Code 280-043D: Line is write-protected
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical Line is write-protected 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] - You tried to edit or erase a write-protected line in the preset table. - You tried to write a value in the active line of the preset table. [Error correction] - Overwriting the active preset is not allowed. Use another preset number. - The write protection was activated by your machine manufacturer. Maybe fixed datum was defined in this line. If you want to cancel write protection, contact your machine tool builder. - You defined the write protection in the TNC.SYS file. If required, cancel the write-protection there. - You tried to change line 0. It cannot be changed. [886] 10/2023
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 280-043D 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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