[Xperia SP Q&A, Help & Troubleshooting] Ham_is_here:
https://talk.sonymobile.com/t5/Xperia-SP/xperia-sp-soft-bricked/td-p/550043

I found the same solution here.

Links work there.

---------- Post added at 08:42 PM ---------- Previous post was at 07:45 PM ----------

In case someone doesn't get what he is saying.. I am translating for you guys.

[MENTION=5713756]malla69[/MENTION] gets full credit for this solution.

SOLVED and here's the solution after continuously researching and working on it for days

How to charge your softbricked Sony Xperia SP with dead battery.

SYMPTOMS - LED changes from bright RED to DIMMED RED to GREEN to SWITCHED OFF and blinking GREEN again like 5 times

and this loop continues.

This indicates that the battery is critically low .

As my device suffered a soft brick, the system won't allow the charger or via pc connections to charge the battery (In the SONY logo state) since system of phone is corrupted.

Solution 1 (If you have charge left in your phone): Set your device to

flashmode and use the remaining charges of battery carefully for flashing with SUS (Sony Update Service)

NOTE : SUS does not support bootloader unlocked devices. You will have to re-lock bootloader to use SUS.

Alternatively you can use other flashtools carefully because if your battery dies you will rarely have a chance to charge your phone again.

SOLUTION 2 (if your battery is dead):

This guide is for charging your battery when your device is softbricked and completing flashing your device back to stock

*found after lots of experiments*

NOTE : Charging whole day and nights was useless in my case

STEPS:

1-) First download SUS (Sony Update Service) and install it

2-)Download this RAR file which contains Flash tool 0.9.11.0 and unrar with WinRAR(Paid app) or 7zip(Free app)

3-) Install the flashtool inside the RAR file and copy the three .ftf files which contain kernels to the "firmwares" folder of Flashtool installation folder (Default location :-C:\Flashtool\firmwares)

4-) Charge your device.

When it charges even just 1% or 2%. It can remain in download mode for 30 secs or 1 min and as mentioned before, the changing LED loop starts. Which won't allow you to keep the device in download mode.

4-) Open Flash tool and connect your device in flashmode by holding volume down button and USB connect ( as your device with little charge can get to download mode just for a short moment.)

DO THE FOLLOWING STEPS VERY QUICKLY BECAUSE YOU HAVE LITTLE TIME

5 -) Hit 'flash' (Thunderbolt icon) button in flash tool as device is detected and choose flashmode and choose one of the three kernels.

NOTE there will be a x10 BLRELOCK on the list. DO NOT FLASH THAT.

According to your firmware version, One FTF will surely work out and your device will switch off after flashing is successful

6-) Unplug your device from your PC.

7-) Now be careful. DO NOT SWITCH YOUR PHONE ON otherwise the whole process will have to be repeated

8-) Plug your device to a wall charger.

The device will now charge. Let it charge till full battery

AFTER CHARGING to 100%

9-) Put the device in Flashmode again

10-) Use SUS to reinstall your phone's software

NOTE - Any Data on the device will be wiped and the latest updated software for your device will be installed

TADA now after installing firmware with SUS your phone is alive. Guys, I have suffered and nothing worked quite well because it was a different case for me. The changing LEDs case. After searching hints and putting a lot of time I got the point and just don't want you people to suffer like me

Hence I posted this solution for future seekers.