Samsung Galaxy S III - International GT-I9300
This a short list of frequently asked questions with answers related to the Samsung Galaxy S III. It should serve as a starting point for gathering knowledge and finding solutions to many common problems. Please only post in this thread with feedback on how to improve this document and refrain from posting "Thank you" type responses. If you have additional questions or require more help, try to find an existing thread or create your own. Do not use this as a general help thread.
Q1: How do I root my Samsung Galaxy S3 i9300?
There are several methods to achieve this:Q2: What can I do to conserve/improve battery life?
Official Samsung Touchwiz ROMs enable Smart Screen by default. You can tell it's enabled if you see an eye icon in the top right corner of your phones home screen. Smart Screen attempts to sense when you are looking at the screen to turn it on and to rotate the screen when you change your viewing angle but it is also notorious for draining the battery.Q3: How do I flash (install) ROMs?
To turn it off go to Settings -> My Device -> Smart Screen then disable 'Smart Stay' and 'Smart rotation'.
To conserve your battery under official firmwares it is also recommended to enable power saving mode and, for all firmwares, you should turn off the WiFi, Bluetooth and your mobile data connections whenever you are not using them to minimize battery drain.
ROMs that come packaged as a .zip file are usually installed using a custom recovery tool such as TWRP or ClockworkMod. Unlike previous Samsung Galaxy S devices the recovery for the Samsung Galaxy S3 i9300 is NOT part of the kernel. Instead, the SGSIII has a separate recovery partition. Custom recovery partitions can be installed using Odin if you are running Windows or Heimdall, which is available for Linux/UNIX and Mac OSX as well as Windows.Q4: How can I return to the stock ROM?
Some ROMs come packaged as a .tar.md5 file. These can only be directly flashed using Odin. Heimdall users are required to extract the individual tar files from within the .tar.md5 file and then flash them to the correct partitions using an appropriate .pit (partition map) file. Heimdall can be used to generate .pit files by extracting the existing partition map from your phone. Note that .tar.md5 files are actually just regular tar files with an added .md5 extension.
There is sometimes the need to revert to the stock ROM, for example when you need to return your device if its still under warranty. doovd made this great guide to the process.Q5: What is Odin?
Odin is a leaked tool from Samsung. It is used to flash firmwares (aka ROMs) to phones. There are many how-to's covering the use of Odin, such as this. Others can be found on the XDA WIKI.Q6: How do I unlock my bootloader?
There is no need to unlock the bootloader as it is already unlocked! This is the case for most Samsung devices.Q7: I have heard about EFS. Why is this so important?
/EFS is a partition on your phone where your IMEI code is stored. Without it your phone is an expensive PDA as you will not be able to make calls. Make sure to have a backup of this partition on a separate device before you attempt to flash new ROMs. TWRP and Philz recovery let you backup the EFS partition.Q8: After flashing a ROM I cannot make calls. I now get a 'Not registered on network' error on my lock screen and if I look under Settings -> About Phone -> Status my IMEI begins with 0049 and my serial number has changed to a string of zeros. How can I fix this?
The format of the EFS partition changed with the release of the MG4 modem firmware so this can cause issues if your modem version and EFS don't match. Here is an explanation of the Samsung firmware naming convention.
There are many threads on this forum suggesting this problem is caused by an EFS/modem mismatch or a corrupt EFS partition. This is a potential cause but its more likely you have flashed a ROM with the incorrect CSC (Customer Sales Code) for your phone network. For example, you can experience this error if you've flashed a BTU ROM when your network requires a H3G (Three) CSC. It can also be caused by flashing a ROM using the PDA instead of the CSC option under Odin. You can check your current CSC by dialling *#1234# or connecting your phone to Kies.Q9: I'm sure I've correctly flashed an SGSIII ROM with the right CSC for my network but why can I still not make calls?
If you flashed with Odin and you're sure you flashed a ROM with the correct CSC, the first thing to try is flashing the same ROM using Odin's CSC mode instead of PDA mode. If your phone is rooted you can try changing the CSC mode using a CSC changer app but be warned that doing so will perform a factory reset - wiping all your settings, apps, messages and locally stored contacts etc. If none of those methods restore your correct IMEI, serial and network connectivity then a number of S3 users have reported success by flashing A.S._id's rescue firmware.
If your phone was running an Android version less than v4.3 before you flashed a new ROM then you may need to install a patched modem and, if you upgraded to a newer stock ROM, a patched kernel too such as the zuluman modem FW/kernel. You will usually not need to install a patched kernel if you install CyanogenMod or a CM-based ROM. A number of kernels and modem firmwares patched for Android 4.3+ are available here.Q10: What is the best ROM for the SGSIII?
Galaxy ROMs come in two flavours. CyanogenMod-based ROMs and TouchWiz-based ROMs. CyanogenMod is completely open source and forms the basis of several derivatives such as AOKP, ParanoidAndroid and many more. These ROMs lack a number of features exclusive to Samsung's TouchWiz like Svoice, Smart Stay, S-Beam and so on. On the other hand, they generally perform better thanks to consuming less resources.Q11: Where can I download the official firmware files from?
There is no such thing as 'the best rom', it is a subjective matter. Please read this sticky thread in the General section.
Official firmware files are available here.Q12: How do I enable Debug mode?
Since Android 4.2 debug (developer) mode has been hidden by default. Debug mode can be enabled by tapping 7 times on Build number under Settings -> About Phone.Q13: How do I enter Download Mode and Recovery mode?
Make sure your phone is unplugged and powered off, then:Q14: What is the 'Flash Counter'?
Download Mode: Hold Volume down, home, and power until you see the green dude.
Recovery: Hold Volume up, home, and power for about 5 seconds then release all buttons. This might take a couple of tries.
Your phone's flash counter is triggered and incremented after installing a custom firmware. This is Samsung's way of knowing that you have modded your device. Thanks to the awesome people at XDA, this counter can be reset. Refer to this thread.Q15: What is ADB and how do I use it?
This usually occurs after upgrading to Android 4.2 when users forget to also update the recovery partition. Older recoveries can't handle the multiuser support on the sdcards so your data got repeatedly shifted to a folder named 0, resulting in /sdcard/0/0/0... etc. That is where your backups have gone! You simply have to update TitaniumBackup's settings to point to the correct location and your backups will re-appear.Q18: I have searched everywhere and still can't find an answer to my question!
Have you really searched everywhere? Google? Have you tried asking in the XDA thread relating to your problem? Have you read the stickies and FAQs? If you have honestly spent more than 5-10 minutes searching for an answer, post a new thread in the Q&A section.
A special thanks to everyone who contributed to the production of this FAQ
in particular XDA Member @pfmdan, aka Dan MacDonald / danboid who basically rewrote this entire FAQ. Please thank him for this FAQ!
Also thanks to @SkippyleGrandGourou for providing updated links to TWRP and ClockworkMod