CompactLogix PLC went to Fault Mode

Automation PLC
1

Rockwell PLC 1769-L19ER went into fault mode. After clearing from the studio 5000, PLC came to run mode. But the digital inputs and outputs were not set. I.e., LED not turned ON. why?

2

The 3 most likely root causes (from what you described)

  1. Field 24 VDC to IN/OUT power missing or a blown fuse → no I/O LEDs.

  2. Modules inhibited / connection not established after the fault clear.

  3. Output “On Fault/Program” action set to Reset and never re-armed with a proper RUN transition or wiring issue.