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I am trying to unlock my bootloader, but I am unable to enable USB debugging because my device (Sony Xperia T) cannot turn on.

How do I unlock my bootloader so that I can flash it?

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  • You need to be connected to the bootloader in order to unlock it, and to do so you need to connect through fastboot. And what do you mean by not coming on?
    – esQmo_
    Commented Dec 8, 2016 at 12:53
  • In short, no usb-debugging needed in order to use fastboot. Simply boot into bootloader mode, as described behind the fastboot link.
    – Izzy
    Commented Dec 8, 2016 at 13:35

2 Answers 2

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For device recovery purposes, use original stock ROM images. Flashing of original ROM does not require an unlocked bootloader.

The bootloader being locked means that it would only allow flashing of vendor signed images. And by definition, the original images are vendor signed.

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  • That might ring true for older devices like the one OP has, but for many modern phones (e.g. the Nexus/Pixel/OnePlus families), locked bootloader means you can't even flash a factory image, and if "OEM unlocking" isn't turned on prior to this and the phone can't be powered on, one's pretty much screwed.
    – Andy Yan
    Commented Dec 9, 2016 at 7:44
  • @AndyYan, I have read a few of your posts and you seem to be a knowledgeable guy (that's more than I can say about most of the highest rated users here) but you are confused about this. I worked in the mobile devices industry for the last 15 years and I have never seen (not even heard of) a device which would not allow reflashing of it's current software build. So I stand by my original statement. You are welcome to humor me with your anecdotal evidence to the contrary and I will try to explain the actual problem in that specific case. Commented Dec 9, 2016 at 18:29
  • Well I'd also like to hear what you can do to rescue those Nexus/Pixel users doomed by a locked bootloader, non-booting OS and OEM unlocking turned off in Developer options (since it may one day happen to one of us)... Certainly this doesn't happen every day, but every time it happens, the solution reached by XDA members is sending the phone back to warranty/replacement.
    – Andy Yan
    Commented Dec 10, 2016 at 1:21
  • I kind of guessed that you would bring up Pixel. The problem with it is not that all flashing is completely disabled but rather that Google decided not to release the proper images. Commented Dec 10, 2016 at 1:52
  • Well if you put it like that... Yes in a sense, but AFAIK not just the lack of images. Qualcomm devices should all have their proprietary 9008/900E rescue modes buried somewhere, but on Nexus/Pixel devices there's no surefire way to bring 'em up. Either way, sad info for end users.
    – Andy Yan
    Commented Dec 10, 2016 at 2:57
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For Mainstream phones like the Pixel, if bootloader unlock was initially allowed from the development settings when it was on, you just simply need to get to fastboot mode if the phone has it, after downloading a custom recovery and using fastboot boot [filename] command to boot the recovery and install custom OS before looking for an official ROM.

Ensure not to flash the custom recovery since stock recovery will be needed by the phone after unlocking bootloader from fastboot mode to reset it since unlocking must erase the entire phone. Code to unlock fastboot oem unlock

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