Serial Commucication Error; Diagnosis Of Defectives - Mitsubishi PUMY-P60NKMU Technical & Service Manual

Check code
0403
Abnormal points and detection methods
Abnormal if serial communication between the outdoor controller board
and outdoor power board is defective.
●Diagnosis of defectives
Make sure to turn the power OFF before connecting/disconnecting any connectors, or replacing boards.
Check the connection of the communication
line (CN2 and CN4) between the outdoor
controller board and power board.
Are they connected normally?
OCH502C

Serial commucication error

Diagnosis
No
Yes
Causes and check points
Wire breakage or contact failure of connector CN2 or
CN4
Malfunction of power board communication circuit on
outdoor controller board
Malfunction of communication circuit on outdoor
power board
Connect the CN2 and CN4 properly.
Replace them in case of a breakage.
The communication circuit of either the
outdoor controller board or power board is
defective.
If unable to identify the defective circuit;
Replace the outdoor controller board if it
doesn't recover,
Replace the outdoor power board
33 33
Remedy