Mitsubishi Electric PUMY-P112VKM4 Technical & Service Manual page 53

Check code
0403
(Ed)
Abnormal points and detection methods
If serial communication between the outdoor multi controller circuit board
and outdoor power circuit board is defective.
●Diagnosis of defects
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 multi
controller circuit board and power circuit board.
Are they connected normally?
OCH673C
Serial communication error
Diagnosis
Yes
Causes and checkpoints
Wire breakage or contact failure of connector CN2 or
CN4
Malfunction of communication circuit to power circuit
board on outdoor multi controller circuit board
Malfunction of communication circuit on outdoor
power circuit board
Connect the CN2 and CN4 properly.
No Replace them in case of breakage.
The communication circuit of either the
outdoor multi controller circuit board or
power circuit board is defective.
If unable to identify the defective circuit;
Replace the outdoor multi controller
circuit board if it does not recover.
Replace the outdoor power circuit board.
53
Remedy