If anyone is willing to unlock bootloader of their Sony Xperia ion then they can refer to the below steps, I also wanted to add that Xperia ion has not been listed for supporting bootloader unlocking on Sony’s Bootloader Unlock page but you can still follow the below steps for unlocking & relocking bootloader of Xperia ion. Just make sure that you are backing up all the data before unlocking bootloader as you will be losing your stored data in the phone. You don’t need to worry about the data in SDCARD as it will remain untouched.

Benefits of unlocking bootloader:
  • One can flash custom ROMs/Kernels
  • One will be able to try out beta builds of latest OS that is revealed by SE/Sony and requires unlocked bootloaders
  • One can root their device anytime after unlocking bootloaders.

Things that are needed before unlocking bootloader:
  • IMEI code - You can get your IMEI code by typing *#06# in phone dialer.
  • Fastboot package with usb drivers - you can get the fastboot package with usb drivers from here
  • Windows PC and an usb for connecting the phone to the computer
  • Turn off your phone while keeping the Volume Up button pressed and connect the phone to your computer for enabling FASTBOOT mode. Once the FASTBOOT mode gets enabled then windows will start the installation of the driver, at browsing point you just have to extract fastboot_with_Android_USB_file.rar that you will get from the above link and point the driver installation process to fastboot folder.
  • When the installation of the driver gets completed then you can disconnect your phone, turn it on and proceed with the steps for unlocking bootloader.

unlocking bootloader:
  • Go to this site and go through the details that has been mentioned there and then click on “Start unlocking the bootloader” at the bottom of the page. You will have to make sure whether your phone bootloader can be unlocked or not and for that you will have to check out the service menu. Just enter *#*#7378423#*#* from the phone dial pad for accessing the service menu and go in to service menu. If you see Bootloader unlock allowed - “Yes” then you can unlock bootloader of your phone, if it says no then you cannot.
  • Once you have confirmed that you are allowed to unlock the bootloader of your phone then just scroll to the bottom of that page and click on Continue. When you get a prompt saying “"Are you sure you want to unlock the bootloader” then click on yes and accept the "legal terms" as well.
  • If you have done things correctly then you will get a page saying “"Create Unlock request". So now enter the details that it will ask like IMEI number of your phone, name, email address etc and proceed. You will now see your unique unlock key displayed on screen so just make a note of it somewhere.
  • Now open fastboot folder that you might have got after extracting fastboot_with_Android_USB_file.rar, Hold SHIFT button and right click on the background of fastboot folder and open command window there. Once the command window gets opened then connect your phone in fastboot mode as mentioned in the above steps.
  • After that type “fastboot.exe -i 0x0fce getvar version” without the quotes in command window, if you get return value as 0.5 then you phone is connected properly. If it displays anything than that then reconnect your phone and type in the command again.
  • When you are done until here then type “fastboot.exe -i 0x0fce oem unlock 0xKEY” without the quotes where KEY is the unlock key that you have received after filling in the details, which will make your command look like “fastboot.exe -i 0x0fce oem unlock0x123456789”. After running the command with key your phone bootloader will be unlocked.

Relocking bootloader:
  • First download and install the latest version of FlashTool and then download LT28-ION_Relock_bootloader_Dogsly-TEST.ftf // Mirror 1.
  • When you are ready with the same then you just have to flash the FTF that you have downloaded with latest version of FlashTool. When it will say enter flashmode than simply let your phone enter flashmode following the solution that has been mentioned above for that.
  • Once the file gets flashed then you can simply reboot your phone and have your Bootloader relocked.

If at all your phone doesn’t boot then you can flash stock firmware FTF for getting back to the stock ROM without any issues.