Mitsubishi Electric MELSEC iQ-R Series - Troubleshooting with LED Indicators; LED Status of the CPU Module

33 TROUBLESHOOTING PROCEDURE
33.1 Troubleshooting with LED Indicators
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33.1 Troubleshooting with LED Indicators
Check the LED status of each module as primary diagnostics.
LED status of the CPU module
The following table lists the check points on the LED status of the CPU module.
The error status can be checked visually using the READY LED and ERROR LED.
The LED status can also be checked on the module diagnostics window using the engineering tool. ( GX
Works3 Operating Manual)
LED indicator Error
status
Program
execution
status
Description Action
READY ERROR
On Off No error Continued Normal operation 
On Minor error A minor error or warning has been detected.
Program execution and data communications
with network stations are continued.
Identify the error cause using the engineering tool, and
take an action.
Flashing Moderate
error
Stopped A programming error, parameter setting error,
or temporal noise has been detected.
Program execution and data communications
with network stations are stopped.
Identify the error cause using the engineering tool, and
take an action.
Off On/
flashing
Major error A hardware failure has been detected. No
operation cannot be performed.
Perform troubleshooting for the error module. If the
problem still exists after troubleshooting, replace the
error module. ( Page 536 When the READY LED
of the CPU Module Turns Off)
Off Hardware
failure
A hardware failure has been detected. No
operation cannot be performed.
Check that the power is supplied to the system. If the
power is supplied properly, the possible cause is a
hardware failure. Perform troubleshooting for the error
module. If the problem still exists after troubleshooting,
replace the error module. ( Page 536 When the
READY LED of the CPU Module Turns Off)
No error Power is not supplied or power went out. 
Flashing On Minor error A minor error has been detected during
online module change.
Identify the error cause using the engineering tool, and
take an action.
Off No error • The READY LED is flashing every 400ms:
Online module change is in progress.
• The READY LED is flashing every 2s:
Initial processing is being performed.

Flashing Off No error The READY LED is flashing every 2s: Initial
processing is being performed.
