[Sprint Galaxy S 5 General] fsantiago21:
Try following these instuctions

Hey Viper,

Thanks for the info you posted earlier. I was able to fully downgrade my modem on my L720T.

I also had the same problem you were facing, so I went to another forum and followed the instructions with a few more steps,

Mines is now working just fine after I followed these instructions.

Here you go:D

"3) I went to the dialer and typed *#0011# which brought me to the "service mode" Menu.

IF YOU HAVE TROUBLE GETTING THE HIDDEN MENU TO OPEN DO NOT FEAR! I had a ton of trouble at first. In some builds you need to activate an option by adding a line to your build.prop or changing the no flag in efs/hiddenmenu to ON. Google it, there is a ton of help out there.

4) Press the left menu softbutton (the menu button that lights up and vibrates when you touch it) then press the either the button “select” or “Key Input” and type the number 1 or 2 into the box, if nothing happens press menu and select the “back “ button then repeat. This app is sort of like a tin can radio, you can kind of tell that it’s working, but it doesn’t work well.

Depending on if you pressed 1 or 2 in the dialogue box it will take you into either an UMTS or CDMA menu. If you are in the umts menu, press the menu button and select back, this should then proceed to the next step.

5) Select CDMA, then 1.COMMON, press next page twice until you reach page three of COMMON and select 8.PREF MODE SET and select GSM_WCDMA_ONLY

6) Press menu and back until you are at the main menu and select [1]UMTS, then select [1]DEBUG SCREEN, then select [6]PHONE CONTROL, select [2]FAKE SECURITY CONTROL and make sure it is set to ON

7)Press menu and back and select [3] NAS CONTROL. We are going to check a few different settings in this menu so remember how to get here cause I don’t want to repeat myself.

[1] CIPHERING CONTROL = OFF

[2] INTEGRITY CONTROL =ON

[3] SIM CLASS CONTROL = UMTS

[4] REVISION CONTROL = DO NOT TOUCH

[5] RRC(HSPA) CONTROL = DO NOT TOUCH

[6] DUALMODE IMPROVEMENT CONTROL= DO NOT TOUCH

[7] NAS AVOID SECURITY CONTROL= OFF, 0

[8] BIP BLOCK = 1

8) Press menu and back twice, you should be on the PHONE CONTROL menu. Select [7] NETWORK CONTROL, select [1] GFC and make sure that it is set to [1]GSM/(E)GPRS/WCDMA REL8 .

9) Press menu and back and select [2] BAND SELECTION and select WCDMA/GSM ALL for both WCDMA and GSM band preferences. I selected the ALL choice for LTE as well even though I know it isn’t supported for TMOBILE.

10) Under the NETWORK CONTROL menu we just came from select [4] AQUISITION ORDER and change it to [3]UMTS_GSM

11) Press menu and back until you are in the PHONE CONTROL menu and select [5] SIMULATION , press the [2] SW WATCHDOG button 6(six) times and then the [3] HW WATCHDOG 6(six) times. Nothing will happen at all to let you know if you have done this correcctly but as soon as you finish the sixth press on HW WATCHDOG reboot the phone manually:manually:manually IMMEDIATELY . I’m not sure what this does or why this works but [MENTION=4988907]nicotheandroidguy[/MENTION] seems to have divined that this is the vital part of the process.

YOUR PHONE STILL WILL NOT HAVE DATA OR VOICE WHEN YOU REBOOT FROM THE WATCHDOG TAPS DO NOT PANIC!!!!!!!!!!! (hopefullly you have your towel with you)

12) WIFI that sonofa up and search for apn settings shortcut and build.prop editor in the Play Store.

Go into the build.prop editor and add the following two lines:

ril.sales_code=LOL

ro.csc.sales_code=LOL

REBOOT PHONE MANUALLY now.