[G2 and Desire Z Q&A, Help & Troubleshooting] akamarukiba:
I know this is a common problem, and this is the fourth time this happens to my phone, but since last summer I have no warranty left to keep my phone alive.

My phone has too many unexpected random reboots, since four days they are increasing heavily, the three other times this happened HTC replaced the mainboard. I am using Flinnys CM 11 Alpha 3 since its release, I know it is unstable, but these kinds of problems are new and reflashing this rom or CM 10.1 did not helped.

I searched a bit and I found out nothing positive, but are there chances JTag can fix this problem? I haven't detected any mmc error yet, and I want to keep this phone alive, but it isn't worth to buy a new mainboard. My phone is S-Off with Engineering HBoot.

I do not want to buy JTag cables/acessoires without a chance it could fix that, since I would need to import something to Germany and I think my phone is hardware damaged, hoping I am wrong.

In recovery mode I checked MMC: adb shell dmesg | grep mmc

<5>[ 0.000000] Kernel command line: board_vision.disable_uart2=0 board_vision.usb_h2w_sw=0 board_vision.disable_sdcard=0 diag.enabled=0 board_vision.debug_uart=0 smisize=0 userdata_sel=0 androidboot.emmc=true androidboot.baseband=26.13.04.19_M androidboot.cid=HTC__102 androidboot.batt_poweron=good_battery androidboot.carrier=HTC-GER androidboot.mid=PC1011000 androidboot.keycaps=qwerty androidboot.mode=recovery androidboot.serialno=[I]*removed*[/I] androidboot.bootloader=0.84.2000 no_console_suspend=1 console=null
<6>[ 7.228332] vision: vision_init_mmc
<3>[ 8.179473] mmc0: No card detect facilities available
<6>[ 8.180084] mmc0: Qualcomm MSM SDCC at 0x00000000a0500000 irq 98,0 dma 7
<6>[ 8.180328] mmc0: Platform slot type: MMC
<6>[ 8.180480] mmc0: 4 bit data mode disabled
<6>[ 8.180603] mmc0: 8 bit data mode enabled
<6>[ 8.180847] mmc0: MMC clock 144000 -> 50000000 Hz, PCLK 96000000 Hz
<6>[ 8.180999] mmc0: Slot eject status = 0
<6>[ 8.181121] mmc0: Power save feature enable = 1
<6>[ 8.181274] mmc0: DM non-cached buffer at ff00d000, dma_addr 0x0f518000
<6>[ 8.181396] mmc0: DM cmd busaddr 0x0f518000, cmdptr busaddr 0x0f518300
<6>[ 8.182434] mmc1: Qualcomm MSM SDCC at 0x00000000a3000000 irq 96,0 dma 8
<6>[ 8.182678] mmc1: Platform slot type: N/A
<6>[ 8.182800] mmc1: 4 bit data mode enabled
<6>[ 8.182952] mmc1: 8 bit data mode disabled
<6>[ 8.183197] mmc1: MMC clock 144000 -> 50000000 Hz, PCLK 96000000 Hz
<6>[ 8.183349] mmc1: Slot eject status = 1
<6>[ 8.183593] mmc1: Power save feature enable = 1
<6>[ 8.183715] mmc1: DM non-cached buffer at ff00e000, dma_addr 0x0f519000
<6>[ 8.183990] mmc1: DM cmd busaddr 0x0f519000, cmdptr busaddr 0x0f519300
<6>[ 8.185363] mmc2: Qualcomm MSM SDCC at 0x00000000a3100000 irq 100,0 dma 8
<6>[ 8.185516] mmc2: Platform slot type: SD
<6>[ 8.185760] mmc2: 4 bit data mode enabled
<6>[ 8.185882] mmc2: 8 bit data mode disabled
<6>[ 8.186035] mmc2: MMC clock 144000 -> 50000000 Hz, PCLK 96000000 Hz
<6>[ 8.186279] mmc2: Slot eject status = 0
<6>[ 8.186401] mmc2: Power save feature enable = 1
<6>[ 8.186676] mmc2: DM non-cached buffer at ff00f000, dma_addr 0x0f51b000
<6>[ 8.186798] mmc2: DM cmd busaddr 0x0f51b000, cmdptr busaddr 0x0f51b300
<6>[ 8.187072] mmc2: Polling status mode enabled
<6>[ 8.345214] mmc0: new high speed MMC card at address 0001
<6>[ 8.347290] mmcblk0: mmc0:0001 M4G2DE 2.10 GiB
<6>[ 8.348724] mmcblk0: p1 p2 p3 p4 < p5
<4>[ 8.635314] mmc2: high speed mode max_dtr = 50000000
<4>[ 8.635650] mmc2: host does not support reading read-only switch. assuming write-enable.
<6>[ 8.635894] mmc2: new high speed SDHC card at address e624
<6>[ 8.644683] mmcblk1: mmc2:e624 SU08G 7.40 GiB
<6>[ 8.645538] mmcblk1: p1
<6>[ 10.405792] EXT4-fs (mmcblk0p27): mounted filesystem with ordered data mode. Opts:
<3>[ 10.565460] EXT3-fs (mmcblk0p25): error: couldn't mount because of unsupported optional features (40)
<3>[ 10.567626] EXT2-fs (mmcblk0p25): error: couldn't mount because of unsupported optional features (40)
<6>[ 10.618499] EXT4-fs (mmcblk0p25): mounted filesystem with ordered data mode. Opts: (null)
<6>[ 19.993225] EXT4-fs (mmcblk0p25): mounted filesystem with ordered data mode. Opts:
<6>[ 20.125244] EXT4-fs (mmcblk0p26): mounted filesystem with ordered data mode. Opts:
<3>[ 20.269561] EXT4-fs (mmcblk1p1): VFS: Can't find ext4 filesystem
<3>[ 20.274169] EXT4-fs (mmcblk1): VFS: Can't find ext4 filesystem