Troubleshooting steps
Check PLC diagnostic files verify configuration review system status
Allen-Bradley PLC
21 – Communication timeout
Communication timeout with remote device
Details
Communication timeout with remote device. Check PLC diagnostics and configuration.
Error typefault
MeaningCommunication timeout
Typical causesPLC fault communication fault configuration error
SolutionsCheck PLC diagnostic files verify configuration review system status
Severityhigh
Catalog references
Vendor Information
Allen-BradleyFault Code 21
Utilities
Troubleshooting Steps
Related
Related Allen-Bradley PLC Codes
FAQ
Common questions
Can I clear the fault?
Usually requires power cycle. Check diagnostic files first