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[GUIDE] [HOW TO] Fix VS986 dropping down to 3G/H+ from 4G LTE

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By motorhead_biker, Member on 16th December 2015, 05:45 PM
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I've been working on a fix since a long time now. If you are in SD community then you prolly know me. Anyway I was able to fix this on two of my phones and it's working fine. I tested for 12 hours now. I'll also tell you in the end what problems I'm seeing. I'm also working on a fix for that.

I noticed that a service is started when the fallback happens but if I kill that service the network also dies. But if you follow the below method it safely starts a new service which kills the one that's responsible for killing the 4G/LTE

1. Upgrade your phone to 13B firmware
2. Root 13B
3. Now download Shortcut Master lite app from play store.
4. Now add these shortcuts to your favorites in the "Shortcut Master lite app". You can search for "LTE" and click on search button
LTEBandSelection
LTETestMain
LTE System Selection
CDMAPreference
5. Now click on "LTEBandSelection" and enable all the bands
6. Save and reboot
7. You now need to enable your data and turn off your wifi. Make sure your phone is in Global mode (in settings >> Mobile networks >> System select)
8. After your phone is rebooted open "Shortcut Master lite" app.
9. Now tap on LTETestMain
10. Select Click on CDMA preference.
Now choose Band preference and select "any"
P_REV_Preference ---> "MOB_P_REV 3
This is important.. EVDO Revision --> Rev A
11. "LTE Connect w/o IMS PDN" must be checked
12. Now go back to your main menu in shortcut master lit app
13. This step is very important. Changing the timeout is important. Tap on LTE System Selection
Except "Scan duration" add a couple zeros to all the other timers. For eg: T_mpsr timer (Min) is 200
The fallback timer will reset itself after reboot. But don't worry the configuration is already updated with the new value. For some reasons the shortcut master lite app is not picking it up.
14. Now finally click on "CDMA preference" in the main menu and make sure it has the value you set in Step 10
At step 10 or 13 your network should go away and your phone should complain about "no network". That's fine. just ignore the message.

Now finally reboot your phone. That's it. You should now have 4G LTE and it won't fallback to 3G or H+

The only problem is when I'm on a call my 4G LTE is dropped to 3G/H+. But after I hang up it goes back to 4G LTE after 12 seconds. I don't know if it's an expected behavior. But I'm trying to see if there is a fix for that.

I tested this with Tmobile. Make sure your APN settings are correct.
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16th December 2015, 06:05 PM |#2  
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Not working for me on Cricket (AT&T). Still will always go back to H+, 4G LTE only works when I select CDMA.
16th December 2015, 06:08 PM |#3  
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Quote:
Originally Posted by konradsa

Not working for me on Cricket (AT&T). Still will always go back to H+, 4G LTE only works when I select CDMA.

I tried it on my two phones (Both tmobile). My friend just tried it on his phone. It worked for him too.
16th December 2015, 06:09 PM |#4  
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Quote:
Originally Posted by motorhead_biker

I tried it on my two phones (Both tmobile). My friend just tried it on his phone. It worked for him too.

That's great! I hope we can figure out also what we need to do to get it to work for AT&T, I am sure it's probably just some small tweaks required.
16th December 2015, 06:13 PM |#5  
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Quote:
Originally Posted by konradsa

That's great! I hope we can figure out also what we need to do to get it to work for AT&T, I am sure it's probably just some small tweaks required.


I will try it with my roomies att sim tonight. He has a nano sim, I need to find a sim adapter.
16th December 2015, 07:03 PM |#6  
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Awesome, thank you! worked for me T-mobile.
it initially didn't work but I had to turn data off then on.
It also cycles me to 2g speed for a few seconds sometimes but that may be due to poor signal in building.
16th December 2015, 07:27 PM |#7  
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Quote:
Originally Posted by pwtzz

Awesome, thank you! worked for me T-mobile.
it initially didn't work but I had to turn data off then on.
It also cycles me to 2g speed for a few seconds sometimes but that may be due to poor signal in building.

Yeah It's due to the poor signal. I got that too. You can check your signal strength using LTE discover app.

But overall it's working fine for Tmobile. I'm gonna try and fix ATT tonight.
16th December 2015, 09:23 PM |#8  
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Is 13B the main thing in the solution? I've changed these settings before on 11A and wasn't fixed. I tried these numbers on 11A and still don't work.

Also, unless a phone supports VOLTE, it'll fall back to 3G/H for calls.
16th December 2015, 09:46 PM |#9  
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Quote:
Originally Posted by eigen

Is 13B the main thing in the solution? I've changed these settings before on 11A and wasn't fixed. I tried these numbers on 11A and still don't work.

Also, unless a phone supports VOLTE, it'll fall back to 3G/H for calls.

I tried in 11A and it didn't work for me. So I guess it needs 13B.
17th December 2015, 02:02 PM |#10  
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So I tried various combinations last night for AT&T/Cricket, but I was not able to get it to work. No matter what I tried, when I had 4G LTE, voice wouldn't work and whenever voice worked, I was back to H+.

If others are reporting that T-Mobile works reliably on 4G and nobody can figure out how to make this work for AT&T, I guess it's time to switch to T-Mobile.
17th December 2015, 02:30 PM |#11  
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Quote:
Originally Posted by konradsa

So I tried various combinations last night for AT&T/Cricket, but I was not able to get it to work. No matter what I tried, when I had 4G LTE, voice wouldn't work and whenever voice worked, I was back to H+.

If others are reporting that T-Mobile works reliably on 4G and nobody can figure out how to make this work for AT&T, I guess it's time to switch to T-Mobile.

No. Hold on. I have a solution for ATT too. I tried something last night. Actually while I was working on a solution for ATT I found that we don't even have to go through the steps I mentioned in my OP to solve the problem. It boils down to invoking a service and killing a native VZW service.

The ATT solution I have works but in low signal area 4G fades and it doesn't fallback to 3G or H+. I had to recycle data to get 3G or H+.
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