Illegal Address Format - Symbol Not Found

What does F004 mean?

This fault indicates that a symbolic address used in a program or message could not be resolved by the processor because the corresponding symbol was not found. This typically means the symbol is undefined or misspelled in the symbol table.

• Symbol used in the program does not exist in the controller's tag database.
• Misspelling of a symbol name in the instruction.
• Symbol was deleted but still referenced in the program.

Click steps to track your progress.

1. 1

   Verify the exact symbolic address (tag name) referenced in the program instruction or message that triggered the F004 fault.

2. 2

   Compare the identified symbolic address with the controller's tag database (symbol table) in the PLC programming software (e.g., Studio 5000 Logix Designer or RSLogix 500) for exact spelling, case sensitivity, and existence.

3. 3

   Ensure the program routine or ladder file containing the instruction using the problematic symbolic address is present, enabled, and part of the controller's scan.

4. 4

   Verify that the correct and latest version of the PLC program, including all tag definitions, has been successfully downloaded to the controller and matches the offline project.