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FX3S/FX3G/FX3GC/FX3U/FX3UC Series
Programming Manual - Basic & Applied Instruction Edition
38 Error Check Method and Error Code List
38.1 States and Colors of LEDs PLC Operation Status
38.1.5 ERROR (ERR) LED [lit, flickering or unlit]
38.1.6 L RUN LED [FX3UC-32MT-LT(-2)]
*1. FX3UC-32MT-LT only.
LED status PLC status Action
Lit
A watchdog timer error has occurred, or
the hardware of the PLC may be
damaged.
1) Change the PLC mode to STOP, and turn ON the PLC power
again.
When the ERROR (ERR) LED is off, a watchdog timer error
occurred. Take one of the following actions:
- Review the program, and make sure that the maximum
value (D8012) of the scan time is not larger than the set
value (D8000) of the watchdog timer.
- Make sure that an input used for input interrupt or pulse
catch does not abnormally turn ON and OFF several times
in one scan time.
- Make sure that the frequency of the pulse (duty: 50%) input
to a high-speed counter is within the specifications range.
- Adding a WDT instruction
Use two or more WDT instructions in a program so that the
watchdog timer is reset several times in one scan time.
- Change the set value of the watchdog timer
Change the set value (D8000) of the watchdog timer in a
program so that it is larger than the maximum value (D8012)
of the scan time.
2) Remove the PLC, and connect another power supply to the
PLC.
If the ERROR (ERR) LED is off, the cause of the error may be
noise. Examine the following action:
- Check the wiring for grounding, and then review the wiring
route and installation location.
- Add a noise filter in the power line.
3) If the ERROR (ERR) LED is not off even after the step 1) or 2),
consult a Mitsubishi Electric representative.
Flickering
One of the following errors occur in PLC:
• Parameter error
• Syntax error
• Circuit error
Execute PLC diagnostics and program check by programming tool.
For instructions, refer to Section 38.4.
Unlit Error which stops PLC has not occurred.
If PLC operation is a failure, execute the PLC diagnostics or
program check by programming tool.
An I/O configuration error, serial communication error, or operation
error may occur.
Mode LED status PLC status Action
ONLINE
Lit Data link is executing ⎯
Unlit Data link is stopped • Take action according to the L ERR LED status.
CONFIG
*1
Lit Data link is executing ⎯
Unlit Data link is stopped • Take action according to the L ERR LED status.
TEST
Lit
The self-loopback test is
normally finished.
⎯
Unlit
The self-loopback test is
abnormally finished.
(This LED is off
while the self-loopback test
is executing.)
• Make sure that the power is correctly supplied to the PLC.
• If the L RUN LED is not off even after the above check, consult a
Mitsubishi Electric representative.