Transmission Bus Busy Error - Mitsubishi Electric PUMY-P200YKM Technical & Service Manual

Check code
6603
Abnormal points and detection methods
Over error by collision
Abnormal if no-transmission status caused by a transmitting data
collision is consecutive for 8 to 10minutes.
Abnormal if a status, that data is not allowed on the transmission line
because of noise and such, is consecutive for 8 to 10 minutes
●Diagnosis of defectives
Make sure to turn the power OFF before connecting/disconnecting any connectors, or replacing boards.
Check whether the transmission line to the indoor unit,
Fresh Master, Lossnay or remote controller is miswired
to the terminal block (TB7) on outdoor unit or not.
Is the transmission line miswired?
Check whether the transmission line with the other refrigerant
system of the indoor unit, Fresh Master or Lossnay is miswired
to the terminal block (TB3) on outdoor unit or not.
Is the transmission line miswired?
Turn the power back ON.
Does it operate normally?
OCH575

Transmission bus BUSY error

Diagnosis
(miswired)
(Not miswired)
No
(miswired)
(Not miswired)
Yes
Yes
Causes and check points
The transmission processor is unable to transmit due
to a short-cycle voltage such as noise is mixed on
the transmission line.
The transmission processor is unable to transmit due
to an increase of transmission data amount caused
by a miswiring of the terminal block (transmission
line) (TB3) and the terminal block (centralized control
line) (TB7) on the outdoor unit.
The share on transmission line becomes high due
to a mixed transmission caused by a malfunction
of repeater on the outdoor unit, which is a function
to connect/disconnect transmission from/to control
system and centralized control system.
Correct the wiring, then turn the power
Yes
back ON.
Correct the wiring, then turn the power
No
back ON.
Replace the indoor/outdoor controller
No
board.
There is no abnormality on the AC unit.
It might be caused by an external noise, so check
the transmission line to remove the factor(s).
74
Remedy