HP Chromebook 14 SMB issue-Reploaced motherboard and cannot get past "gbb.flags is nonzero..." error

[Michael]

Hi all,

I am the technical support liaison at a middle school. I replaced the motherboards in a couple of out-of-warranty HP Chromebooks. When powered on, the devices default to the "Chrome OS is missing or damaged." screen with the error  gbb.flags is nonzero, etc screen. I have tried reinstalling the OS but it returns to this screen. 

I cannot access CROSH (or anything else). I used the recovery utility to try to reinstall the OS, but that did not work either. I think that the CB is is set somehow so that it cannot update its firmware and that is preventing it from moving forward. 

Any thoughts?

Michael

[Richard Barnette]

> On Mar 21, 2017, at 8:26 AM, Michael <mhwil...@bullochschools.org> wrote:
>
> Hi all,
>
> I am the technical support liaison at a middle school. I replaced the motherboards in a couple of out-of-warranty HP Chromebooks. When powered on, the devices default to the "Chrome OS is missing or damaged." screen with the error gbb.flags is nonzero, etc screen. I have tried reinstalling the OS but it returns to this screen.
>

Replaced the motherboards? Oy. You'll need to make sure
the BIOS and EC firmware are properly flashed. I suspect
that firmware images not signed by Google are the reasons
you can't use recovery.

Note also that if the motherboards aren't identical to the
original parts, you may have trouble getting signed firmware
to work. Signed firmware is designed for one particular
hardware configuration, and may not work with others.

> I cannot access CROSH (or anything else). I used the recovery utility to try to reinstall the OS, but that did not work either. I think that the CB is is set somehow so that it cannot update its firmware and that is preventing it from moving forward.
>

This is tricky. If you do the wrong thing, your device could
become a brick. I don't know enough to advise on the right
thing.

Are you able to switch the devices into dev mode? That ought
to work, even in the current state, and should allow some
poking around for diagnosis.


> Any thoughts?
>
> Michael
>
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> <IMG_20170321_103521789_HDR (1).jpg>

[Michael]

The kid brought the CB to me already bricked, i am trying to resurrect it. 

I think the issue is the device is in verified mode and therefore I cannot clear the firmware flags (whatever that means-I haven't got there yet!). I have been trying to figure out how to get it out of Verified and into Developer, but haven't had any success. I talked to our IT depart and all he could do is move it to a user group where dev mode is enabled.

[Mike Frysinger]

gbb 0x39 -> 0011 1001 ->

GBB_FLAG_DEV_SCREEN_SHORT_DELAY 0x1

GBB_FLAG_FORCE_DEV_SWITCH_ON 0x8

GBB_FLAG_FORCE_DEV_BOOT_USB 0x10

GBB_FLAG_DISABLE_FW_ROLLBACK_CHECK 0x20

so looks to me like this device is already forced to go to dev mode :)

after you reinstall with the recovery image, hit ctrl+d to boot it, and then:

- go into guest mode

- open crosh

- open a shell

- run `/usr/share/vboot/bin/set_gbb_flags.sh 0`

you'll need to make sure the write-protect switch has been disabled first.  once you've cleared the gbb flags, you can turn back on the wp, and you should be good to go.

you can check wp status with:

crossystem | grep wp

-mike

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[Michael]

I have tried the ESC + Refresh+ Power, CTRL + D method and it still brings me back to the "Owner has disabled dev mode" screen. 

Anyway, I know a lot more than I did this time yesterday. Thanks for helping me out. I think put this one aside for now. 

On Tuesday, March 21, 2017 at 11:26:14 AM UTC-4, Michael wrote: