037

Press RESET to clear the alarm. Access the program via EDIT mode and identify all M98 subprogram calls in the currently executing program and trace the call chain depth.

Check parameter 3107#0 (maximum subprogram nesting) on 30i/31i/32i series to verify the configured nesting limit. On 0i/16i/18i series, the limit is typically hardcoded to 4 levels and cannot be changed.

Review the subprogram structure and reduce nesting levels by consolidating subprograms or restructuring the program logic to use fewer nested M98 calls. Map out O-numbers being called: Main > O1001 > O1002 > O1003 > O1004 etc.

Verify all M99 subprogram return commands are properly paired with M98 calls and are not missing, which can cause incorrect nesting level tracking by the control.

Missing M99 commands will cause the control to lose track of nesting depth and may trigger alarm 037 prematurely.

Access OFFSET/SETTING > PROGRAM menu and list all subprograms (O-numbers) currently in memory. Examine each subprogram containing M98 calls for circular references.

Trace the M98 P_____ addresses in each subprogram to identify if any subprogram directly or indirectly calls itself. Check for patterns like O1000 contains M98 P1000 or O1000 > O2000 > O3000 > O1000.

Recursive calls may not be immediately obvious if multiple subprograms are involved in the circular call chain.

Break the circular reference by removing or redirecting the M98 call that creates the loop. Restructure the program logic to use linear or controlled repetition with M98 L___ repeat count instead of recursive calls.

Test the modified program in SINGLE BLOCK mode with DRY RUN active to verify proper program flow and confirm nesting depth stays within limits.

Check if Custom Macro option is enabled by verifying parameter 6001#0=1. Access SYSTEM > PARAM and search for parameter 6001 to confirm macro capability is active on this control.

Review the program for mixed use of G65 macro calls and M98 subprogram calls. Count the total combined nesting depth: each G65/G66 and M98 call adds one level to the stack.

G66 modal macro calls remain active and consume nesting depth until cancelled with G67.

Restructure the program to reduce combined nesting by converting macro calls to subprograms or vice versa, keeping total nesting below 4 levels on older controls or the parameter 3107#0 setting on 30i/31i/32i series.