[Help] Stuck in a boot loop, computer won't recognize phone

[inPHiniTe]

I have a d6603 Z3 on 5.1.1. I attempted to use flashtool to downgrade my firmware as per this thread: http://forum.xda-developers.com/z3/general/guide-rootrecovery-how-to-root-install-t3017056

After allowing it to flash, the last lines were:
10/058/2015 23:58:25 - INFO - Please unplug and start your phone
10/058/2015 23:58:25 - INFO - For flashtool, Unknown Sources and Debugging must be checked in phone settings

Once I did that, the phone would start and during the boot process it would freeze and restart. Connecting to my computer shows that the battery is at 50% no matter how long it's connected. I've tried holding the power button with volume up, or power with volume down, and doing those two while connecting to computer, and nothing. Pressing the yellow button and getting the vibrations don't help. Trying to use PC Companion Repair, but that's not getting anywhere because when I hold the volume button while connecting the device, it doesn't recognize the device. Sometimes the phone will vibrate once while holding volume down when I do that. Still nothing. I'm at my wits end here.

 

[sourabhp]

looks like software brick. If you havent unlocked the bootloader go to service center and get it done. but you will get latest 5.1.1.
dont tell them you used flashtool n all.

 

[inPHiniTe]

Hmm, I'll have to wait til support lines open up. I'll report back sometime in the morning/afternoon.

 

[inPHiniTe]

I've just contacted Sony. They want me to send the device in for repair. I didn't tell them what I was attempting to do, only that I was in a boot loop.

 

[maitreyodi]

I've just contacted Sony. They want me to send the device in for repair. I didn't tell them what I was attempting to do, only that I was in a boot loop.

I was in the same case and resolved it that way :
Note : locked bootloader

* installed flashtool on my computer (debian 8) : http://www.flashtool.net
* downloaded stock firmware for my isp (orange, france) : http://forum.xda-developers.com/z3/general/ftf-stock-firmwares-xperia-z3-models-t2886061
* followed http://forum.xda-developers.com/showpost.php?p=45187952&postcount=2 to flash the ftf using flashtool
* got my phone erased and back to stock KK but no more boot loop, and no sending to sony for repair.

Hope this helps and will work for you.

 

[imprezif]

If you use pc companion try going into fix phone and manually select the phone model your fixing and it should force a flash through. Your just going to have to charge it up a bit if possible.
Worked for my boot looping D6616 which I had never hooked up to pc companion before.
Best of luck

Sent from my D6616 using XDA Free mobile app