Code 402-000C: FK programming: Incomplete input
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical FK programming: Incomplete input 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 FK sequence is not complete at its program end. You will have to program additional data or NC blocks. [Error correction] * Add FK blocks as the end or edit them. * Add the missing data or NC blocks within the program. Note: - In each block, program the data that do not change. (Nonprogrammed data are treated as unknown.) - If the first block of an FK contour is an FCT or FLT block, you must program at least two NC blocks with the gray path function keys to fully define the direction of contour approach. An FK contour must not be programmed immediately after an LBL command
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 402-000C 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.
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