LG 42PC55 Service Manual page 26

(5) In the case of becomes unusual display from Component, RGB mode
Is theR,G,B input and H,V
Sync of the J1100 normal?
Yes
Same as Block A
(6) In the case of becomes unusual display from HDMI mode
Is the HDMI002(IC1004)
normal?
Yes
Same as Block A
(7) In the case of becomes unusual display from SCART1 mode
Is the Video input of A/V
Jack(J1200) normal?
Yes
Same as Block A
(8) In the case of becomes unusual display from SCART2 mode
Is the Video input of A/V
Jack(J1201) normal?
Yes
Same as Block A
No
Check the input source
No
Is the Input and Output signal,IIC
Communication normal?
No
Check the input source
No
Check the input source
No
Replace the IC.