Code 402-000A: FK programming: Illegal operation
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical FK programming: Illegal operation alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
[Cause of error] The following are illegal in open FK sequences: PGM END (program end), CYCL DEF 7-11 and 26 (coordinate transformations), TOOL CALL (tool change), and PGM CALL (program calls) [Error correction] First resolve the FK sequence or program the objectionable operation at another location in the program. 10/2023 [1191]
Source: HEIDENHAIN NC Error Messages — TNC7/640/620/320/128, CNC PILOT 640, MANUALplus 620 (10/2023)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Heidenhain TNC Series CNC Alarms
Heidenhain controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 402-000A on the TNC Series CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Heidenhain's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4497 Heidenhain TNC Series CNC codes.
Have a better solution?
Help the industrial community by sharing your repair experience for code 402-000A.
Need a searchable reference for more Heidenhain TNC Series CNC manuals?
We structure equipment manuals into searchable code, title, cause, solution, safety note, and source-reference data. Send a PDF and example searched codes when you need public pages, private search, or structured exports.
Space reserved for Google AdSense / Industrial Affiliate Links
Monetization target for 2026