[Q] Nexus 7 2012 Wont boot after update - Nexus 7 Q&A, Help & Troubleshooting

I have been working with Android for a few years now. My Nexus 7 has no problems. A friend tried to update her 7 to 4.4.4 via the standard system update. Hers was completely stock, not rooted, not unlocked. She ended up stuck in the bootloader afterward.
The bootloader is locked. When I try to unlock it I get the following error.
(bootloader) erasing userdata...
(bootloader) erasing userdata done
(bootloader) erasing cache...
(bootloader) erasing cache done
(bootloader) unlocking...
FAILED (remote: (unknown error code))
finished. total time: 5.299s.
I have tried 2 computers, 3 usb cables. I have tried WUGS toolkit as well without luck. Nothing seems to get this bootloader unlocked.
Is there anyway to flash the factory files with a locked bootloader?
Any other options?

@gotbeer: Have you tried unlocking it with fastboot?

Sadly the string above is what I get when I used fastboot to unlock.
fastboot oem unlock
I have completely drained the battery and am going to try again. Three other Nexus 7's and a Galaxy Nexus and Ive never had a problem with unlocking the bootloader. Im beginning to suspect a hardware failure on this one.
Is there another way besides fastboot to unlock the bootloader I can try? The system partition is erased so I cant get into there to do anything. Im sure she never enabled USB debugging, so ADB is out of the question?

Related

[Q] Nexus 7 - bootloader unlock fails

My N7 may be on the way out, but I'd like to give it one last try:
For the last couple weeks it's been intermittently shutting off, or just freezing. This was happening in safe mode, too.
I did a factory reset, that seemed to help for a few days. It started acting up again, also in safe mode.
I tried one more factory reset, but that seems to have failed. I couldn't get past the Google splash screen.
I got into recovery mode and tried another reset, but couldn't get any farther than a message that said "erasing cache..." ( I have the exact message written down somewhere).
I then attempted to reflash everything. Because it's locked, I needed to unlock it first. But unlock fails.
This is what I get at "fastboot oem unlock".
I see in the upper left corner "Unlocking now......"
On the CMD window I get this:
(bootloader) erasing userdata...
(bootloader) erasing userdata done
(bootloader) erasing cache...
(bootloader) erasing cache done
(bootloader) erasing userdata...
(bootloader) unlocking...
FAILED (remote: (Unknown error code))
finished. total time: xxx s
The N7 fails to unlock. I've searched some other forums and there are some who think that it's a hardware failure. Are there any other things I can do to troubleshoot?
Try another cable, Another port on your PC... And lastly perhaps a different pc.
KJ said:
Try another cable, Another port on your PC... And lastly perhaps a different pc.
Click to expand...
Click to collapse
Have tried some different combinations - will try a few more.
No joy,
Multiple computers, multiple USB ports, multiple cables.
All result in the same thing - unable to unlock:
(bootloader) erasing userdata...
(bootloader) erasing userdata done
(bootloader) erasing cache...
(bootloader) erasing cache done
(bootloader) erasing userdata...
(bootloader) unlocking...
FAILED (remote: (Unknown error code))
finished. total time: x.xx s
Then it unfortunately sounds like hardware...
That's the direction I'm leaning. I am able to communicate with it via USB, and can get to the "are you sure you want to unlock" screen. When I select "yes" there is no data being transferred via USB, it's all an internal function that should run. But it will always fail with "unknown error".

[HELP] Soft-brick, cannot unlock bootloader

With what seems to be a soft-brick Google Nexus 7 2012 Wi-fi model, I tried going through comminus' tutorial on both my laptop and my desktop, but I end up with the following error message when I try to unlock the bootloader, an essential part to fixing my boot loop/soft-brick problem. I am unrooted, by the way, so TWRP and other custom recoveries are not an option unless there is a way to flash them via fastboot. I cannot access ADB in any way whatsoever.
Code:
android-sdk\platform-tools>fastboot oem unlock
...
(bootloader) erasing userdata...
(bootloader) erasing userdata done
(bootloader) erasing cache...
(bootloader) erasing cache done
(bootloader) unlocking...
FAILED (remote: (Unknown error code))
finished. total time: XX.XXXs
Of course, any attempt at flashing anything would result in no avail, neither:
Code:
android-sdk\platform-tools>fastboot flash bootloader bootloader-grouper-4.23.img
sending 'bootloader' (2100 KB)
FAILED (remote: Bootloader is locked.)
finished. total time: X.XXXs
android-sdk\platform-tools>fastboot -w update image-nakasi-jwr66y.zip
archive does not contain 'boot.sig'
archive does not contain 'recovery.sig'
archive does not contain 'system.sig'
———————————————————————————————————————————————————
Bootloader version...: 4.23
Baseband version.....: N/A
Serial Number........: (insert unique serial here)
———————————————————————————————————————————————————
checking product...
OKAY [ X.XXXs]
checking version-bootloader...
OKAY [ X.XXXs]
sending 'boot' (4896 KB)...
FAILED (remote: Bootloader is locked.)
finished. total time: X.XXXs
I have verified that both computers can detect my device correctly via the fastboot devices command.
I do not understand what is wrong with my device at this point. Any pointers or tips would be greatly appreciated.
Bump. I could use some help regarding this issue, preferably before I have to depart for Los Angeles on the 2nd!
RinDunois said:
Bump. I could use some help regarding this issue, preferably before I have to depart for Los Angeles on the 2nd!
Click to expand...
Click to collapse
Have you tried Wug's Toolkit? I have been here myself, checked the softbricked option and even had to flash back as far as 4.4.2. Place your device in fastboot and check the soft brick option let me know where you get with this suggestion.
I just wanted to let you know that the first thing I noticed is the following error:
FAILED (remote: Bootloader is locked.)
This has to be unlocked first before you will be able to flash the OTA. You can use wuget tool to unlock the bootloader and then try to use fastboot. Once that is done, you can relock it if you want.
PapaMag said:
Have you tried Wug's Toolkit? I have been here myself, checked the softbricked option and even had to flash back as far as 4.4.2. Place your device in fastboot and check the soft brick option let me know where you get with this suggestion.
Click to expand...
Click to collapse
That was one of the first things I tried, actually, on suggestion of some friends who have experience with the device. Sadly, none of the driver options worked nor did the softbrick option get me anywhere, so I moved onto doing it manually doing it via cmd instead.
barakisbrown said:
I just wanted to let you know that the first thing I noticed is the following error:
FAILED (remote: Bootloader is locked.)
This has to be unlocked first before you will be able to flash the OTA. You can use wuget tool to unlock the bootloader and then try to use fastboot. Once that is done, you can relock it if you want.
Click to expand...
Click to collapse
I am fully aware that I need to unlock the bootloader before doing anything. I wanted to see if the so called flash all script was going to help AFTER seeing that the unlock bootloader command did not work whatsoever as you can see in the first block of code in my post.

Soft-bricked Nexus 7 2012

I have a Nexus 7 2012 running 5.1.1 LMY47V. Product/variant grouper, bootloader version4.23.
The device is in a boot loop and performing a wipe data/factory reset (multiple tries) does not fix the issue.
I am currently trying to unlock the boot loader so I can put a new image on but the bootloader will not unlock. The output from trying is below. The dialog screen does pop up asking me to verify yes but the bootloader stays locked.
fastboot oem unlock
...
(bootloader) erasing userdata...
(bootloader) erasing userdata done
(bootloader) erasing cache...
(bootloader) erasing cache done
(bootloader) unlocking...
FAILED (remote: ()
finished. total time: 3.610s
XDA Visitor said:
I have a Nexus 7 2012 running 5.1.1 LMY47V. Product/variant grouper, bootloader version4.23.
The device is in a boot loop and performing a wipe data/factory reset (multiple tries) does not fix the issue.
I am currently trying to unlock the boot loader so I can put a new image on but the bootloader will not unlock. The output from trying is below. The dialog screen does pop up asking me to verify yes but the bootloader stays locked.
fastboot oem unlock
...
(bootloader) erasing userdata...
(bootloader) erasing userdata done
(bootloader) erasing cache...
(bootloader) erasing cache done
(bootloader) unlocking...
FAILED (remote: ()
finished. total time: 3.610s
Click to expand...
Click to collapse
Hello, and welcome to XDA!
Please wait while I connect your question to this forum (where your device experts can be found):
> Nexus 7 > Nexus 7 Q&A, Help & Troubleshooting
Note that to respond to replies, you will need to create an XDA account.
Hope this helps, and good luck!

unlocked oem but says device locked

so im trying to downgrade by flashing marshmallow
i do everything im supposed to, i unlocked oem from developers settings or by using fastboot oem unlock, but it keeps saying device locked.
whenever i try to flash something it says (bootloader) Preflash validation failed and other things.
idk what to do.
when using oem unlock my data doesnt get wiped nothing happens, in cmd it says ok but nothing changes
it says this (bootloader) Invalid signed image
(bootloader) Preflash validation failed
FAILED (remote failure)
1st
Downgrade botloader and partition table(gpt) is impossible.
2nd
What is your status code in bootloader screen? @reyfor11

How to lock bootloader without wiping?

Old thread: Unrooting gives me bootloop?
Hi there everyone,
After upgrading to Oreo, I unlocked my bootloader, flashed TWRP and Magisk. After that I did a backup of my System and Boot partitions on my currently active slot B. For some reason Slot A doesn't really boot up, so I don't really know what's up with that.
The problem is, before rooting everything was perfect and after the root I feel the instability. I've been using rooted devices for years now and I've never really had problems with the stock ROM being rooted.
So how do I unroot? Well, it's as simple as clicking Complete Unroot in Magisk. Yeah, that bootloops. Trying to flash MagiskUninstaller zip? That bootloops too. The only thing that saved me from those bootloops was that backup I did with TWRP. Yeah, that was after Magisk already had take a crap on my boot image.
Any suggestions that don't involve me losing my 30 Gigs of precious data? I would like to try with Mi Flash Tool but I'm scared from bootlooping for long periods of time (I don't have all day, after all).
New question: How to lock bootloader without wiping?
Hi there again!
I tried flashing the original system.img and boot.img from a fastboot Oreo ROM I found online. I just wanted to lock my bootloader, since currently I don't really need Root access anymore and I don't want this poor security a phone with an unlocked bootloader brings. The problem is, when I type fastboot oem lock it doesn't want to boot anymore, even without Magisk.
Does anybody know a fastboot ROM out there that can be locked? At the official MIUI.com website the fastboot ROM hasn't been updated for a very long time and I don't want to wipe my data. Does anybody have a perfectly working Oreo image that can be locked?
It bootloops, because you:
1. installed TWRP (first mod of boot.img)
2. installed Magisk (it backed up your boot.img with TWRP already installed)
3. when you uninstalled Magisk, you effectively restored boot image with TWRP, which as far as I know doesn't disable dm-verity which in turn doesn't allow boot of modified system/boot image
The safest method of unrooting is to flash stock Oreo boot.img directly via fastboot. Next time try to avoid installing TWRP (it's not needed for installing Magisk). Don't try to flash Nougat system, your data can't be read by old system anymore.
For a quick solution it should be enough to install Magisk again.
_mysiak_ said:
It bootloops, because you:
1. installed TWRP (first mod of boot.img)
2. installed Magisk (it backed up your boot.img with TWRP already installed)
3. when you uninstalled Magisk, you effectively restored boot image with TWRP, which as far as I know doesn't disable dm-verity which in turn doesn't allow boot of modified system/boot image
The safest method of unrooting is to flash stock Oreo boot.img directly via fastboot. Next time try to avoid installing TWRP (it's not needed for installing Magisk). Don't try to flash Nougat system, your data can't be read by old system anymore.
For a quick solution it should be enough to install Magisk again.
Click to expand...
Click to collapse
Thank you very much for the help! I'm gonna try this now. I'm pretty new to this A/B partitioning scheme, I knew that there isn't a recovery partition but I didn't know that TWRP is stored in Boot.img
Thanks again! Have a wonderful day/night!
_mysiak_ said:
It bootloops, because you:
1. installed TWRP (first mod of boot.img)
2. installed Magisk (it backed up your boot.img with TWRP already installed)
3. when you uninstalled Magisk, you effectively restored boot image with TWRP, which as far as I know doesn't disable dm-verity which in turn doesn't allow boot of modified system/boot image
The safest method of unrooting is to flash stock Oreo boot.img directly via fastboot. Next time try to avoid installing TWRP (it's not needed for installing Magisk). Don't try to flash Nougat system, your data can't be read by old system anymore.
For a quick solution it should be enough to install Magisk again.
Click to expand...
Click to collapse
Hey there again!
I tried to boot from the stock boot.img but it bootloops again! The backup from before is, again, what saved me.
Am I stuck now? Is there something wrong with my system.img? Or my /data partition? I'm scared of even reflashing clean.
nicolasmart said:
Hey there again!
I tried to boot from the stock boot.img but it bootloops again! The backup from before is, again, what saved me.
Am I stuck now? Is there something wrong with my system.img? Or my /data partition? I'm scared of even reflashing clean.
Click to expand...
Click to collapse
Which stock boot.img exactly did you use?
_mysiak_ said:
Which stock boot.img exactly did you use?
Click to expand...
Click to collapse
The one from the Oreo fastboot ROM. Got it from here.
nicolasmart said:
The one from the Oreo fastboot ROM. Got it from here.
Click to expand...
Click to collapse
When you ran TWRP for the first time, it asked you if you want to allow system modification (mount as R/W) - did you allow it? If yes, it has tampered your system partition and you won't be able to boot with stock boot.img due to dm-verity. Either install Magisk again or reflash stock Oreo system.img (from the link you provided).
_mysiak_ said:
When you ran TWRP for the first time, it asked you if you want to allow system modification (mount as R/W) - did you allow it? If yes, it has tampered your system partition and you won't be able to boot with stock boot.img due to dm-verity. Either install Magisk again or reflash stock Oreo system.img (from the link you provided).
Click to expand...
Click to collapse
OK, I can reinstall the system.img and boot.img via Fastboot. It won't delete any data, right?
Edit: Thanks for all your support again! You're the saviour of my Mi!
nicolasmart said:
OK, I can reinstall the system.img and boot.img via Fastboot. It won't delete any data, right?
Edit: Thanks for all your support again! You're the saviour of my Mi!
Click to expand...
Click to collapse
Your data is safe as long as you don't run incorrect command (DON'T flash userdata.img and DON'T run fastboot command with "-w" switch)
fastboot flash boot boot.img
fastboot flash system_a (and/or system_b) system.img
and you are good to go. Don't panic when system flashing will appear as stuck, it takes some time while it splits 3gb file into 6 smaller ones and starts the actual flashing.
_mysiak_ said:
Your data is safe as long as you don't run incorrect command (DON'T flash userdata.img and DON'T run fastboot command with "-w" switch)
fastboot flash boot boot.img
fastboot flash system_a (and/or system_b) system.img
and you are good to go. Don't panic when system flashing will appear as stuck, it takes some time while it splits 3gb file into 6 smaller ones and starts the actual flashing.
Click to expand...
Click to collapse
Thank you! But why should I run fastboot flash boot boot.img?? Isn't it fastboot flash boot_b boot.img? I'm on slot B currently.
nicolasmart said:
Thank you! But why should I run fastboot flash boot boot.img?? Isn't it fastboot flash boot_b boot.img? I'm on slot B currently.
Click to expand...
Click to collapse
You are right, for restore you should "fastboot flash boot_b boot.img". I was probably thinking about rooting procedure where you should use "fastboot boot boot.img"
_mysiak_ said:
You are right, for restore you should "fastboot flash boot_b boot.img". I was probably thinking about rooting procedure where you should use "fastboot boot boot.img"
Click to expand...
Click to collapse
Well, I did all that and I now have a perfectly working system with stock recovery and I think it doesn't boot loop anymore with a stock boot image. Thank you!
However, I tried to lock my bootloader via fastboot oem lock, the first time I was using some shady boot image which should be "stock" but it really wasn't, and it said "The system has been destroyed." I really laughed at this label and went into fastboot to unlock my bootloader again. I switched the boot image to a legit one which has Magisk installed, tried to lock again but this time it flashed the Mi logo for a split second and then a dark screen appeared (can somebody please explain this weird behaviour?). I really scared because the PC wasn't detecting the phone but I held the Volume Down + Power buttons for 10 seconds hoping I will see the Mi Bunny on the Fastboot. Yeah, it worked. I unlocked the bootloader again (lol) and my phone was working again!
Don't worry! My phone's still OK and 100% functioning.
The only reason I tried to lock my bootloader with Magisk installed is because somebody said it worked for them. However, now I realize how risky would that be. Whenever an OTA appears you should hope you don't get locked out of your phone.
So, people with a rooted Mi A1 - don't lock your bootloader unless you fully unroot and revert to stock!!!
How can I lock my bootloader again without wiping? (See the updated first post for more information)
nicolasmart said:
How can I lock my bootloader again without wiping? (See the updated first post for more information)
Click to expand...
Click to collapse
Just wait for an official Xiaomi fastboot Oreo ROM and either use MiFlash or included script "flash_all_except_storage.bat". It will lock bootloader at the end of flashing procedure. Though you probably won't gain much added security as you can unlock the bootloader without data wipe at any time (some reports say that you even don't need "allow oem unlock" in developer settings, but I haven't tried that).
nicolasmart said:
How can I lock my bootloader again without wiping? (See the updated first post for more information)
Click to expand...
Click to collapse
For more detailed instructions have a look over here: https://forum.xda-developers.com/mi-a1/how-to/ota-official-fastboot-image-n2g47h-7-12-t3728929
flash_all_except_storage = Keep your data, bootloader gets re-locked is the variant you are looking for.
Please keep in mind, that downgrading is not recommended. So this solution is absolutely fine when you are at 7.12.19 or below.
If you are not, you have to wait for the next fastboot update package to become available (like me)
It’s better to do a clean flash using the ROM and MiFlash provided on Xiaomi Website to ensure that the system is unmodified and you won’t get errors or bricks during a future OTA.
I don't want to clean flash. It will take forever for Xiaomi to release the new fastboot ROM
nicolasmart said:
I don't want to clean flash. It will take forever for Xiaomi to release the new fastboot ROM
Click to expand...
Click to collapse
Fastboot ROM should be out in a couple of days, usually it's released one week after first OTA update (the one from 19th December was online on 26th or 27th if I remember correctly).
Edit: Clean flash is not necessary, only full flash of all stock images, except user data.
_mysiak_ said:
Though you probably won't gain much added security as you can unlock the bootloader without data wipe at any time
Click to expand...
Click to collapse
As an old Nexus user (Nexus 7, Nexus 7 2013, Nexus 5X) I was shocked when I have found this.
_mysiak_ said:
(some reports say that you even don't need "allow oem unlock" in developer settings, but I haven't tried that).
Click to expand...
Click to collapse
Even this is true for Mi A1 in Nougat and Oreo too. So two critical security omissions by XIAOMI. One must ask himself if it is bug or strange feature
Code:
Developer options / OEM unlocking
Alow the bootloader to be unlocked - option is switched off
C:\>adb devices
List of devices attached
******** device
C:\>adb reboot bootloader
C:\>fastboot devices
******** fastboot
C:\>fastboot oem device-info
...
(bootloader) Device tampered: false
(bootloader) Device unlocked: false
(bootloader) Device critical unlocked: false
(bootloader) Charger screen enabled: false
(bootloader) Display panel:
OKAY [ 0.070s]
finished. total time: 0.073s
C:\>fastboot oem unlock
...
OKAY [ 0.153s]
finished. total time: 0.158s
C:\>fastboot oem device-info
...
(bootloader) Device tampered: false
(bootloader) Device unlocked: true
(bootloader) Device critical unlocked: true
(bootloader) Charger screen enabled: false
(bootloader) Display panel:
OKAY [ 0.069s]
finished. total time: 0.073s
C:\>fastboot reboot
rebooting...
finished. total time: 0.021s
Developer options / OEM unlocking
Bootloader is already unlocked - option is switched off
C:\>adb devices
List of devices attached
******** device
C:\>adb reboot bootloader
C:\>fastboot devices
******** fastboot
C:\>fastboot oem device-info
...
(bootloader) Device tampered: false
(bootloader) Device unlocked: true
(bootloader) Device critical unlocked: true
(bootloader) Charger screen enabled: false
(bootloader) Display panel:
OKAY [ 0.070s]
finished. total time: 0.074s
C:\>fastboot oem lock
...
OKAY [ 0.088s]
finished. total time: 0.091s
C:\>fastboot oem device-info
...
(bootloader) Device tampered: false
(bootloader) Device unlocked: false
(bootloader) Device critical unlocked: false
(bootloader) Charger screen enabled: false
(bootloader) Display panel:
OKAY [ 0.070s]
finished. total time: 0.074s
C:\>fastboot reboot
rebooting...
finished. total time: 0.020s
C:\>
_jis_ said:
As an old Nexus user (Nexus 7, Nexus 7 2013, Nexus 5X) I was shocked when I have found this.
Even this is true for Mi A1 in Nougat and Oreo too. So two critical security omissions by XIAOMI. One must ask himself if it is bug or strange feature
Code:
Developer options / OEM unlocking
Alow the bootloader to be unlocked - option is switched off
C:\>adb devices
List of devices attached
******** device
C:\>adb reboot bootloader
C:\>fastboot devices
******** fastboot
C:\>fastboot oem device-info
...
(bootloader) Device tampered: false
(bootloader) Device unlocked: false
(bootloader) Device critical unlocked: false
(bootloader) Charger screen enabled: false
(bootloader) Display panel:
OKAY [ 0.070s]
finished. total time: 0.073s
C:\>fastboot oem unlock
...
OKAY [ 0.153s]
finished. total time: 0.158s
C:\>fastboot oem device-info
...
(bootloader) Device tampered: false
(bootloader) Device unlocked: true
(bootloader) Device critical unlocked: true
(bootloader) Charger screen enabled: false
(bootloader) Display panel:
OKAY [ 0.069s]
finished. total time: 0.073s
C:\>fastboot reboot
rebooting...
finished. total time: 0.021s
Developer options / OEM unlocking
Bootloader is already unlocked - option is switched off
C:\>adb devices
List of devices attached
******** device
C:\>adb reboot bootloader
C:\>fastboot devices
******** fastboot
C:\>fastboot oem device-info
...
(bootloader) Device tampered: false
(bootloader) Device unlocked: true
(bootloader) Device critical unlocked: true
(bootloader) Charger screen enabled: false
(bootloader) Display panel:
OKAY [ 0.070s]
finished. total time: 0.074s
C:\>fastboot oem lock
...
OKAY [ 0.088s]
finished. total time: 0.091s
C:\>fastboot oem device-info
...
(bootloader) Device tampered: false
(bootloader) Device unlocked: false
(bootloader) Device critical unlocked: false
(bootloader) Charger screen enabled: false
(bootloader) Display panel:
OKAY [ 0.070s]
finished. total time: 0.074s
C:\>fastboot reboot
rebooting...
finished. total time: 0.020s
C:\>
Click to expand...
Click to collapse
Thanks for the confirmation. I consider it as a serious security flaw and was really surprised as well. I would like to know Xiaomi's reason to do it this way.. Users should be aware that they have to keep data encrypted with good PIN/pattern and request it on each boot to keep information secure.

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