8 ERROR CODES AND ERROR MESSAGES
8.5 Troubleshooting in bus connection
8.5.1 Locating error positions
8 - 8
If a cause cannot be located by the troubleshooting procedures specified in section 8.2
when the GOT is bus-connected to the PLC CPU, troubleshoot the cause as follows.
(1) How to locate error positions:
(a) Use of peripheral devices
Using the peripheral devices such as GX Developer, check what type of the
error occurs on the PLC CPU and, based on the error message on the PLC
CPU and the check points (See item (2) below), check each module and
cable for installation and earthing statuses.
(b) Error timing
Check the timing of errors.
1) An error occurs when the power is turned on or immediately after the
PLC is reset:
The error may be detected by the initial processing of the PLC CPU.
In this case, because the faulty module may not be identified, use only
an END instruction for the sequence program and remove the modules
one by one until the error does not occur.
When the error is eliminated after a specific module has been removed,
the module may be causing the error.
2) An error occurs after a specific operation or several seconds:
The error may occur in the sequence program. Check the error step
where the error may occur and the sequence program in that step.
The sequence program can be diagnosed throughout by merely using an
END instruction for the sequence program.
3) An error occurs when a specific device operates:
The mis-operation may be caused by noise.
Check that any signal line such as bus cable is not laid out too close to
the operating device. If the line is too close to the device, separate the
line 100 mm or more from the device.
(c) Locating the module where an error occurs:
Based on the PLC CPU error codes and special resister information (See
item (2)), locate a specific module where an error occurs.
By the method stated above, correct the sequence program or replace the faulty
module with a new one, and check whether the error occurs.
If the error continues to occur, it may have another cause.
Referring to section 8.5.2, locate the error position further.
8 - 8