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10 Troubleshooting
10.2 Diagnostics on the PLC Main Unit
108
FX3U-CF-ADP User's Manual
10.2.3 ERROR(ERR) LED [on/flashing/off]
The table below describes details for the LED statuses.
Status PLC Status Error corrective action
ON
A watchdog timer error may have occurred,
or the hardware of the PLC may be
damaged.
1) Stop the PLC, and turn the power ON again.
If the ERROR(ERR) LED goes out, a watchdog timer error may have
occurred. Adopt any of the following measures:
- Review the program.
Set the maximum value (D8012) lower than the watchdog timer value.
- Check that the input used for input interrupt or pulse catch is not being
abnormally turned ON and OFF in one scan.
- Check that the frequency of the pulse (duty 50%) input to the high-
speed counter is not exceeding the specified range.
- Add WDT instructions.
Add some WDT instructions to the program, and reset the watchdog
timer several times in one scan.
- Change the watchdog timer value.
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 the power to it from another power source.
If the ERROR(ERR) LED goes out, noise may have affected the PLC.
Adopt the following measures:
- Check the ground wiring, and re-examine the wiring route and
installation location.
- Fit a noise filter onto the power supply line.
3) If the ERROR(ERR) LED does not go out even after measures in 1) and
2) are adopted, consult a Mitsubishi Electric distributor.
Flicker
One of the following errors has occurred on
the PLC:
• Parameter error
•Syntax error
• Ladder error
Perform PLC diagnosis and program check with the programming tool.
OFF No errors to 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, parallel link/communication error, or operation error may have
occurred.