LG Multi V CRUN Series Service Manual page 242

Self-diagnosis function
Fault diagnosis and Trouble shooting guide
Display
Title
code
Transmission
error from main
57
PCB to inverter
PCB in the
outdoor unit
Trouble shooting Flow
242 Trouble Shooting Guide
Meaning
In the case that inverter
PCB can not receive any
signal
from main PCB
successively for 20
seconds
Is the transmission
line connection /
Connector normal?
Yes
Is the transmission
circuit of main PCB
normal?
Yes
Check and replace the
inverter PCB
Cause of error
• The connector for transmission disconnected
• The transmission line is misconnected or shorted
• Transmission circuit of main PCB is abnormal
• Transmission circuit of inverter PCB is abnormal
No
Repair the connection /
connector
No
Check and Replace the
main PCB