Code 231-E031: CC%2 FS outputs not "0" 0-31:%4 32-63:%5
Issue Description & Safety Warning
The Heidenhain TNC Series CNC has triggered a critical CC%2 FS outputs not "0" 0-31:%4 32-63:%5 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] - In the safety self-test, the WD.B.SPL FS outputs remain set during the watchdog test, although they were supposed to be reset. 0-31: Bit-encoded status of the FS outputs 0 to 31 31-63: Bit-encoded status of the FS outputs 32 to 63 64-95: Bit-encoded status of the FS outputs 64 to 95 96-127: Bit-encoded status of the FS outputs 96 to 127 - Short circuit of an FS output on +24 V - Hardware defective [Error correction] - Check the wiring of the FS outputs. - Exchange the hardware - Generate the service files and notify the Service Department
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 231-E031 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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