Mitsubishi Electric CITY MULTI PUHY-P200YEM-A Service Handbook page 121

(1) Mechanical
Checking code Meaning, detecting method
0403 Serial If serial transmission cannot be
transmission established between the MAIN and
abnormality INV boards.
Cause
1) Wiring is defective.
2) Switches are set wrong on the INV
board.
3) The fuse (F01) on the INV board
is defective.
4) The circuit board is defective.
- 120 -
Checking method & Countermeasure
Check 1, the connections, 2, contact
at the connectors and 3, for broken
wires in the following wiring.
CNRS2 - CNRS3
CNAC2 - TB1B
SW1-4 on the INV board should be
OFF.
If the fuse is melted, (if the resistance
between the both ends of fuse is ∞),
replace the fuse.
If none of the items in 1) to 3) is appli-
cable, and if the trouble reappears even
after the power is switched on again,
replace the circuit board by the follow-
ing procedure (when replacing the cir-
cuit board, be sure to connect all the
connectors, ground wires, etc. se-
curely).
1 If serial transmission is restored af-
ter the INV board is replaced, then
the INV board is defective.
2 If serial transmission is not restored,
reinstall the INV board and replace
the MAIN board. If serial transmis-
sion is restored, the MAIN board is
defective.
3 If serial transmission is not restored
by 1 and 2 above, replace both
boards.