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14 Test Operation, Adjustment, Maintenance and Troubleshooting
14.5 Troubleshooting with LEDs
211
FX3G Series Programmable Controllers
User's Manual - Hardware Edition
11
High-Speed
Counters
12
Output Wiring
13
Wiring for
Various Uses
14
Test Run,
Maintenance,
Troubleshooting
15
Input/Output
Powered
Extension Units
16
Input/Output
Extension
Blocks
17
Extension
Power Supply
Unit
18
Other Extension
Units and
Options
19
Display Module
20
Terminal Block
14.5.3 ERR LED [on/flashing/off]
State of
LED
State of PLC Remedies
On
A watchdog timer error may have occurred, or
the hardware of the PLC may be damaged.
1) Stop the PLC, and re-apply power.
If ERR LED goes off, a watchdog timer error may have occurred.
Take any of the following measures.
- Review the program.
The maximum value (D8012) of the scan time should not exceed
the setting (D8000) of the watchdog timer.
- Check that the input used for input interruption or pulse catch is
not being abnormally turned on and off in one scan.
- Check that the frequency of the pulse (duty of 50%) input to the
high-speed counter does not exceed the specified range.
- Add the WDT instructions.
Add some WDT instructions to the program, and reset the
watchdog timer several times in one scan.
- Change the setting of the watchdog timer.
Change the watchdog timer setting (D8000) in the program so
that the setting is larger than the maximum value of the scan time
(D8012).
2) Remove the PLC and supply power to it from another power supply
on a desk.
If the ERR LED goes off, noise may have affected the PLC.
Take the following measures.
- Check the ground wiring, and reexamine the wiring route and
installation location.
- Fit a noise filter onto the power supply line.
3) If the ERR LED does not go off even after the measures stated in
(1) and (2) are taken, consult your local Mitsubishi Electric
representative.
Flashing
One of the following errors has occurred in the
PLC.
• Parameter error
• Syntax error
• Ladder error
Perform PLC diagnosis and program check with the programming tool.
For the remedies, refer to 14.6 Judgment by Error Codes and
Representation of Error Codes.
Off No errors that stop the PLC have occurred.
If the operations of the PLC are abnormal, perform PLC diagnosis and
program check with the programming tool.
An I/O error, Comms error or Runtime error may have occurred.