6681 EFB Communication Loss Fault in ABB ACS880 Drive

6681 EFB Communication Loss in the ABB ACS880 Drive indicates that the drive has detected a loss of communication with the Embedded Fieldbus (EFB) master. The ACS880 continuously exchanges control commands, reference values, status information, and diagnostics with the fieldbus master through the built-in embedded fieldbus interface. If communication is interrupted beyond the configured timeout period, the drive generates Fault 6681.

The response of the drive to this communication loss is determined by Parameter 58.14 – Communication Loss Action, which defines how the drive reacts when EFB communication is lost.

This fault generally indicates a problem with the fieldbus network, communication cable, master controller, or embedded fieldbus interface rather than an internal drive hardware failure.

Possible Causes

  • Embedded Fieldbus (EFB) communication interrupted.
  • Fieldbus master is offline.
  • Fieldbus master is in an error state.
  • PLC or network controller has stopped communicating.
  • Loose or damaged communication cable.
  • Poor connection at the XD2D connector on the control unit.
  • Damaged fieldbus connector or communication port.
  • Incorrect fieldbus configuration.
  • Incorrect network address or node configuration.
  • Communication timeout due to network congestion.
  • Electrical noise or EMI affecting fieldbus communication.
  • Broken or improperly terminated communication cable.
  • Fieldbus master software or controller failure.
  • Embedded fieldbus interface malfunction.
  • Incorrect communication parameters after commissioning.
  • Firmware incompatibility between the drive and fieldbus master.

Solutions

  • Cycle power to the drive if appropriate and check whether the fault clears.
  • Verify the status of the fieldbus master (online, offline, or error).
  • Ensure the PLC or network controller is operating correctly.
  • Inspect the communication cable connected to the XD2D connector.
  • Verify all communication connectors are securely connected.
  • Check the communication cable for damage or loose connections.
  • Verify the network address and communication settings.
  • Inspect fieldbus cable shielding and grounding.
  • Check network termination resistors where applicable.
  • Review Parameter 58.14 – Communication Loss Action to confirm the configured drive response.
  • Verify communication parameters match the fieldbus master configuration.
  • Restart the fieldbus master if necessary.
  • Update firmware if recommended by ABB.
  • Replace damaged communication cables or connectors.
  • Replace the control unit if the embedded fieldbus interface is defective.
  • Contact ABB technical support if the fault persists.

Additional Information

The ABB ACS880 includes an Embedded Fieldbus (EFB) interface that allows direct communication with industrial automation systems such as PLCs and distributed control systems. Through this interface, the drive receives start and stop commands, speed or torque references, and transmits operating status, alarms, and diagnostic information.

When the control unit no longer receives valid communication from the fieldbus master within the configured timeout period, it generates Fault 6681.

The drive's behavior after communication loss depends on Parameter 58.14 – Communication Loss Action, which may be configured to:

  • Generate a fault and stop the drive.
  • Generate a warning.
  • Coast to stop.
  • Ramp to stop.
  • Continue operating using a predefined fallback behavior (depending on the application configuration).

Unlike an internal communication fault, Fault 6681 is specifically related to the external embedded fieldbus network between the drive and the fieldbus master.

Common Symptoms

  • Drive trips with Fault 6681.
  • Drive stops responding to PLC commands.
  • Start or stop commands are ignored.
  • Speed or torque reference is lost.
  • Drive enters the communication loss action configured in Parameter 58.14.
  • Fieldbus communication status changes to offline.
  • PLC reports communication timeout.
  • Fault appears intermittently due to poor cable connections.
  • Communication is restored after reconnecting the network.
  • Drive resumes normal operation once communication is re-established (depending on configuration).

Recommended Troubleshooting Sequence

  1. Check the status of the fieldbus master.
  2. Verify the PLC or controller is online.
  3. Inspect the communication cable connected to the XD2D connector.
  4. Verify all communication connectors are securely connected.
  5. Check the communication cable for damage.
  6. Verify network addressing and communication parameters.
  7. Inspect cable shielding and grounding.
  8. Verify network termination if applicable.
  9. Review Parameter 58.14 – Communication Loss Action.
  10. Restart the fieldbus master if necessary.
  11. Update firmware if recommended by ABB.
  12. Replace damaged communication cables or connectors.
  13. Replace the control unit if the embedded fieldbus interface is defective.
  14. Contact ABB technical support if the fault persists.

EFB Communication Check Table

Check PointAction
Fieldbus masterVerify online status and normal operation
PLC / ControllerConfirm communication is active
Parameter 58.14Verify Communication Loss Action setting
XD2D connectorInspect cable connection
Communication cableCheck for loose or damaged wiring
Communication connectorsEnsure secure connections
Network addressVerify correct node configuration
Communication parametersConfirm they match the fieldbus master
Cable shieldingInspect grounding and shielding
Network terminationVerify correct termination where required
FirmwareUpdate if recommended by ABB
Embedded fieldbus interfaceInspect for hardware failure
ABB technical supportContact if the fault remains after inspection

Preventive Maintenance Tips

  • Inspect fieldbus cables and connectors during scheduled maintenance.
  • Keep the XD2D connector clean and securely connected.
  • Verify cable shielding and grounding to minimize electrical interference.
  • Periodically inspect communication cables for wear or damage.
  • Confirm network termination resistors are correctly installed.
  • Back up fieldbus configuration parameters before making changes.
  • Verify PLC and drive communication settings after commissioning or firmware updates.
  • Use only ABB-approved communication accessories where applicable.
  • Keep firmware updated according to ABB recommendations.
  • Record recurring communication faults to assist long-term network diagnostics.

Proper inspection of the embedded fieldbus network, verification of the XD2D connector, confirmation of the fieldbus master status, correct configuration of Parameter 58.14 – Communication Loss Action, and routine maintenance of communication cables and connectors will help prevent recurring 6681 EFB Communication Loss faults in ABB ACS880 drives, ensuring reliable network communication, stable process control, and dependable long-term drive operation.

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