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Update AT&T Samsung Galaxy S3 I747 with Official CM10 M2 Jelly Bean ROM

The M2 release of CyanogenMod10 based on Jelly Bean happened several days ago and this is monthly update build ROM that you can learn how to install by using the instructions that I have listed in this tutorial.

This latest CM10 M2 custom ROM firmware for Android phones is running a modified Android 4.1.2 AOSP OS and now you can install it on your AT&T variant of Galaxy S3. It comes with numerous fixed bugs and other tweaks, improvements that will improve the overall performance of your phone. If you’re a fan of CyanogenMod releases then the CM10 Jelly Bean M2 ROM should be running on your device.

Before starting to apply the update you should read the preparation guide and learn how to properly configure your device and which tools you should use in order to backup your most important files. Note that you should read all the guidelines below and only when you’re sure that you know what you’re doing, you should move to the next part of this tutorial.

Here’s what you need to know before installing the CyanogenMod 10 M2 custom ROM on your AT&T Galaxy S3:

  • Check your phone’s model number by opening the Settings menu and then scrolling down to ‘About device’ option. If the I747 model version is listed then your Galaxy S3 is the AT&T one. Do not attempt to flash these files on any other phone’s.
  • The Galaxy S3 AT&T variant should be rooted and running a CWM Recovery image. Without these requirements being met, you won’t be able to flash the CM10 files.
  • Save a list of installed apps, SMS, Call Logs and the APN Internet Settings using the following Android tools: SMS backup & restore | Call Logs backup & restore | APN Settings Backup & Restore | AppBack for Android. Note that some of these tools will work only with rooted devices.
  • Use the CWM Recovery, ROM Manager or the ROM Toolbox to create a full backup of your currently installed ROM. This backup can be easily restored in case you don’t like the new CM10 release and you don’t want to use it. Also, the backup will come in handy in case something goes wrong in the process and the phone cannot boot successfully in normal mode.
  • Sync your Contacts with your Gmail account.
  • Enable USB Debugging option from your phone’s Android Development menu.
  • The CM10 M2 is not an official Samsung release, but a custom AOSP ROM created by the CyanogenMod team.
  • Remember to charge your phone’s battery so that it won’t power off while you’re installing the new custom ROM.
  • Note that we cannot be blamed in case your device gets bricked or in case you lose any important data files after installing the CM10 M2 build.
  • Read the entire tutorial and don’t skip any steps that I have listed in it. If you cannot complete the update, then you should tell us in comments and we will try to help you complete the update.

Now that you know all of the above, I think that you should move to the next part of this post and learn how to flash the custom firmware on your I747 device.

How to update the AT&T Galaxy S3 with Official CyanogenMod 10 M2 Android 4.1.2 custom ROM

  1. Download the CM10 M2 JB zip file from HERE. Make sure that you download the latest build. Save the file on your PC.
  2. Download the Gapps file for Jelly Bean from HERE. Do not download the other versions, just the one for Jelly Bean. Also, save the file on your PC.
  3. Next, connect your phone to your computer via USB cable. Move the files downloaded at steps 1 and 2 on your phone’s internal SD card. After the transfer is complete you should unplug the phone from PC.
  4. Power off the Galaxy S3 AT&T and then boot into CWM Recovery mode. It can be done by pressing ‘volume up’ + ‘home’ + ‘power’ buttons. Release the buttons when the screen powers ON.
  5. When you’re at the first screen of CWM Recovery, you should now select ‘wipe data/ factory reset’ option. Confirm. NOTE: In case your device is already running a CM10 firmware, then you might not need to apply this step. However, in case yours isn’t, then you should move to the next step only when the factory reset operation is complete.
  6. Now, select ‘install zip from sdcard’ and from the next screen select ‘choose zip from sdcard’. Find the CM10 M2 ROM zip and confirm that you want to install it.
  7. After the ROM is installed you need to select again ‘choose zip from sdcard’. Find the Gapps for Jelly Bean file and confirm its installation.
  8. Return to the main CWM Recovery screen when all files are installed. Select ‘reboot system now’.
  9. The AT&T Galaxy S3 device will now perform its first boot with this new ROM and it might take 5 minutes to complete the process.
  10. After the boot is complete, you will see the CM10 Jelly Bean 4.1.2 home screen and you should enter your Google Account details and take full control over your device.
  11. Test the custom ROM and tell us in comments if you find any bugs or errors.

NOTE: In case the update isn’t completed or the phone doesn’t boot after installation, then you should power off the device and keep it that way for 5 seconds. Boot again into CWM Recovery and then repeat the tutorial starting with step 4. Try to install again the update and make sure that you apply step 5 this time, but note that all installed apps, SMS and other files will be removed. The internal SD card contents won’t be removed.

If you have any extra questions or concerns, then you should tell us in comments.