Allen-Bradley Fault 01 — Watchdog Timeout
What This Fault Means
A watchdog timeout fault indicates the controller's scan time exceeded the configured watchdog timer. The controller halts execution to prevent unpredictable outputs.
Common Causes
- Program scan time exceeds watchdog timer setting
- Excessive math or loop operations in a single scan
- Communication module consuming too many resources
- Firmware bug or corrupted project file
Recommended Fix
- Check the watchdog timer setting in Controller Properties — increase if the scan time legitimately needs more time.
- Profile the task scan times in RSLogix 5000 / Studio 5000 under Task Properties → Scan Time.
- Break heavy computations into multiple scans using state machines.
- If the fault persists after tuning, reflash the controller firmware and reload the project.
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