[One (M8) Q&A, Help & Troubleshooting] matti68:
htc m8 bootloop how to solve ?

Have a HTC M8 that stucks in bootlop, here the details

version: 0.5

version-bootloader: 3.19.0.0000

version-baseband: 1.25.21331147A1.06G

version-cpld: None

version-microp: None

version-main: 4.19.166.2

version-misc: PVT SHIP S-ON

product: m8_ul

platform: hTCBmsm8974

modelid: 0P6B10000

I found the correct firmware and flashed it, Flash seems to be successful I see errors concerning sbl1

fastboot flash zip firmware.zip

At the end I see

OKAY [ 20.115s]

finished. total time: 23.271s

I see signature verifly failed sbl1

(bootloader) start image[sbl1] unzipping & flushing...

(bootloader) [RUU]UZ,sbl1,0

(bootloader) [RUU]UZ,sbl1,100

(bootloader) signature checking...

(bootloader) verified fail

(bootloader) ..... Bypassed

(bootloader) current_image_number=4

Here the complete output

< waiting for device >

target reported max download size of 1826418688 bytes

sending 'zip' (52102 KB)...

OKAY [ 3.125s]

writing 'zip'...

(bootloader) adopting the signature contained in this image...

(bootloader) signature checking...

(bootloader) zip header checking...

(bootloader) zip info parsing...

(bootloader) checking model ID...

(bootloader) checking custom ID...

(bootloader) checking main version...

(bootloader) checking hboot version...

(bootloader) total_image_number=12

(bootloader) start image[adsp] unzipping & flushing...

(bootloader) [RUU]UZ,adsp,0

(bootloader) [RUU]UZ,adsp,11

(bootloader) [RUU]UZ,adsp,21

(bootloader) [RUU]UZ,adsp,33

(bootloader) [RUU]UZ,adsp,43

(bootloader) [RUU]UZ,adsp,55

(bootloader) [RUU]UZ,adsp,66

(bootloader) [RUU]UZ,adsp,76

(bootloader) [RUU]UZ,adsp,88

(bootloader) [RUU]UZ,adsp,98

(bootloader) [RUU]UZ,adsp,100

(bootloader) [RUU]WP,adsp,0

(bootloader) [RUU]WP,adsp,100

(bootloader) ...... Successful

(bootloader) current_image_number=0

(bootloader) start image[boot] unzipping & flushing...

(bootloader) [RUU]UZ,boot,0

(bootloader) [RUU]UZ,boot,11

(bootloader) [RUU]UZ,boot,23

(bootloader) [RUU]UZ,boot,35

(bootloader) [RUU]UZ,boot,48

(bootloader) [RUU]UZ,boot,59

(bootloader) [RUU]UZ,boot,70

(bootloader) [RUU]UZ,boot,81

(bootloader) [RUU]UZ,boot,95

(bootloader) [RUU]UZ,boot,100

(bootloader) [RUU]WP,boot,0

(bootloader) [RUU]WP,boot,99

(bootloader) [RUU]WP,boot,100

(bootloader) ...... Successful

(bootloader) current_image_number=1

(bootloader) start image[recovery] unzipping & flushing...

(bootloader) [RUU]UZ,recovery,0

(bootloader) [RUU]UZ,recovery,6

(bootloader) [RUU]UZ,recovery,12

(bootloader) [RUU]UZ,recovery,19

(bootloader) [RUU]UZ,recovery,26

(bootloader) [RUU]UZ,recovery,32

(bootloader) [RUU]UZ,recovery,38

(bootloader) [RUU]UZ,recovery,52

(bootloader) [RUU]UZ,recovery,57

(bootloader) [RUU]UZ,recovery,63

(bootloader) [RUU]UZ,recovery,70

(bootloader) [RUU]UZ,recovery,77

(bootloader) [RUU]UZ,recovery,83

(bootloader) [RUU]UZ,recovery,89

(bootloader) [RUU]UZ,recovery,97

(bootloader) [RUU]UZ,recovery,100

(bootloader) [RUU]WP,recovery,0

(bootloader) [RUU]WP,recovery,99

(bootloader) [RUU]WP,recovery,100

(bootloader) ...... Successful

(bootloader) current_image_number=2

(bootloader) start image[rpm] unzipping & flushing...

(bootloader) [RUU]UZ,rpm,0

(bootloader) [RUU]UZ,rpm,100

(bootloader) signature checking...

(bootloader) ...... Successful

(bootloader) current_image_number=3

(bootloader) start image[sbl1] unzipping & flushing...

(bootloader) [RUU]UZ,sbl1,0

(bootloader) [RUU]UZ,sbl1,100

(bootloader) signature checking...

(bootloader) verified fail

(bootloader) ..... Bypassed

(bootloader) current_image_number=4

(bootloader) start image[sbl1] unzipping & flushing...

(bootloader) [RUU]UZ,sbl1,0

(bootloader) [RUU]UZ,sbl1,100

(bootloader) signature checking...

(bootloader) verified fail

(bootloader) ..... Bypassed

(bootloader) current_image_number=5

(bootloader) start image[sbl1] unzipping & flushing...

(bootloader) [RUU]UZ,sbl1,0

(bootloader) [RUU]UZ,sbl1,100

(bootloader) signature checking...

(bootloader) ...... Successful

(bootloader) current_image_number=6

(bootloader) start image[sbl1] unzipping & flushing...

(bootloader) [RUU]UZ,sbl1,0

(bootloader) [RUU]UZ,sbl1,100

(bootloader) signature checking...

(bootloader) verified fail

(bootloader) ..... Bypassed

(bootloader) current_image_number=7

(bootloader) start image[sensor_hub] unzipping & flushing...

(bootloader) [RUU]UZ,sensor_hub,0

(bootloader) [RUU]UZ,sensor_hub,100

(bootloader) ...... Successful

(bootloader) current_image_number=8

(bootloader) start image[wcnss] unzipping & flushing...

(bootloader) [RUU]UZ,wcnss,0

(bootloader) [RUU]UZ,wcnss,24

(bootloader) [RUU]UZ,wcnss,45

(bootloader) [RUU]UZ,wcnss,68

(bootloader) [RUU]UZ,wcnss,96

(bootloader) [RUU]UZ,wcnss,100

(bootloader) [RUU]WP,wcnss,0

(bootloader) [RUU]WP,wcnss,100

(bootloader) ...... Successful

(bootloader) current_image_number=9

(bootloader) start image[radio] unzipping & flushing...

(bootloader) [RUU]UZ,radio,0

(bootloader) [RUU]UZ,radio,11

(bootloader) [RUU]UZ,radio,18

(bootloader) [RUU]UZ,radio,27

(bootloader) [RUU]UZ,radio,36

(bootloader) [RUU]UZ,radio,44

(bootloader) [RUU]UZ,radio,49

(bootloader) [RUU]UZ,radio,54

(bootloader) [RUU]UZ,radio,62

(bootloader) [RUU]UZ,radio,67

(bootloader) [RUU]UZ,radio,76

(bootloader) [RUU]UZ,radio,81

(bootloader) [RUU]UZ,radio,89

(bootloader) [RUU]UZ,radio,94

(bootloader) [RUU]UZ,radio,100

(bootloader) trying to rename MBA

(bootloader) [RUU]WP,radio,0

(bootloader) [RUU]WP,radio,35

(bootloader) [RUU]WP,radio,71

(bootloader) [RUU]WP,radio,100

(bootloader) ...... Successful

(bootloader) current_image_number=10

(bootloader) start image[rcdata] unzipping & flushing...

(bootloader) [RUU]UZ,rcdata,0

(bootloader) [RUU]WP,rcdata,0

(bootloader) ...... Successful

(bootloader) current_image_number=11

OKAY [ 20.115s]

finished. total time: 23.271s

When I extract the boot.img from firmware.zip and only Flash the boot.img I get following error signature verify fail

fastboot flash boot boot.img

target reported max download size of 1826418688 bytes

sending 'boot' (8782 KB)...

OKAY [ 1.031s]

writing 'boot'...

(bootloader) signature checking...

FAILED (remote: 12 signature verify fail)

finished. total time: 1.375s

Calculating the Image CRC the following Output, is 0x0 for sb2 and sb3 correct ?

rpm: 0xD0AD2083

sbl1: 0xE3DB0B9A

sbl2: 0x0

sbl3: 0x0

tz: 0x7A5540112

radio: 0x53CED4FB

hboot: 0x5E7000B5

boot:: 0x83481B7F

recovery: 0xA92185E2

system: 0xF7612432

Can you give me a hint how to solve the problem ?

Any idea how or where to get RUU Image for version 4.19.166.2 ?

Is it possible to downgrade the Firmware, but how to I know what are previous version to 4 .19.166.2 ?

Is there a way to unlock the device manually (APP can't be used in this Status) and to install a custom ROM ?

Your help is really appreciated, thx.