Allen-Bradley PanelView HMI Communication Fault

PanelView or PanelView Plus HMI lost communication with the ControlLogix/CompactLogix PLC. Screen displays communication error or tag values show as '####' or 'Comm Err'.

Probable Causes (ranked)

• Ethernet cable between HMI and PLC (or network switch) disconnected or damaged
• PLC went to fault mode or was taken offline — HMI cannot read tags
• HMI application shortcut tag path incorrect after PLC controller name change
• Network switch port failure between HMI and PLC
• HMI IP address changed or conflicts with another device
• PLC EtherNet/IP module overloaded — too many HMI connections competing for resources

Fix Steps

1. 1 Check Ethernet cable at HMI and switch — verify link LED on both ends
2. 2 Verify PLC is in RUN mode — check keyswitch or RSLogix 5000
3. 3 Ping PLC IP address from HMI terminal settings or from a laptop on the same network
4. 4 In FactoryTalk View ME/SE, check RSLinx Enterprise shortcut paths — controller name must match PLC
5. 5 Restart the HMI application — press Ctrl+Alt+Del on PanelView Plus to access Windows desktop if needed
6. 6 If multiple HMIs on the network, check for IP conflicts — each must have a unique IP
7. 7 Power cycle the HMI as last resort — hold power button or cycle the 24VDC supply

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