Install Android 5.1 Lollipop on Sprint Galaxy S3 with CM12.1 Custom ROM

by Alex · April 7, 2015

As I have already told you, CM 12.1 has been released for your Sprint Samsung Galaxy S3 which means that you can now update your phone to latest Android 5.1 Lollipop OS. The ROM might not be an official Android release provided by Sprint for your S3, but it is still the best way in which you can update your S3 to Lollipop OS. So, if you want to learn how to safely flash CM12.1 on your Sprint SGS3, read all the guidelines from below and in the end complete the following steps.

The first thing you need to know is that the CM 12.1 Android 5.1 Lollipop OS is not released by CyanogenMod. The CM team is currently providing Nightlies built of CM12, so the CM12.1 platform is developed by third party devs – those of xda-developers. Thus, you will complete an unofficial update operation since the present firmware isn’t also made available by Sprint. Because of that the warranty of your Galaxy S3 will get void if you decide to apply the lines from below. So, be careful when applying this tutorial and try not to mess things up – you can brick your phone if you don’t apply things as showed below (if something bad happens, don’t panic and just try to troubleshoot your SGS3).

You can install CM 12.1 on your Sprint Galaxy S3 only if your phone is rooted. An unlocked system is not an option as the Android 5.1 ROM must modify, customize and optimize in built features that are already running on your phone. After ensuring root access you have to apply a custom recovery image, such as CWM or TWRP recovery because the update package comes in form of a .zip file.

Do note that all these operations are unofficial, so it shouldn’t be related with Sprint, Samsung or with Google. Thus, you will tweak your Android device which means that you will no longer enjoy a pure Android experience – the Lollipop update is installed with a custom UI along with dedicated features and apps that cannot be found on the default Android system (for example, TouchWiz is not included on the CM 12.1 ROM). Because of these aspects, completing this tutorial is recommended only for advanced users and not for newbies.

A backup operation must also be performed if you don’t want to lose something during the update process – a hard reset will be required or else the Lollipop software can’t run properly. Moreover, a Nandroid backup might be a good idea – you can save and restore (if CM12.1 will not run as expected) the current ROM that is featured on your Sprint Galaxy S3.

These are only few of the pre requisites that must be completed when a custom ROM is involved. Thus, you shouldn’t go any further without checking this dedicated tutorial. There you can learn everything about this update operation along with other important info, so don’t head straight towards the steps from below if you want to make things work.

How to Install Android 5.1 Lollipop on Sprint Galaxy S3 with CM12.1 Custom ROM Firmware

You have to navigate towards this page; from there download the CM 12.1 Lollipop firmware file and save the update on your desktop.
It is important not to unzip this file.
Optional: download Google Apps package from the same page as the update isn’t including Google Apps.
Connect your Sprint Galaxy S3 with your computer via USB cable and place the downloaded files on your phone’s SD card.
Up next, remove the USB cable and power off your device.
Reboot recovery mode on your phone.
Hard reset your S3 and also clear cache by using the recovery mode menu: select “wipe data factory reset”, “wipe cache partition” and “wipe dalvik cache”.
Then, go back to main menu of recovery and pick the Android 5.1 Lollipop OS: select “install zip from SD card” and “choose zip from SD card”.
So, flash the CM12.1 firmware file and when done, install Google Apps package by following the same procedure.
You can now go back to Android OS by choosing “reboot system now” from main menu of recovery.

Congratulation; you have successfully installed CM 12.1 Android 5.1 Lollipop OS on your Sprint Samsung Galaxy S3. Test the new ROM and do share your experience with other users who might want to use this step by step guide – use the comments field from below in that matter.