Allen-Bradley GuardLogix Safety Fault — Safety Task Fault

GuardLogix safety controller has faulted. The safety task stopped executing, and all safety outputs went to their de-energized (safe) state. All guarded motion and safety-related outputs are disabled.

Probable Causes (ranked)

• Safety partner module (1756-L7SP) communication loss with primary processor — partner not seated or failed
• Safety I/O device connection lost — Guard I/O module (1734-IB8S, 1734-OB8S) went offline
• Safety task watchdog expired — safety program execution time exceeded the configured watchdog
• CIP Safety connection timeout — safety device missed too many consecutive communication packets
• Safety signature mismatch after program change — safety lock/signature validation failed
• Safety I/O module detected internal diagnostic failure — module self-test failed

Fix Steps

1. 1 In RSLogix 5000, check Controller Properties > Safety tab for the specific safety fault code
2. 2 Check safety partner module (1756-L7SP) status LEDs — must show solid green when healthy
3. 3 Verify all CIP Safety connections — expand Safety I/O tree in Controller Organizer, look for faulted modules
4. 4 If safety I/O device offline, check its Ethernet cable and power — reseat cable, power cycle device
5. 5 If safety signature mismatch, the safety program may need revalidation — contact safety engineer
6. 6 Reset safety fault — this typically requires a deliberate reset sequence, not just clearing faults
7. 7 After reset, verify all safety I/O devices are online before attempting to run guarded operations

Suggested Replacement Parts

Parts matched to fault category: Safety Relay

Prices are estimates. Verify part numbers match your equipment before ordering.

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