The CyanogenMod 10.1 M-build has been launched for the MetroPCS variant of Galaxy S3. You can learn how to install it using the instructions that I have listed in this post without risking any major damage for your device. Read all info and you should be able to flash the new custom Android 4.2.1 ROM in under 5 minutes.
The CM10.1 M1 ROM is a more stable variant of CM Nightlies builds and it is based on Android 4.2.1 Jelly Bean. It packs tons of customization options and features. Its main features are the improved Project Butter, Google Now, tweaked battery settings that should give you a better autonomy, a 360 Camera that resembles the one for the Nexus 4 AOSP ROM without the PhotoSphere function. However, you can browse the XDA forums and you will find guides on how to flash all the Android 4.2.1 AOSP vanilla ROM apps.
In order to install this new ROM successfully and at your first attempt, you will need to read the guidelines below. You will find info on how to backup data and other general instructions that should make the installation process a whole lot easier. Here’s what you need to know:
Use this guide only with the Metro PCS version of Samsung Galaxy S3. Do not attempt to install this custom ROM on any other device, as you will brick it. Don’t try to flash these files on the International or on the other US variants of SGS3.
The phone you’re about to update should be rooted and running a custom Recovery image. The Recovery mode should be used to create a full backup of your current ROM so that you’ll have a restore point for your device, in case something goes wrong during or after the installation.
The custom Recovery mode will be what you’ll use to flash the new CM 10.1 M1 ROM and we’ve used the CWM Recovery. You can also use the TWRP Recovery.
Charge the phone’s battery so that the device won’t power off while you’re flashing the new custom ROM on your SGS3 MetroPCS device.
We cannot be blamed for any data loss nor in case you brick the smartphone. Make sure that you read the entire post and you begin installing the new ROM only when you’re sure that you can complete it without losing data.
Use the comments section in case you need any extra help with installing the new ROM.
NOTE: If your device is already running a CM 10.1 ROM then you won’t be forced to factory reset it and, that means, that you can flash the new ROM right over the previous one. Check the info under Settings> About Phone and you’ll find the ROM version.
These were all the guidelines you had to go over before beginning to install the new ROM on your device.
How to install CM 10.1 M1 custom ROM on your MetroPCS Samsung Galaxy S3:
Download the custom ROM from HERE. Don’t extract its contents.
Download the Gapps for CM10.1 from HERE. You have to flash the Google Apps zip after you install the ROM, as it will add all the tools you need in order to benefit from the best Android experience.
Connect your SGS3 to your PC and copy the downloaded files to your phone’s internal SD card. When this process is complete you can disconnect the device from PC and then move on to the next step.
Power off your Galaxy S3 MetroPCS and then boot it into CWM recovery mode. Do it by pressing simultaneously the Volume Up, Home and Power buttons. When the custom recovery selection menu appears you can release the buttons.
If you don’t have a backup of your current ROM, then you will have to select ‘backup and restore’ option and create one. Users who already made that can skip this step.
Select ‘wipe data/ factory reset’ option and confirm.
Next, select ‘install zip from sdcard’ and then ‘choose zip from SDcard’. Browse for the CM10.1 M1 custom ROM zip and confirm that you want to install it.
When the custom ROM installs you will have to select ‘choose zip from sdcard’ once again. Find the Gapps zip and install it.
Return to the main Recovery screen when both files are installed with success.
Select ‘reboot system now’and confirm that you want to install it. Don’t press any other buttons and wait at least 5 minutes for the first boot process of CyanogenMod 10.1 M1 ROM to complete.
Enter the Google Account credentials when the ROM installs and then you can start using again your device just like you did before.
Customize your home screens and then test all the other new functions that were installed with the ROM.
These were all the steps that you had to take in order to make sure that the device will be updated with CM10.1 M1 build.
NOTE: if the first boot process takes more than 10 minutes to load or the device entered a boot loop, then you will have to remove the battery. Re-insert the battery after 5 seconds and then repeat the entire tutorial starting with step 4. Eventually you will be able to flash the new custom ROM without any further problems. If you still have problems installing it then you should ask for extra help in comments.
Also, if you don’t like how this new CM10.1 M1 ROM runs on your MetroPCS Galaxy S3, then you should use the CWM Recovery and restore the previous ROM using the ‘backup and restore’ option.