Visible PLC faults:
1. Module shows a red light (restart the module; if it still shows red after restarting, replace the PLC module. When replacing, the wiring plug does not need to be changed; just unplug the old module and plug in the new one).
2. All devices in the centralized control cannot start. First, check if the PLC CPU is functioning normally; next, check if the communication is normal (use an industrial control machine to run the command prompt, enter the DOS interface, and input the Ethernet module address, e.g., ping 192.168.1.1 to see if it responds. If it responds, it will show ttl=64 or 128; if it does not respond, it will show timeout). If there is no response, check the network cable and switch communication module.
