Serial Communication Error; 0403; Diagnosis Of Defects - Mitsubishi Electric PUMY-P250YBM Technical & Service Manual

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
controller board and power board.
Are they connected normally?
Check the wiring.
Are they connected normally?
OCH760

Serial communication error

Diagnosis
Yes
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 the case of breakage.
Connect the wiring properly.
No
Replace them in the case of 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
does not recover,
Replace the outdoor power board.
42
Remedy