(1) It is the software failure that causes the flashing of the PLC error indicator. For example, if the hardware configuration of the PLC program is different from the actual PLC configuration. At this time, modify the hardware configuration of the PLC program to make it the same as the actual one and redownload the plc program into the PLC , then the error indicator will not flash.
(2) It is the hardware failure that causes the error indicator of PLC to be on. The PLC detects the fatal errors which will affect the normal running. For example: Program programming error, system memory exception and so on.