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Install CM 10.1 M3 Android 4.2.2 JB ROM for the T-Mobile Samsung Galaxy S3

Samsung Galaxy S3 T-Mobile variant is now ready to receive the CM 10.1 M3 Snapshot build. Use this post and you’ll learn how to install one of the best Android 4.2.2 Jelly Bean-based custom operating systems.

The CM 10.1 M3 ROM is a more stable release than the Nightlies, and if you’re a fan of CyanogenMod’s team, then this new ROM will be your best choice. However, if you’ve never used a CM-based ROM, then you should still give this one a try as I’m sure that you’ll enjoy using an AOSP Android 4.2.2 Jelly Bean. In order to make sure that you successfully flash the new ROM, you will have to read the preparation guide listed below:

  • Use this tutorial only with the Samsung Galaxy S3 T-Mobile variant. Don’t try to flash this custom ROM on any other Android device.
  • The T-MO SGS3 has to be rooted and the CWM or TWRP Recovery installed on it. Without these you cannot flash the new custom ROM.
  • Use the custom Recovery mode to create a full NANDROID backup of the ROM that is currently installed on your smartphone.
  • You will have to ‘factory reset’ your device before installing the new ROM. This means that you will lose installed apps and other data stored on your device’s System partition. The internal and / or external sdcards will not be affected by this installation.  NOTE: If your phone is already running a previous build of CM 10.1 then you can skip the ‘factory reset’ step.
  • Backup SMS, Call logs and APN Internet Settings using some of these tools: SMS backup & restore | Call Logs backup & restore | APN Settings Backup & Restore. Root access will be asked by some of these tools.
  • Sync your Contacts data with your Gmail account using this guide here. After the install is complete you will have to sync the data once again, so that all the saved phone numbers will be restored to your phone.
  • This is a guide for advanced Android users and you shouldn’t use it in case you don’t know what you’re doing. Make sure to read entire post before updating your smartphone.
  • Note that we cannot be held responsible in case you lose data or you brick your smartphone in the process. Don’t skip any steps that I have listed in the tutorial.
  • If you hit any roadblocks then you should ask for extra help in comments and we will try to come up with solutions for you. This is a guide that should be completed in under 5 minutes.
  • Remember that it is extremely important that you create a full NANDROID backup of your current OS. Usually, some custom ROM might not install successfully no matter what you do, which means that you will have to restore your device to a working state. The easiest way to do that is to restore the ROM backup files using the CWM Recovery mode.

These were all the instructions that you had to go over before starting the updating process. Continue to the next part of this post now.

How to install CM 10.1 M3 Android 4.2.2 Jelly Bean for T-Mobile Samsung Galaxy S3:

  1. Download the CM 10.1 M3 zip from HERE. Save the file to your PC and don’t extract its contents.
  2. Download Gapps for Android 4.2.2 JB ROMs from HERE. This zip contains all Google-based apps that your device needs in order to offer you the best Android experience. Do not extracts the contents of this file.
  3. Next, connect the SGS3 TMO to your computer. Move both zip files onto its internal SDcard storage. After the files have been successfully copied, then you should disconnect the smartphone from your computer.
  4. Power off your phone now.
  5. Boot it into CWM or TWRP Recovery mode. Do it by pressing and holding Volume Up, Home and Power buttons. NOTE: we’ve used the CWM Recovery mode for this guide.
  6. Now, when you’re at the main menu of the custom Recovery mode, select ‘backup and restore’ option. Create a full NANDROID backup of your current ROM. It is highly recommended for you to create this backup.
  7. Select ‘wipe data/ factory reset’ option next. Confirm this action. NOTE: If your phone is already running on a previous build of CM 10.1 Nightly or M Snapshot build, then you can skip this step.
  8. Select ‘install zip from sdcard’, then ‘choose zip from sdcard’. Find the CM 10.1 M3 zip file and confirm that you want to install it on your smartphone.
  9. Select ‘choose zip from sdcard’ again after the ROM has been installed successfully. This time you will need to find the Gapps zip and confirm its installation.
  10. After both files have been successfully flashed you should return to the main Recovery menu. Select ‘reboot system now’ and wait until your device boots into normal mode.
  11. The CM 10.1 M3 first boot process will take 5 minutes to complete loading all files. Enter your Google Account details when the Welcome screen appears and that’s the last installation step you had to take in order to flash a new ROM for your T-Mobile Galaxy S3.

If the smartphone doesn’t complete the first boot after 10 minutes, then you should power it off by removing its battery. After 5 seconds, re-insert the battery and then repeat the entire tutorial starting with step 5. This time you shouldn’t skip the actions listed under step 7.

I hope that you managed to flash the new OS. If you don’t like the CM 10.1 M3 custom ROM then you can easily restore it to its previous OS using the NANDROID backup file, the one created in step 6. If you have any other questions, leave them in comments.