What causes fault code AB-PF-COMM (PowerFlex VFD Fault â€” Communication Loss (F081/F100 Series))?

Ethernet cable disconnected between drive and network switch. Drive embedded EtherNet/IP adapter crashed â€” needs power cycle. PLC scanner or EN2T communication module faulted or overloaded. Network switch port failure â€” no link LED on the port connected to the drive. IP address conflict or wrong IP assigned to the drive. RPI timeout too short in the PLC I/O configuration for this drive

How do I fix fault code AB-PF-COMM?

Check Ethernet cable at drive port and switch â€” verify link LED is lit on both. Ping the drive's IP address from a laptop to verify network connectivity. Power cycle the drive to reset the embedded communication adapter. In RSLogix 5000, check the drive's I/O connection status â€” look for specific CIP error codes. Verify drive IP address matches the PLC I/O configuration â€” use drive keypad menu or Rockwell BOOTP tool. Increase RPI (Requested Packet Interval) in the PLC I/O tree for this drive connection. Check PLC EN2T or embedded Ethernet port status â€” verify it is not overloaded with too many connections

PowerFlex VFD Fault â€” Communication Loss (F081/F100 Series)

AB-PF-COMM

PowerFlex drive lost communication with the PLC over EtherNet/IP, DeviceNet, or embedded network port. Drive went to configured fault action (stop, coast, or hold last speed).

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allen-bradley powerflex vfd drive communication ethernet/ip network connection loss

Probable Causes (ranked)

Ethernet cable disconnected between drive and network switch
Drive embedded EtherNet/IP adapter crashed â€” needs power cycle
PLC scanner or EN2T communication module faulted or overloaded
Network switch port failure â€” no link LED on the port connected to the drive
IP address conflict or wrong IP assigned to the drive
RPI timeout too short in the PLC I/O configuration for this drive

Fix Steps

1 Check Ethernet cable at drive port and switch â€” verify link LED is lit on both
2 Ping the drive's IP address from a laptop to verify network connectivity
3 Power cycle the drive to reset the embedded communication adapter
4 In RSLogix 5000, check the drive's I/O connection status â€” look for specific CIP error codes
5 Verify drive IP address matches the PLC I/O configuration â€” use drive keypad menu or Rockwell BOOTP tool
6 Increase RPI (Requested Packet Interval) in the PLC I/O tree for this drive connection
7 Check PLC EN2T or embedded Ethernet port status â€” verify it is not overloaded with too many connections

Suggested Replacement Parts

Parts matched to fault category: Network Module

Allen-Bradley 1756-EN2T EtherNet/IP Module P/N: 1756-EN2T ControlLogix EtherNet/IP module, dual port, DLR capable

Amazon $850.00 Grainger $1050.00

Siemens CM 1542-1 PROFINET Module P/N: 6GK7542-1AX00-0XE0 S7-1500 PROFINET IO controller, 2-port switch

Amazon $650.00 Mouser $720.00

Managed Industrial Ethernet Switch 8-Port P/N: SE2-SW5U 8-port managed switch, DIN rail, 10/100 Mbps, IGMP snooping

AutomationDirect $145.00 Amazon $120.00 Mouser $155.00

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

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