Code 27251: PROFIsafe: F module %1, %2 reports error %3
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical PROFIsafe: F module %1, %2 reports error %3 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
Parameters: %1 = PROFIsafe address %2 = Reporting component (master/slave) %3 = Error code Definitions: An error occurred in the PROFIsafe communication between the F master and the specified F module which was detected by the component (master/slave) shown in parameter %2. The error code specifies the error type: - %3 = TO: The parameterized communication timeout was exceeded - %3 = CRC: A CRC error was detected - %3 = CN: An error in the time sequence of the F messages was detected - %3 = SF: F master error, NCK/PLC are no longer synchronous - %3 = EA: Communication error, slave sends empty messages Reaction: Mode group not ready. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm. Trigger a STOP D/E (settable via MD $MN_SPL_STO P_MODE) on all axes with safety functionality. Diagnostics Manual (DAsl), 03/2009 Remedy: Check the DP wiring. Restart F slave modules. Restart the NCK/PLC. Program Continuation: Clear alarm with the RESET key. Restart part program
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 27251 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
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