User`s manual

Troubleshooting basics Troubleshooting
MELSEC System Q, Hardware 11 – 1
11 Troubleshooting
This chapter describes errors that may occur during system operation, how to locate the errors,
and measures against the errors.
11.1 Troubleshooting basics
In order to increase the reliability of the system, resuming the system operation promptly after
correcting a problem is one of the important factors as well as using reliable device. To promptly
start up the system, the trouble cause must be located and eliminated correctly.
The basic three points to be followed in the troubleshooting are as follows:
Visual inspection
● Behavior of the programmable controller and other connected devices (in STOP mode or in
operation)
● Applicability of the power supply
● States of input and output devices
● Installation states of the power supply module, CPU module, I/O module, intelligent function
module, and extension cables
● Wiring (Cables including input and output cables)
● Display status of all indicators such as "POWER", "RUN", "ERR.", and "I/O" LEDs
● Setting status of all switches such as the number of extension base units and data retention
time during power failure
After checking above points, connect a programming device and monitor the operating status
and programs of the programmable controller.
Error checking
Check how the error status changes by operating the following to the programmable controller.
● Set the mode switch to STOP.
● Clear the Latch area with the L.CLR switch or with the programming device.
● Power on and off.*
* Resetting and powering off clears the error codes stored in the completion status area for the dedicated
instruction and the buffer memory states of intelligent function modules. Before resetting or powering off,
backup the error codes and buffer memory states that are relevant to the error.
Narrowing down the scope for identifying trouble cause
Estimate the troubled part in accordance with above items (visual inspection, error checking).
Trouble causes could occur in:
● Programmable controller or external devices
● I/O module or others
● Sequence program
The troubleshooting flowcharts on following pages provide more help for identifying trouble
causes.