[SOLVED] How to fix the Bootloop issue on Sony Ericsson Xperia Arc S LT18i usually brought about by switching on Bluetooth

Submitted by anto on Tue, 07/21/2015 - 06:54

The Sony Ericsson Xperia Arc S LT18i, an excellent phone of its times, is still a pretty decent phone to live with with all that Sony goodness in it.

The only sadness is that the item is out of support - both on the software as well as hardware sides, primarily because Sony and Ericsson parted ways.
The last available software update (Build number 4.1.B.0.587) is based on Android 4.0.4, and works good except for a few critical bugs that the unsupported users now have to live with.

One of the biggest problems is that the phone enters a 'bootloop' (reboots, after some delay turning the screen on, shows a black screen with the Sony logo, and a bit later, another screen with the Xperia logo, and then restarts, and this keeps happening again and again until you pull out the battery to power it off).

None of the normal stock methods seem to be able to fix this - hard resetting / recovery mode / PC Companion mode /....
Thanks to Androxyde's Flash Tool (www.flashtool.net), we now have the following working method to fix this.

Note that this will wipe all your data - this does a factory reset to the phone. Given the currently useless state, that seems a pretty good bargain. :-)

0. Make sure your phone battery has enough charge to complete the flashing process. Else, you might end up bricking the phone irreversibly. Keep it charging for around 1 hour or more - that should give it enough juice to live through this.
1. The flashtool works great on Windows 7.
2. Download the flashtool utility and the firmware from:
Flashtool Utility: Download the Windows version from http://www.flashtool.net/downloads.php.
Firmware for LT18i (LT18i_4.1.B.0.587_Generic Global World.ftf - 379MB - hosted on Google Drive): https://docs.google.com/file/d/0B-EZb_6TCqCiWThCcWdTNXFmQnM
3. Install the Flashtool utility by opening the downloaded installation file.
4. You Exit Sony PC Companion and any other Flashing software if you have them open / running in the background.

5. Power off the device by pulling out the battery.
6. Insert both a sim card, and an SD card.
7. Put the battery back in. DO NOT SWITCH IT ON OR PRESS ANY BUTTON.
8. Now start the FlashTool utility from the Windows "Start" menu.
9. Wait for the application to sync devices from Github.
10. Once that is over, keep the Back button on the phone pressed, and connect the USB data cable. The indicator LED, near the micro USB port on the phone, will show a green color.
11. Click on the Flash button (the one with a lightning symbol in the toolbar of the application).
12. In the 'Bootmode Chooser' dialog box that comes up, select "Flashmode" and click OK.
13. In the 'Firmware Selector' window that opens up, against 'Source Folder', select the folder where you have downloaded the firmware file to.
14. Now click the Flash button.
15. If they ask you to disconnect and reconnect the cable, do as we did in the above steps, and following the instructions shown.
16. Now when the log window shows "INFO - Flashing Finished.", and "INFO - Please unplug and start your phone", disconnect the USB cable, and switch on the mobile phone.

That should do it. You should now see a fresh and working OS booting up.

Flashing Steps (Screenshots):