Allen-Bradley PLC Minor Fault — EtherNet/IP Connection Loss (Type 20)

A configured EtherNet/IP connection to a remote device has timed out. The connection faulted but the controller continues running. I/O data from the faulted connection is invalid.

Probable Causes (ranked)

• Ethernet cable disconnected or damaged between controller and remote device
• Remote device (VFD, I/O adapter, HMI) lost power or crashed
• Network switch port failure or switch power loss
• IP address conflict — two devices assigned the same IP address
• RPI (Requested Packet Interval) too short for network congestion level
• Managed switch VLAN or port security configuration blocking CIP traffic

Fix Steps

1. 1 In RSLogix 5000, expand I/O Configuration — find the module with yellow warning icon
2. 2 Check Ethernet cable at both ends — verify link LED is lit on switch port and device port
3. 3 Ping the remote device IP from a laptop on the same subnet — confirm network path is good
4. 4 Power cycle the faulted remote device — wait 30 seconds for full restart
5. 5 Check for duplicate IP addresses — use RSLinx Classic Browse or Rockwell BOOTP/DHCP tool
6. 6 Increase RPI timeout in module connection properties if timeouts are intermittent under load
7. 7 Check managed switch port status and VLAN configuration if applicable

Suggested Replacement Parts

Parts matched to fault category: Network Module

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

Need a deeper diagnosis with photo analysis and AI-powered troubleshooting?