Mitsubishi Electric Melsec QJ71LP21 Reference Manual page 403

8 TROUBLESHOOTING
8.2 Troubleshooting
Yes
E
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Check the programmable controller CPU for an error before starting the
troubleshooting of the network module and network.
If the RUN LED of the programmable controller CPU is off/flickering or the ERR. LED is
on, identify the error that occurred in the programmable controller CPU, and take
corrective action.
(1) Check that the host has joined the network.
Start the troubleshooting of the host by monitoring the status of the host. First,
check whether or not the host has joined the network.
This is important because it is not possible to monitor the status of other stations
and to perform troubleshooting on other stations unless the host has joined the
network.
The troubleshooting flowchart shown below explains the sequence from checking
an error to enabling a baton pass (in order to join the network).
Start
Is the "T.PASS"
LED of the
host lit?
No
Is the "RUN" LED lit? No
Yes
to the power supply
Is the "ERR." LED lit?
Execute offline tests.
1) Hardware test
2) Self-loopback test
3) Internal self-loopback test
No
<Corrective action>
Replace the network module.
Correct the error according
to the content of the error
code stored in SW0048.
POINT
If the T. PASS LED turns on and off and looks unstable, refer to the following.
<Cause>
The line status is assumed to be unstable.
<Troubleshooting>
1) Check the connector for loose connection and the cable for a break.
2) Check that the cable used conforms to the specifications.
3) Check that the overall length and station-to-station distance are within
specifications. (Refer to Section 4.6 Cable Connection.).
Yes
The host's baton pass
is normal.
End
The host is
in the normal status.
Is the
power supplied
module?
YES
Test results? OK
NG
<Cause>
Possible module watchdog
timer error
<Corrective action>
Check :
1) Verify the base installation.
2) Reset the CPU.
3) Replace the module.
4) Whether or not the host's
I/O slot is assigned to a
"Empty area."
MELSEC-Q
No
<Cause>
The power is not being supplied.
Or, the overcurrent protection is
active.
<Corrective action>
1) Verify the power supply status.
2) Check that the total current
consumption of the module
installed on the base unit
does not exceed the rated
output current of the power
supply module used.
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