Allen-Bradley Fault 04 — Recoverable I/O Fault
What This Fault Means
A recoverable I/O fault signals that an I/O module reported an error that does not require a full controller reset. The controller continues to run but the affected module data may be stale.
Common Causes
- Momentary communication loss to an I/O module
- Module firmware version mismatch with controller
- Intermittent cable or connector issue
- Module configuration changed while online
Recommended Fix
- Check the module fault code in the I/O tree for the specific error.
- Verify firmware compatibility between the module and controller (use Rockwell Compatibility Matrix).
- Inspect cables and connectors for intermittent physical issues.
- Clear the fault via the CLR Major Fault routine or a GSV/SSV instruction in your logic.
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