Old Hand Fault Finder

Allen-Bradley PowerFlex 525 F081: DSI Comm Loss

What it means Communication between the drive and its Modbus or DSI master device was interrupted.

✓ Checked against the manual (Oct 2026): meaning and actions match the official fault table. Manual page.

Likely causes

  • Loose or damaged comm cable
  • Master device stopped or faulty
  • Electrical noise

Checks, in order

  1. Check comm cabling and the Modbus or DSI settings and status
  2. Review C125 Comm Loss Action
  3. Grounding terminals C1 and C2 may improve noise immunity

Source

Source (reworded, not copied): Rockwell Automation, PowerFlex 520-Series AC Drives User Manual, publication 520-UM001O-EN-E (September 2025), Chapter 4 Troubleshooting, PDF page 162. Official manual (PDF). Fault numbers and names can differ between firmware versions.