Upgrade Samsung Galaxy S3 GT-I9300 To I9300XXUGOC1 (XXUGOC1) Android 4.3 Official

This post contains the manual installation or step by step guides you can follow to update your Samsung Galaxy S3 GT-I9300 to the latest and official stock firmware, I9300XXUGOC1 (XXUGOC1) Android 4.3 Jelly Bean.

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You should not skip this announcement as it's always be a recommendation for Android users to keep their device running a recent software to maintain their phone's performance and stability because the update generally comes with bugs-fix. Therefore I suggest you to upgrade your Galaxy S3 to this firmware.

Therefore you can now launch About Phone and then go to System Update to see whether there is I9300XXUGOC1 is there or simply connect your phone to computer to use the Samsung KIES utility.

However if somehow you are not being notified yet through either OTA or KIES, then you can go to manual installations from this post. Firmware file will be provided for you to download and Odin that's dedicated to flash the firmware file manually.

Are you all for it? Just read the preconditions first.

Preconditions.

1. Never try I9300XXUGOC1 if your phone is not Samsung Galaxy S3 GT-I9300. Go to About phone and see the model number there.
2. A rooted phone will lose their root access for installing this software.
3. Stock image recovery will replace your custom recovery.
4. Your phone will be detected by KIES after installing this firmware.
5. This firmware will delete your custom ROM system memory partition.
6. Enable USB debugging mode for Android Jelly Bean trough Developer Options.
7. Has enough battery percentage.
8. Odin will be used to flash the firmware.
9. Prepare your Windows computer, a USB cable and make sure have a USB drivers installed.
10. Disable KIES before installing the software.
11. Also deactivate your computer antivirus as it will try to block Odin from running.

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Download the firmware files based on your regions (extract the file).

• Greece (Cosmote) I9300XXUGOC1_I9300COSGOC1_COS.

You need to extract the file you just downloaded.

How to update Samsung Galaxy S3 GT-I9300 to Android 4.3 Jelly Bean with I9300XXUGOC1 (XXUGOC1) firmware

Step 1 - Download ODIN v3.09. Extract the zip file.

Step 2- Power off your phone then boot into Download Mode, press these buttons; Volume Down + Home + Power. Use Volume Up to enter the mode.

Step 3 - Click on Odin3 v3.0.9 from your computer to launch the tool.

Step 4 - When your phone's in Download Mode, you can connect it to computer using a USB cable. Odin will display Added!!! with ID:COM turn to yellow if the connection is successful.

Step 5 - Tap AP now then browse and click the .tar.md5 file of the firmware.

Step 6 - Leave other options intact, make sure Auto Reboot and F. Reset Time are checked.

Step 7 - You can hitting the Start button now to start the installation.

Step 8 - Now wait till the entire process finish. Your phone will reboot once it's done.

Step 9 - Done your phone is now powered with I9300XXUGOC1 (XXUGOC1) Android 4.3 Jelly Bean now.

Fix bootloop and other errors.

If your phone doesn't boot into normal mode, and get stuck in animation logo / bootloop. Perform the factory reset then, be sure you already have backups beforehand.

1. Power off your phone completely.
2. Now press Volume Up + Home + Power to enter the recovery mode. 
3. Inside the recovery mode, choose wipe data / factory reset.
4. Once the factory resetting is done, your phone will be like a new one.
5. Reboot your Samsung Galaxy S3.

Hope you will find the post useful.