I/O Module Troubleshooting
First, check the status of the PWR LED indicators on the I/O modules. If the PWR LED on
the PLC unit is on, but there are I/O modules which have PWR LEDs that are off, check the
connections between the modules. If the I/O module PWR LEDs remain off, replace those
modules.
Troubleshooting input modules is slightly different from troubleshooting output modules.
Please refer to the proper subsection:
• Input module troubleshooting
• Output module troubleshooting
Input Module Troubleshooting
The input modules (including the PLC built-in inputs) can have the following symptoms:
Symptom Necessary Action
Input signal is on, but
the LED indicator on
the module is off.
Check the external power input voltage on the terminal block.
Check whether the terminal block is attached correctly.
If the input voltage is correct but the LED indicator is still off, replace the input module.
The LED indicator is
on, but the PLC does
not work as expected.
Check whether the PLC unit RUN LED is ON. If not, put the PLC in RUN mode.
Check the I/O configuration with the programming software. (See “How to Check the I/O
Configuration” on the next page.)
Connect the programming software and check the X bit related to the input point that is on.
(See “How to Check the I/O Status” later in this section for instructions.)
If the X bit is off, replace the input module.
CLICK PLC Hardware User Manual, 6th Edition, Rev. F – C0-USER-M
6–6
Chapter 6: Troubleshooting
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