followed your instructions and unfortunately it didn't work. :crying:
I first tried with the D85520f you provided and then with an updated D85521C firmware. But nothing worked.
The temporary fix, which I found works, is to ensure 4G mobile data establishes a connection first before Wifi (turn Wifi OFF then ON after data established). Then there is no signal drop until I go through a tunnel or phone restarts (signal drops completely), which means again i have to ensure 4G mobile data establishes a connection before Wifi or else it'll go back to the constant signal dropping.
Guess I'll just stick with 3G at all times. I've spent too much time trying to correct this than actually finding enjoyment in using the phone.
Anyway really appreciate the time and effort you took to help with this annoying situation. :good::good::good:
Click to expand...
Click to collapse
Modem 21C should be your answer! Please try with that.
Is anyone still out there
engmia said:
Modem 21C should be your answer! Please try with that.
Click to expand...
Click to collapse
I flashed dummies and get dropped 4g data like this.
I have tot back to stock and didn't help... not Kdz
Haven't downgraded yet to LP yet.
On turborom now.
Can I just flash this modem? Have a link to the 21c modem?
Flash in twrp or send via LG flash?
I flashed the the newest firmware, then flashed the Pefume 2.51.617.32 rom, and now the cell portion will not work. It will pick up a signal if I reboot, or sometimes toggle airplane mode. It will show 4g, but then it just goes back to the line over the bars. The sim card works in a Verizon iPhone, but if I manually try to connect to Verizon I get your sim card doesn't support this network error.
I assume I don't need to reflash the modem since I do get a signal after a reboot for about 30 seconds, then it goes away. I also have tried a factory reset, network reset, and verified my imei was still on the phone. I got this phone used with s off and unlocked bootloader already. It was running stock Android for Verizon 7.0. Firware was 2.41 before I updated it to flash the newer rom.
Any suggestions?
zoenphlux said:
I flashed the the newest firmware, then flashed the Pefume 2.51.617.32 rom, and now the cell portion will not work. It will pick up a signal if I reboot, or sometimes toggle airplane mode. It will show 4g, but then it just goes back to the line over the bars. The sim card works in a Verizon iPhone, but if I manually try to connect to Verizon I get your sim card doesn't support this network error.
I assume I don't need to reflash the modem since I do get a signal after a reboot for about 30 seconds, then it goes away. I also have tried a factory reset, network reset, and verified my imei was still on the phone. I got this phone used with s off and unlocked bootloader already. It was running stock Android for Verizon 7.0. Firware was 2.41 before I updated it to flash the newer rom.
Any suggestions?
Click to expand...
Click to collapse
I reflashed the modem a couple times, and it is now working. However, wifi calling doesn't show as an option.
zoenphlux said:
I flashed the the newest firmware, then flashed the Pefume 2.51.617.32 rom, and now the cell portion will not work. It will pick up a signal if I reboot, or sometimes toggle airplane mode. It will show 4g, but then it just goes back to the line over the bars. The sim card works in a Verizon iPhone, but if I manually try to connect to Verizon I get your sim card doesn't support this network error.
I assume I don't need to reflash the modem since I do get a signal after a reboot for about 30 seconds, then it goes away. I also have tried a factory reset, network reset, and verified my imei was still on the phone. I got this phone used with s off and unlocked bootloader already. It was running stock Android for Verizon 7.0. Firware was 2.41 before I updated it to flash the newer rom.
Any suggestions?
Click to expand...
Click to collapse
Did it work before you flashed it?
Is the SIM locked to your iPhone?
Do you have a network update option? Does the network need time to recognize the new phone? (I haven't used CDMA in years, don't remember beyond it being a pain)
zoenphlux said:
I reflashed the modem a couple times, and it is now working. However, wifi calling doesn't show as an option.
Click to expand...
Click to collapse
There is a thread similar to this in the Verizon forums.
https://forum.xda-developers.com/verizon-htc-10/how-to/vzw-how-to-unlocked-model-vzw-t3376743/page40
Might not be so easy to get working. Since you're on the verizon network I would just convert it back to VZW software. The Oreo update is supposedly coming soon, and that way you wouldn't have to mess around flashing radios, etc.
I flashed all the way back to 1.85 Verizon RUU, and had to run the erase modem fastboot commands to get wifi calling back. I then flashed Twrp and the newest custom rom based on 2.617 and wifi calling is still in place! However, I lost my home button. I quickly figured out the firmware was still on 1.85 from the flash down to 1.85, so I flashed the newest firmware to match the rom and everything is back working.