[Sprint Samsung Galaxy S 4 Android Development] autoprime:
Sprint Galaxy S IV SPH-L720 SIM Unlock Method

Background

Sprint's new world-roaming GSM locked phones do not use an "unlock code" like typical GSM devices. Instead they are unlocked OTA... and only when Sprint allows this. Sprint cannot be relied on as the only method of unlock for multiple reasons. Some people have been "unlocked" by Sprint yet international SIM still do not work. Others own this phone but aren't using it on Sprint. For these reasons, a manual SIM unlock is needed. This post will explain how to do just that.
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Requirements

1. A Sprint GS4 on the MDC or MDL baseband. MF9 baseband will NOT work with this method. Downgrade baseband(modem) to MDC via Odin or Heimdall with THIS FILE. Thank you sxtpdevelopers.com and Rwilco12 for the file/hosting. You can go back to the MF9 baseband/modem after the SIM unlock by flashing THIS .TAR.. thank you noobnl for that. If the modem downgrade/upgrade doesn't stick.. try powering off completely then booting into download mode.. instead of rebooting directly into download mode. Sometimes this helps. I promise it is possible to go from MF9 -> MDC -> MF9

2. Samsung USB Drivers. Most of you should already have these. You can grab them HERE.

3. Windows PC or a Windows virtual machine.
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Directions

Press the "Click to Show Content/Spoiler" button below to display unlock directions.

It should not matter what SIM card is in your phone while doing the unlock. I usually unlock while a GSM SIM is inserted.. but it should also work if no SIM is in.. or the Sprint SIM is in.

1. After confirming you are on MDC/MDL baseband.. set your phone to diag mode.

Stock: Open the phone app and enter dialer code ##3424# then select Qualcomm USB Setting and select the last option, DM + MDM + ADB and hit OK. BE SURE TO SET BACK TO MTP+ADB WHEN THIS IS ALL DONE.You may be asked your for SPC/MSL code prior to the menu opening. You can get this from Sprint or by doing the following... Open ##3282# menu and hit Edit. Enter 123456 and it Ok.. you will be told it is incorrect. Now open terminal emulator and type in "getprop ril.MSL" without the quotes and you should have your MSL.

AOSP: Connect phone to computer. Enable USB Debugging in the Developer options. Open command prompt/terminal.

Enter adb shell. Then type su hit enter.

Confirm # then type setprop sys.usb.config diag,acm,adb then hit enter. This mode disables itself after you reboot the phone.

2. Now that you are set to diag mode it is time to install the Sprint S4 Unlock Tool, download HERE. pw on unlock tool zip = meanngreen04

@meanngreen04 was awesome enough to package my unlock method into a 1-click app. Show him some thanks.

If you do not have .net 4.5 installed on your machine you will be prompted to install it.

Confirm your phone is set in diag mode.

Press the Unlock button in the tool. Wait for for it to reboot. All done. You are now unlocked!!

To confirm you are unlocked without having to leave the USA and using an international SIM card: on the stock rom you should be able to put ANY GSM SIM card into your phone, power up the phone and check device settings to see the ICCID displayed. Prior to unlock the ICCID would be displayed as unknown. You will also notice the "Invalid SIM" message finally gone. On AOSP roms the only way to confirm without leaving the USA would be to use a 3rd party SIM app to read the ICCID... and that will only work if the phone is set to GSM. Again, even though we can NOT use our GS4 on ATT/T-MO.. we can still use ATT/TMO SIM cards to test the unlock.

I have been trying to get AT&T and T-Mobile SIM cards to get a signal... but that is for another thread/project. No promises.

Didn't work?

Try again. Make sure everything is confirmed working every step of the way. From diag drivers being installed correctly.. to diag mode being set.. to confirming you are on MDC or MDL baseband. Remember this will not work on MF9 baseband.

Make sure "PDA" is selected in the initial ##3424# menu.... not CDMA Modem.

To confirm drivers are installed properly check Windows Device Manager. Under the "Ports(COM)" section you should see 2 Samsung serial ports listed. If you do not see these... drivers are not installed or phone is not set in diag mode properly.

Some members have reported setting "DM over UART" in the *#9090# menu. This is something I've personally never had to do. The default setting with my phone is "DM/DUN over HSIC"

Last but not least... have you tried turning if off and on again?

That should cover all issues. Outside of those... USB cable could be bad... Windows PC could be messed up... phone hardware could be bad.

Questions asking for help unlocking without posting screenshots of (1)Device Manager confirming 2 samsung serial ports...(2) ##3424# menu.. and (3)baseband settings will be ignored.

Donation Link if you want to say more than thanks.
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