[General Questions and Answers] peido:
I know a few years have passed, but I had a similar problem today and it took me the whole day to find a solution. Might help somebody else in the future. My log presented the same error code as thenugpot's log.

I was trying to flash a LG C660 (to unbrick it), with the phone in Emergency Mode I connected it to the USB cable and started KDZ UPDATER. KDZ UPDATER would detect the phone and start the process, but after a few moments the phone would reboot and stay forever in the LG logo, after about 5 minutes the process would fail.

My log was:

[22:18:31:625] : =============================================

[22:18:31:625] : Log is started on 28.12.2015, at 22:18:31:625,

executable: E:\LG Optimus Pro (C660)\KDZ_FW_UPD.exe (ProcID: 0x000003d4),

compile time : Jan 19 2012 09:29:39

[22:18:31:625] : Version :

[22:18:31:625] : Get Usb Port

[22:18:31:629] : rsi.strFriendlyName=Porta de comunicações (COM1)

[22:18:31:629] : Remove Porta de comunicações (COM1)

[22:18:31:629] : rsi.strFriendlyName=LGE Android Platform USB Serial Port (COM4)

[22:18:31:629] : FriendlyNameList[iii].szFriendlyName=LGE Android Platform USB Serial Port

[22:18:31:629] : WM_COPYDATA ¸Þ½ÃÁö º¸³¿ 1 - COM4

[22:18:31:629] : Port = COM4

[22:18:31:632] : UNKNOWN : Req(12) -> Rsp(13)

[22:18:31:634] : UNKNOWN : Req(12) -> Rsp(13)

[22:18:31:636] : UNKNOWN : Req(12) -> Rsp(13)

[22:18:31:636] : >> DIAG_STATUS_F FAILED

[22:18:31:642] : >>Get Model Name [DIAG_VERNO_F]

[22:18:31:644] : BAD CONN MODE : Req(0) -> Rsp(3)

[22:18:31:646] : BAD CONN MODE : Req(0) -> Rsp(3)

[22:18:31:648] : BAD CONN MODE : Req(0) -> Rsp(3)

[22:18:31:650] : BAD CONN MODE : Req(0) -> Rsp(3)

[22:18:31:652] : BAD CONN MODE : Req(0) -> Rsp(3)

[22:18:31:654] : BAD CONN MODE : Req(0) -> Rsp(3)

[22:18:31:654] : FAIL (No Phone)

[22:18:31:654] : GetModelName() Operation Failed Check Diag CMD

[22:18:31:654] : EMERGENCY Booting Mode

[22:18:31:654] : >>Get Model Name in Emergency Mode [DLOAD_VERREQ_F]

[22:18:31:656] : BS/C660/7Dmg

[22:18:31:656] : WM_COPYDATA ¸Þ½ÃÁö º¸³¿ 0 - C660

[22:18:31:656] : _Reset_N_Close bFirst = 3

[22:18:31:656] : ¸Þ½ÃÁö º¸³¿ TYPE_WPARAM_RESET_THE_PHONE_1ST 8

[22:18:31:656] : [COM4] Reset [DLOAD]

[22:18:31:656] : WM_COPYDATA ¸Þ½ÃÁö º¸³¿ 3 - RESET

[22:18:31:957] : DIAG_DLOAD_F DLOAD_RESET_F do not wait for response

[22:18:32:257] : WM_COPYDATA ¸Þ½ÃÁö º¸³¿ 3 - Close Port

[22:18:32:257] : Close Port<<

[22:25:12:257] : OPEN_PORT_FAIL

[22:25:12:257] : TYPE_WPARAM_UPGRADE_ERROR

[22:25:12:257] : ¸Þ½ÃÁö º¸³¿ - TYPE_WPARAM_UPGRADE_ERROR Error Code = 6

[22:25:12:289] : Log finished

To bypass the problem I did the following: Start phone in Emergency Mode, Connect phone to PC using USB cable, Start KDZ UPDATER and start process, has soon has the phone reboots and stays forever in the LG logo I would disconnect the USB cable, remove the battery, insert the battery, restart the phone in Emergency Mode, connect the USB cable. As soon as I did this, KDZ UPDATER continued the process and after a few minutes everything ended successfully.

Thanks to Claudiow in another forum for finding the solution to this problem with a LG P698, and to raimundez from that same forum.