Update Galaxy S2 GT-I9100 to Android 4.1.2 XWLSZ Official Firmware

Here is a tutorial on how to update Galaxy S2 GT-I9100 to Android 4.1.2 using this particular stock firmware: XWLSZ. Pay attention to all the steps and instructions in it and your upgrade will be successful!

There are some mighty fine features coming with the new firmware. To have all of them included on your Galaxy S2 I9100, you should use only this version; if your handset is not this model, you will brick it. If there’s a custom ROM on your device, this guide is still available for you to follow. If, however, you want to update the phone using KIES, you can; the KIES logo of this firmware is activated. But you will need to have an official ROM installed on the handset. The same should happen if you want to upgrade your device via OTA.

The new Jelly Bean firmware has been available for Ireland (O2) and Switzerland ever since October this year. When you’ve flashed the new firmware on your smartphone, the latter will come at you with these new features: sync and connect email updates, triple buffering all share, pop up play, extended Vsync timing, automatic adjustment for the size of widgets, mini apps, touch anticipation and free style widget, Google Now, a new keyboard, a fixed frame of 60 fps and group cast.

In case you’ve rooted your smartphone, the update will revoke the root access. The internal/external SD cards and the important data will not be affected, but the system partition will be deleted.Galaxy-S2-I9100


Now for requirements:

  • in case the phone’s battery levels are low, you need to fully charge the unit;
  • your notebook should only have Windows as an OS;
  • make a normal backup together with a full NANDroid one using this guide;
  • USB Debugging must be enabled on the Galaxy S2 GT-I9100;
  • the laptop’s and handset’s security software must be disabled while you upgrade your device;
  • after you locate USB drivers for the handset, we advise you to go to your laptop and download them there.


  1. The time has come to download, save and then extract, on the laptop, the Android 4.1.2 XWLSZ (download the Ireland O2 version from here and the Switzerland version from this place) and Odin from this page.
  2. Boot your handset in Download Mode for the next step by pressing and holding Volume Down, Home and Power at the same time and, as soon as the Android logo and a warning screen are displayed, you will know that you’ve reached the correct mode.
  3. So move on by opening the Odin on the laptop as an Administrator and then doing the following with the phone’s USB cord: connecting the device to the notebook and waiting until a connection is established.
  4. To know whether or not the latter has happened, the screen will display an “Added!!” message together with a yellow ID:COM box. If neither of them shows up, here is what you can do to make it happen: install the USB drivers on the notebook one more time or use another USB port.
  5. When the plugging has been accomplished at last, you should follow this bunch of instructions: tap PDA, opt for a file with CODE in the name, after which you should tap Phone, opt for a file with MODEM in the name, tap CSC, opt for a file that should have a CSC in its name, tap PIT and look around for a file with a .pit extension and choose it when you spot it.
  6. Then you can do this: check Auto Reboot, Re-partition and F. Reset Time boxes. Tap, when you’re done, the button called “Start”.
  7. The Jelly Bean 4.1.2 XWLSZ is going to be flashed on your Samsung I9100 after a couple of minutes, so you will have to wait for that to happen. Once the smartphone begins to restart and comes up with a “Pass” on the screen, you will know that the new firmware is part of your device now. Disconnect it from your notebook and see if you like it more than the previous ROM.

In case you actually don’t, you should know that the NANDroid backup file from before can be used to revoke the upgrade and restore the old ROM on your Galaxy S2 GT-I9100.

Please leave a comment in the section below if anything bad happens during the update or you want to ask us something.

Posted In How To - By Mihai Mateescu

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