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Press EDIT mode, search for the program number that was active when alarm occurred. Check alarm history at ALARM > HISTORY screen to identify exact program number.

Search the macro program for all DO statements (DO1, DO2, DO3, etc.). Count each DO instruction and verify each has a corresponding END1, END2, END3 statement matching the DO level number.

Check nested DO loops carefully. Each DO level must have proper END pairing: DO1...END1, DO2...END2, DO3...END3. Maximum nesting is typically DO1 through DO3 depending on control series.

Incorrect nesting order (e.g., DO1-DO2-END1-END2 instead of DO1-DO2-END2-END1) will also trigger this alarm.

Add the missing END statement at the appropriate location in the macro program. Reset alarm with RESET key, verify program syntax by running background edit check (Parameter 3107#3=1 enables background edit), then test macro execution.

Navigate to EDIT mode and display the affected macro program. Scroll to the end of the program and verify the program structure is complete and not truncated.

Check Parameter 3107 (Edit enable settings) and Parameter 3202#0 (Program protection). If protected programs were partially edited, corruption may occur. View SYSTEM > PARAM > search 3107 and 3202.

Setting Parameter 3202#0=1 protects all programs. Ensure protection is disabled before editing macros.

If program was recently transferred, delete the corrupted program and re-transfer from verified backup source. Use EDIT > DELETE > enter program number > execute.

After re-loading program, perform syntax check by setting Parameter 3107#3=1 (background edit) and let control scan program. Monitor DIAGNOSIS > OPERATOR MESSAGE for any additional syntax errors.

Review the macro program for IF-THEN-GOTO statements and GOTO commands within DO loops. Trace all possible execution paths to ensure END statements are always reached.

Using GOTO to jump out of a DO loop without proper END execution violates macro syntax rules.

Check for conditional statements that may skip the END. All program paths within a DO loop must pass through the corresponding END statement before loop exit.

Restructure the macro logic to ensure END statements are encountered in all execution paths. Use WHILE-DO-END structures as alternative if conditional looping is required.

Test the corrected macro with variable conditions. Monitor in MDI or MEM mode with single block (SINGLE BLOCK button ON) and feed hold to verify proper loop execution and termination.