[URGENT] Help! My Xperia ZL won't boot-up unless connected to a USB power source

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My Sony Xperia ZL is NOT booting up unless it has an external power supply. The phone vibrates, shows the SONY bootscreen, and then dies. Also, the phone runs perfectly until i disconnect it and it simply dies in the blink of an eye. I have an unlocked bootloader and was on CM10.2, flashed the stock ftf for 4.3, then 4.2, and yet nothing worked! My device is just around 8 months old and i doubt that my battery can be dead all of a sudden when it was giving decent backup until today!
(couldn't get a reply on the ZL forum that's why posting here)
 

gripfly

Senior Member
Jul 13, 2013
923
465
So you can't turn on your Z without an external power supply but If you turn it on with an external power supply, you get in a bootloop?

Did I understand it correctly?