[GUIDE][Osprey] Fastboot Flashing Factory Firmware Images

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hammy434

Member
Dec 30, 2014
28
0
Leicester
Hi, I get the following error:

"fastboot flash partition gpt.bin
target reported max download size of 268435456 bytes
sending 'partition' (32 KB)...
OKAY [ 0.005s]
writing 'partition'...
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 0.407s"

My bootloader is unlocked. Any suggestions?

Thanks
 

savvy54

Senior Member
Apr 8, 2014
54
7
Kolkata
Hello, today i received a dead Moto G 2015 (XT1550) from my friend which, he wants to know, whether can be recovered or not.:confused: So far i can only go into bootloader mode BUT not into recovery. Bootloader is locked also. I have tried flashing stock firmware using fastboot, mfastboot & RSD Lite. But all failed. :( Not a single command comes with "OKAY". :silly:
Getvar shows the following :
(bootloader) version: 0.5
(bootloader) version-bootloader: moto-msm8916-80.CC
(bootloader) product: osprey
(bootloader) board: osprey
(bootloader) secure: yes
(bootloader) hwrev: 0x82B0
(bootloader) radio: 0x9
(bootloader) emmc: 16GB Micron REV=07 PRV=10 TYPE=57
(bootloader) ram: 2048MB Elpida S8 SDRAM DIE=8Gb
(bootloader) cpu: MSM8916
(bootloader) serialno: ZY2227CBBL
(bootloader) cid: 0x0007
(bootloader) channelid: 0xc0
(bootloader) uid: 566D990F00000000000000000000
(bootloader) unlocked: no
(bootloader) securestate: locked
(bootloader) iswarrantyvoid: no
(bootloader) mot_sst: 0
(bootloader) max-download-size: 268435456
(bootloader) reason: Volume down key pressed
(bootloader) imei: 352356071331318
(bootloader) meid:
(bootloader) date: 10-28-2015
(bootloader) sku: XT1550
(bootloader) battid: SNN5965A
(bootloader) iccid:
(bootloader) cust_md5:
(bootloader) max-sparse-size: 268435456
(bootloader) current-time: "Wed Oct 28 22:43:31 UTC 2015"
(bootloader) ro.build.fingerprint[0]: motorola/osprey_retasia_ds_2gb/osp
(bootloader) ro.build.fingerprint[1]: rey_ud2:6.0.1/MPIS24.107-55-2-5/2:
(bootloader) ro.build.fingerprint[2]: user/release-keys
(bootloader) ro.build.version.full[0]: Blur_Version.24.201.5.osprey_reta
(bootloader) ro.build.version.full[1]: sia_ds_2gb.retasia.en.03
(bootloader) ro.build.version.qcom[0]: AU_LINUX_ANDROID_LA.BR.1.1.3_RB1.
(bootloader) ro.build.version.qcom[1]: 05.01.00.032.015
(bootloader) version-baseband[0]: M8916_2020632.44.03.21.54R OSPREY_APAC
(bootloader) version-baseband[1]: _CUST
(bootloader) kernel.version[0]: Linux version 3.10.49-g80097ed (hudsoncm
(bootloader) kernel.version[1]: @ilclbld31) (gcc version 4.8 (GCC) ) #1
(bootloader) kernel.version[2]: SMP PREEMPT Mon Nov 7 11:00:51 CST 2016
(bootloader) sbl1.git: sbl1.git
(bootloader) rpm.git: rpm.git
(bootloader) tz.git: tz.git
(bootloader) hyp.git: hyp.git
(bootloader) aboot.git: git=MBM-NG-V80.CC-0-gdfaac1d
(bootloader) partition-type:modem: raw
(bootloader) partition-type:sbl1: raw
(bootloader) partition-type:DDR: raw
(bootloader) partition-type:aboot: raw
(bootloader) partition-type:rpm: raw
(bootloader) partition-type:tz: raw
(bootloader) partition-type:hyp: raw
(bootloader) partition-type:utags: raw
(bootloader) partition-type:misc: raw
(bootloader) partition-type:padA: raw
(bootloader) partition-type:abootBackup: raw
(bootloader) partition-type:rpmBackup: raw
(bootloader) partition-type:tzBackup: raw
(bootloader) partition-type:hypBackup: raw
(bootloader) partition-type:utagsBackup: raw
(bootloader) partition-type:logs: raw
(bootloader) partition-type:frp: raw
(bootloader) partition-type:padB: raw
(bootloader) partition-type:modemst1: raw
(bootloader) partition-type:modemst2: raw
(bootloader) partition-type:hob: raw
(bootloader) partition-type:dhob: raw
(bootloader) partition-type:fsg: raw
(bootloader) partition-type:fsc: raw
(bootloader) partition-type:cid: raw
(bootloader) partition-type:metadata: raw
(bootloader) partition-type:logo: raw
(bootloader) partition-type:clogo: raw
(bootloader) partition-type:persist: raw
(bootloader) partition-type:kpan: raw
(bootloader) partition-type:boot: raw
(bootloader) partition-type:recovery: raw
(bootloader) partition-type:ssd: raw
(bootloader) partition-type:padC: raw
(bootloader) partition-type:sp: raw
(bootloader) partition-type:keystore: raw
(bootloader) partition-type:eek:em: raw
(bootloader) partition-type:carrier: ext4
(bootloader) partition-type:customize: raw
(bootloader) partition-type:cache: raw
(bootloader) partition-type:system: raw
(bootloader) partition-type:userdata: raw
(bootloader) partition-size:modem: 0x00000000027e0000
(bootloader) partition-size:sbl1: 0x0000000000080000
(bootloader) partition-size:DDR: 0x0000000000020000
(bootloader) partition-size:aboot: 0x0000000000113000
(bootloader) partition-size:rpm: 0x000000000003e800
(bootloader) partition-size:tz: 0x000000000008c000
(bootloader) partition-size:hyp: 0x0000000000020000
(bootloader) partition-size:utags: 0x0000000000080000
(bootloader) partition-size:misc: 0x0000000000080000
(bootloader) partition-size:padA: 0x000000000036f000
(bootloader) partition-size:abootBackup: 0x0000000000113000
(bootloader) partition-size:rpmBackup: 0x000000000003e800
(bootloader) partition-size:tzBackup: 0x000000000008c000
(bootloader) partition-size:hypBackup: 0x0000000000020000
(bootloader) partition-size:utagsBackup: 0x0000000000080000
(bootloader) partition-size:logs: 0x0000000000200000
(bootloader) partition-size:frp: 0x0000000000080000
(bootloader) partition-size:padB: 0x000000000022f000
(bootloader) partition-size:modemst1: 0x0000000000180000
(bootloader) partition-size:modemst2: 0x0000000000180000
(bootloader) partition-size:hob: 0x000000000007a000
(bootloader) partition-size:dhob: 0x0000000000008000
(bootloader) partition-size:fsg: 0x0000000000300000
(bootloader) partition-size:fsc: 0x0000000000000400
(bootloader) partition-size:cid: 0x0000000000020000
(bootloader) partition-size:metadata: 0x0000000000080000
(bootloader) partition-size:logo: 0x0000000000400000
(bootloader) partition-size:clogo: 0x0000000000400000
(bootloader) partition-size:persist: 0x0000000000800000
(bootloader) partition-size:kpan: 0x0000000000800000
(bootloader) partition-size:boot: 0x0000000001000000
(bootloader) partition-size:recovery: 0x0000000001019000
(bootloader) partition-size:ssd: 0x0000000000002000
(bootloader) partition-size:padC: 0x000000000087e000
(bootloader) partition-size:sp: 0x0000000000800000
(bootloader) partition-size:keystore: 0x0000000000800000
(bootloader) partition-size:eek:em: 0x0000000001000000
(bootloader) partition-size:carrier: 0x0000000001000000
(bootloader) partition-size:customize: 0x0000000002000000
(bootloader) partition-size:cache: 0x0000000010000000
(bootloader) partition-size:system: 0x0000000091000000
(bootloader) partition-size:userdata: 0x00000002fb3e0000
(bootloader) qe: qe 0/0
(bootloader) frp-state: no protection (err)
(bootloader) ro.carrier: retin
all: listed above
finished. total time: 0.641s

Any hope ? :D Do let me know if any info is needed.
 
Last edited:

savvy54

Senior Member
Apr 8, 2014
54
7
Kolkata
Did you try this build:
XT1550_OSPREY_RETASIA_DS_2GB_6.0.1_MPI24.107-55-2_cid7 ? @savvy54
Yeah, that was the version i tried flashing. Checked with md5sum also before flashing.
Problem is not a single command comes with an [OKAY], whether it is flashing stock recovery or flashing partition. I don't know what to do at this point..:confused:
 

dzidexx

Senior Member
Nov 9, 2015
1,694
522
Lublin, Poland
U have locked bootloader, u can flash only the same or upper version of system.

Gpt, bootloader can end with error. Rest should be OK.
If not - u can't flash anything.
Maybe u should start with:
fastboot oem fb_mode_set
fastboot oem lock begin
.
all fastboot commands
.
fastboot oem lock
 
Last edited:

savvy54

Senior Member
Apr 8, 2014
54
7
Kolkata
Thank you for your time trying to help me.

U have locked bootloader, u can flash only the same or upper version of system.

ro.build.fingerprint[1]: rey_ud2:6.0.1/MPIS24.107-55-2-5/2 : current build of the phone
I guess i am stuck now unless i get an updated firmware to flash via fastboot.

---------- Post added at 03:53 PM ---------- Previous post was at 03:49 PM ----------

Edit: Found it after hours of search on and off. Tested and is real MPIS24.107-55-2-17 19.

Do you mind sharing the link ?
 

kayyappan

Senior Member
Mar 10, 2011
542
134
Thank you for your time trying to help me.



ro.build.fingerprint[1]: rey_ud2:6.0.1/MPIS24.107-55-2-5/2 : current build of the phone
I guess i am stuck now unless i get an updated firmware to flash via fastboot.

---------- Post added at 03:53 PM ---------- Previous post was at 03:49 PM ----------



Do you mind sharing the link ?

I couldn't recover my phone using that. It kept asking for previous id which the phone was logged in with. Though I used proper id it was not getting accepted. I've dumped the phone.
If I remember right, I got it from another forum called forum.gsmhosting.com. Please search for MPIS-24.107-55-2-17 19 you'll will find XT1550 fw listed there in that forum.
Since it didn't work for me I didn't post a direct link then too to avoid messing other's units. Hope you do understand and you'll be flashing at your own risk.

Edit: Edited post to reflect correct MPIS FW that I flashed.
 
Last edited:

kayyappan

Senior Member
Mar 10, 2011
542
134
Thank you for your time trying to help me.



ro.build.fingerprint[1]: rey_ud2:6.0.1/MPIS24.107-55-2-5/2 : current build of the phone
I guess i am stuck now unless i get an updated firmware to flash via fastboot.

---------- Post added at 03:53 PM ---------- Previous post was at 03:49 PM ----------



Do you mind sharing the link ?

Found one at

https://androidfilehost.com/?fid=889764386195908045

It is
osprey_retasia_ds-user 6.0.1 MPIS24.107-55-2-17 19.zip

Good Luck.
 

savvy54

Senior Member
Apr 8, 2014
54
7
Kolkata
Here are the newest versions
Tried flashing XT1550_OSPREY_RETASIA_DS_6.0.1_MPIS24.107-55-2-5_cid7_subsidy-DEFAULT_CFC.xml
Error i am getting :
(bootloader) Failed to erase partition
(bootloader) Failed to flash partition recovery
FAILED (remote failure)

It is worth mentioning that i am not getting error related to downgradation of bootloader, gpt.....

---------- Post added at 02:11 AM ---------- Previous post was at 02:09 AM ----------

Found one at

https://androidfilehost.com/?fid=889764386195908045

It is
osprey_retasia_ds-user 6.0.1 MPIS24.107-55-2-17 19.zip

Good Luck.
This is not flashable via fastboot i think. Only 313.3 MB.

PS : Do let me know if this discussion is being offtopic here.
 
Last edited:

motog3honor

New member
Jan 11, 2019
2
1
Question concerning flashing

Hi there,

I softbroke my Moto G3 when removing SD card deleting some essential Apks. Now I want to reflash the original firmware with the help of this thread.

One thing I don't understand:

First it reads:

"WARNING: You must perform a 'Factory data reset' in Stock Recovery before flashing any Firmware Image"

If I look there it reads:

Factory data reset via Stock Recovery:
(1) Flash via fastboot stock recovery.img (found in firmware image zip)
(2) Turn your phone off.
(3) Press and hold Volume DOWN + POWER.
(4) In recovery menu press Volume down twice.
(5) Press power. You will see a red exclamation mark.
(6) Hold power down, then tap Volume UP.
(7) Go to Wipe data / Factory reset and press power button.
(8) Scroll to Yes - delete all user data and press power.

Ok, what does no. 1 one mean? So do I have to flash recovery.img first, and than go to 3) Fastboot Commands?

So No.1, flashing recovery.img is done by going to Bootloader mode and then executing

"fastboot flash bootloader recovery.img"? Or do I have to perform "fastboot flash recovery recovery.img" ?

So I have to flash recovery.img twice? One before the actual flashing, and then during the flashing?

Because there's the command again:

"fastboot oem fb_mode_set
fastboot flash partition gpt.bin
fastboot flash bootloader bootloader.img
fastboot flash logo logo.bin
fastboot flash boot boot.img
fastboot flash recovery recovery.img.
[...]"

Bit confused here...
 

Gravemind2015

Senior Member
Dec 1, 2015
1,846
862
Hi there,



I softbroke my Moto G3 when removing SD card deleting some essential Apks. Now I want to reflash the original firmware with the help of this thread.



One thing I don't understand:



First it reads:



"WARNING: You must perform a 'Factory data reset' in Stock Recovery before flashing any Firmware Image"



If I look there it reads:



Factory data reset via Stock Recovery:

(1) Flash via fastboot stock recovery.img (found in firmware image zip)

(2) Turn your phone off.

(3) Press and hold Volume DOWN + POWER.

(4) In recovery menu press Volume down twice.

(5) Press power. You will see a red exclamation mark.

(6) Hold power down, then tap Volume UP.

(7) Go to Wipe data / Factory reset and press power button.

(8) Scroll to Yes - delete all user data and press power.



Ok, what does no. 1 one mean? So do I have to flash recovery.img first, and than go to 3) Fastboot Commands?



So No.1, flashing recovery.img is done by going to Bootloader mode and then executing



"fastboot flash bootloader recovery.img"? Or do I have to perform "fastboot flash recovery recovery.img" ?



So I have to flash recovery.img twice? One before the actual flashing, and then during the flashing?



Because there's the command again:



"fastboot oem fb_mode_set

fastboot flash partition gpt.bin

fastboot flash bootloader bootloader.img

fastboot flash logo logo.bin

fastboot flash boot boot.img

fastboot flash recovery recovery.img.

[...]"



Bit confused here...
Yes.
1. Flash recovery via fastboot in bootloader (i.e fastboot) mode. To do that, power off>press power+volume down>an android would come on the screen with device details>connect to pc>open command prompt where adb.exe and fastboot.exe are located>execute-
Code:
 fastboot flash recovery recovery.img

(Assuming you've copied the firmware files to the location where fastboot.exe resides. Or else just copy fastboot, adb and 2 driver dlls into the folder where you've extracted the firmware and open command prompt from there)

Then scroll down in the phone (using volume down) till the text on the right shows "recovery". Press power to boot to recovery. Then if you only see "no command", press and hold power button and press volume up once, then release both keys. The menus should now be visible. Factory reset. Then poweroff again (you can long press power button for about 8-10 seconds for this).

Then boot again into the bootloader mode and start with flashing. You'll already have the stock recovery but it's included for a sense of complete flash (I think).

Hope it helps.

Broadcasted from Zeta Reticuli
 
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motog3honor

New member
Jan 11, 2019
2
1
Yes.
1. Flash recovery via fastboot in bootloader (i.e fastboot) mode. To do that, power off>press power+volume down>an android would come on the screen with device details>connect to pc>open command prompt where adb.exe and fastboot.exe are located>execute-
Code:
 fastboot flash recovery recovery.img

(Assuming you've copied the firmware files to the location where fastboot.exe resides. Or else just copy fastboot, adb and 2 driver dlls into the folder where you've extracted the firmware and open command prompt from there)

Then scroll down in the phone (using volume down) till the text on the right shows "recovery". Press power to boot to recovery. Then if you only see "no command", press and hold power button and press volume up once, then release both keys. The menus should now be visible. Factory reset. Then poweroff again (you can long press power button for about 8-10 seconds for this).

Then boot again into the bootloader mode and start with flashing. You'll already have the stock recovery but it's included for a sense of complete flash (I think).

Hope it helps.

Broadcasted from Zeta Reticuli

Thanks for your help, I've done that and everything went fine!
 
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Reactions: Gravemind2015

arom219

Member
Feb 19, 2018
14
3
Bogotá
First of all, thank to all the people who have contributed to this thread.

I need a little help, please. I have a Moto G3 XT1543 1GB with TWRP Recovery and SU-rooted LineageOS 14.1 Nougat and I need to flash its stock firmware. I understand almost all the steps described on this thread, but I don't know how to proceed taking into account that my Moto G3 device has both custom recovery and custom ROM. How should I start?
 
Last edited:

SpiralX15

Senior Member
Oct 14, 2014
269
26
Kolkata
First of all, thank to all the people who have contributed to this thread.

I need a little help, please. I have a Moto G3 XT1543 1GB with TWRP Recovery and SU-rooted LineageOS 14.1 Nougat and I need to flash its stock firmware. I understand almost all the steps described on this thread, but I don't know how to proceed taking into account that my Moto G3 device has both custom recovery and custom ROM. How should I start?

The flashing process will flash both the stock recovery and rom. So you need not worry about either. Just follow the steps. First the recovery will be flash. All you need to do is boot to bootloader mode and use the instructions. Do not attempt to flash the bootloader though.
 

xperia_bird

Senior Member
Apr 15, 2014
330
72
Can someone help me make a batch file for my device. my stock rom contains different kind of files. is it possible?
 

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  • 135
    Disclaimer: I am not responsible for anything that happens as a result of flashing these files. Your destiny is your own.

    Based on existing tutorial by @t-bon3. This guide has been created as a hard-brick occurred using the old Moto G (1st Gen) tutorial. Please exercise extreme care with Fastboot, and only use the commands mentioned here. Experimenting with Fastboot commands can seriously damage your phone.


    How to Fastboot Flash Moto G (3rd Gen) Factory Firmware Images

    Required Files:
    Motorola Drivers: Download
    Latest Fastboot | ADB (Windows | Linux): Download (Windows 10 users may need this pack for Drivers to work.)
    Factory Firmware Images: [INDEX][Osprey] Moto G Factory Firmware Images

    WARNING: You must perform a 'Factory data reset' in Stock Recovery before flashing any Firmware Image - instructions here.


    Instructions:

    1) Extracting Fastboot and Firmware Images:
    Extract zip for chosen Firmware Image to a folder with a simple directory structure. For example: C:\motog_firmware\
    Extract the adb-fastboot-latest_win_linux.zip into this folder.​

    2) Reboot the phone into 'Bootloader mode' and preparing PC for flashing

    Windows:
    Entering Fastboot mode:
    ------------------------------------
    i) The 'hardware' way.

    a) Unplug the USB cable and power off the phone.
    b) Press and hold 'Volume down' then power on the phone.
    c) Connect USB cable to your computer.

    ii) The 'software' way.

    a) Enable developer mode on the Moto G (Settings-> 'About Phone'. Tap 7 times on 'Build Number')
    b) Enable USB debugging. (Settings -> 'Developer options' -> 'USB Debugging' -> check)
    c) Connect phone to computer via USB, you should see a new ADB device detected and drivers installed.
    d) Open Command Prompt, navigate to the Firmware / ADB folder (i.e CD C:\motog_firmware ) and type:

    Code:
    adb reboot-bootloader
    Linux:
    Entering Fastboot mode:
    ------------------------------------
    i) The 'hardware' way.

    a) Unplug the USB cable and power off the phone.
    b) Press and hold 'Volume down' then power on the phone.
    c) Connect USB cable to your computer.

    ii) The 'software' way. (Requires ADB to be already installed - see below)

    a) Enable developer mode on the Moto G (Settings-> 'About Phone'. Tap 7 times on 'Build Number')
    b) Enable USB debugging. (Settings -> 'Developer options' -> 'USB Debugging' -> check)
    c) Connect phone to computer via USB
    d) Navigate to the Firmware folder, right-click and open terminal and type:

    Code:
    adb reboot-bootloader

    Installing ADB / Fastboot:
    -------------------------------------
    Flashing via Linux LiveCD: (Put factory firmware files on an external usb drive / pen)
    --------------------------------
    a) Download Ubuntu LiveCD
    b) Burn to DVD or write to USB pen
    c) Restart PC, Boot from DVD into Ubuntu
    d) Open Terminal and type the following:
    sudo add-apt-repository ppa:nilarimogard/webupd8
    sudo apt-get update
    sudo apt-get install android-tools-adb android-tools-fastboot​

    e) Test fastboot by typing: sudo fastboot devices
    You should see:
    <serial number> fastboot​
    f) You are now ready to flash the fastboot files


    3) Fastboot Commands:

    Do commands manually, one at a time - checking that each one returns an [OKAY].​

    NOTE: Do not simply copy and paste these commands! - system.img_sparsechunks may differ in number and name.
    Always check contents of folder you're working with. You must flash all of the sparsechunk files you have.

    fastboot oem fb_mode_set
    fastboot flash partition gpt.bin
    fastboot flash bootloader bootloader.img
    fastboot flash logo logo.bin
    fastboot flash boot boot.img
    fastboot flash recovery recovery.img
    fastboot flash system system.img_sparsechunk.0
    fastboot flash system system.img_sparsechunk.1
    fastboot flash system system.img_sparsechunk.2
    fastboot flash system system.img_sparsechunk.3
    fastboot flash system system.img_sparsechunk.4
    fastboot flash system system.img_sparsechunk.5
    fastboot flash system system.img_sparsechunk.6
    fastboot flash system system.img_sparsechunk.7
    fastboot flash system system.img_sparsechunk.8
    fastboot flash modem NON-HLOS.bin
    fastboot erase modemst1
    fastboot erase modemst2
    fastboot flash fsg fsg.mbn
    fastboot erase cache
    fastboot erase userdata
    fastboot erase customize
    fastboot erase clogo
    fastboot oem fb_mode_clear
    fastboot reboot​

    ALWAYS CHECK YOUR MODEL
    FLASHING WRONG FIRMWARE CAN DESTROY A PHONE
    31
    Frequently Asked Questions:

    Can I restore Factory Firmware if my Bootloader is locked?
    Yes. However attempting to downgrade to an older version of Android may fail - 'Preflash validation' error. Even with an unlocked Bootloader, downgrading cannot be guaranteed. It's also important to be aware that flashing the wrong Bootloader (bootloader.img) for your model can have serious consequences. Always establish your model of Moto G before flashing.

    I get a 'Preflash validation' error when flashing a Firmware Image
    The Firmware Image you are trying to flash is too old. You can only flash a firmware image that matches, or is newer than the most recent system version you have had on your phone. However the former scenario can also sometimes return the error. In which case, your options are to wait for an even newer firmware image or unlock Bootloader and flash a ROM zip.

    After flashing Firmware Image files phone gets stuck during boot-up | will not load Android?
    Check you are naming the files correctly, and make sure you are flashing all of the 'sparsechunk' files - not just those mentioned in the tutorial. The 'sparsechunk' commands listed there are not to be copied exactly, different firmware images may have different files.

    How to flash Radio Firmware only?
    Use the following fastboot commands:
    fastboot flash modem NON-HLOS.bin
    fastboot erase modemst1
    fastboot erase modemst2
    fastboot flash fsg fsg.mbn​

    How do I downgrade to an older Firmware?
    Downgrading carries risks, and may result in constant nagging notifications to update Android. Decide carefully if this is really what you want. With earlier generations of Moto G flashing bootloader.img and gpt.bin has resulted in a hard-brick. Avoid flashing these files if you are trying to downgrade. The safer option is to find a custom Stock ROM with OTA Updates disabled.

    Fastboot in Linux is not working?
    In Linux, root access is required for Fastboot and/or ADB to work.
    sudo fastboot devices​
    20
    Factory data reset via Stock Recovery:
    (1) Flash via fastboot stock recovery.img (found in firmware image zip)
    (2) Turn your phone off.
    (3) Press and hold Volume DOWN + POWER.
    (4) In recovery menu press Volume down twice.
    (5) Press power. You will see a red exclamation mark.
    (6) Hold power down, then tap Volume UP.
    (7) Go to Wipe data / Factory reset and press power button.
    (8) Scroll to Yes - delete all user data and press power.​
    4
    Yes and no.
    I mean reflashing same firmware.
    If I reflash same firmware, but only system partition (or all files), I think it could work (to unroot) without erasing anything.
    In nexus 7, reflashing same firmware without erasing user data is the right way to unroot.

    Three days ago I upgraded from 5.1 to 6.0 without performing 'Factory data reset' and Android boots ok
    With Moto G (3rd Gen) in particular - not doing a 'factory data reset' has prevented Android booting for many people. It's also my experience with Moto G generally that not erasing userdata can introduce a wide range of issues, from very minor to very serious. I am now of the opinion that if you have not done a 'Factory data reset' in Android and erased userdata during fastboot flashing - you have not flashed Android properly. For best performance / experience, do what I say.
    3
    @lost101, do you think the downgrade could result if we flash only gtp.bin and bootloader (it will flash the old bootloader), reboot to bootloader (the old one now) and then flash the other partitions?
    Sorry if this is a stupid question.
    The last thing you should ever do is touch the Bootloader on a device. It's completely unnecessary and stupidly dangerous.

    These are the only commands required:
    fastboot flash boot boot.img
    fastboot flash system system.img_sparsechunk.0
    fastboot flash system system.img_sparsechunk.1
    fastboot flash system system.img_sparsechunk.2
    fastboot flash system system.img_sparsechunk.3
    fastboot flash system system.img_sparsechunk.4
    fastboot flash system system.img_sparsechunk.5
    fastboot flash modem NON-HLOS.bin
    fastboot erase modemst1
    fastboot erase modemst2
    fastboot flash fsg fsg.mbn
    fastboot erase cache
    fastboot erase userdata
    fastboot reboot​

    If not booting, add the following command at the beginning of list:
    fastboot flash partition gpt.bin​