Code 27254: PROFIsafe: F module %1, error on channel %2; %3<ALSI>
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical PROFIsafe: F module %1, error on channel %2; %3<ALSI> 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 = Channel type, channel number %3 = System variable array index extension Definitions: The F module signals that an error occurred in the interface of the specified channel. This alarm is only triggered for ET200S F modules. The type of channel (input or output channel) is indicated by the abbreviations IN and OUT in %2. A specific alarm message can be programmed for each of the system variables on the HMI via parameter %3: - %3 = 1....64: Error in system variables $A_INSE[1...64] - %3 = 65...128: Error in system variables $A_OUTSE[1...64] - %3 = -1: Error in an input or output channel for which ther e is no SPL assignment 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. Remedy: Check wiring. Wiring OK: replace F module. 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 27254 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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