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MELSEC-Q
11 TROUBLESHOOTING
Occurrence
Error
Code
Error Name
Description
Lit LED
Corrective Action
1) 2) 3) 4) 5)
7393
H
Data unit error
• The contents of the data unit
in the received request
message are incorrect.
• The size of the received
request message is smaller
than the minimum size or
greater than the maximum
size required for the relevant
function code.
COM.ERR.
Review the contents of the
request message on the master
side from which the request
message was sent.
7394
H
Online change
error
A write request message was
received in an online change
disable status.
COM.ERR.
• While online change is disabled,
do not issue a write request
message.
• Turn ON b2 of the intelligent
function module switch 2
(communication condition
setting) to enable the online
change.
7395
H
MBAP header
error
The contents of the MBAP
header in the received request
message are incorrect.
COM.ERR.
Review the contents of the
request message on the master
side from which the request
message was sent.
7396
H
Slave function
busy
The QJ71MT91 received
request messages that exceed
the number of simultaneously
receivable request messages
(64).
COM.ERR.
Retry after a little while on the
master side from which the
request message was sent.
739C
H
to
739E
H
System error
The OS of the QJ71MT91
detected error.
COM.ERR.
Counter the problem in the
following procedure.
• Check whether or not the
QJ71MT91, power supply
module and CPU module are
mounted correctly on the base
unit.
• Check whether or not the
operating environment of the
system is within the range of
general specifications of the
CPU module.
• Check whether the power
capacity is sufficient or not.
• Check the QJ71MT91, CPU
module and base unit to see if
the hardware is normal
according to the manual of each
module.
If the module is faulty, please
contact your local Mitsubishi
service center or representative
for repair.
• If the problem cannot be
resolved in the above steps,
please consult your local
Mitsubishi service center or
representative, explaining a
detailed description of the
problem.
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