Code 27204: PROFIsafe: double assignment MD %1[%2] - MD %3[%4]
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical PROFIsafe: double assignment MD %1[%2] - MD %3[%4] 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 = MD name 1 %2 = MD array index for MD name 1 %3 = MD name 2 %4 = MD array index for MD name 2 Definitions: A double assignment has illegally been parameterized in the specified machine data: $A_INSE parameterized on DMP as well as PROFIsafe modules. Involved MDs: - MD $MN_SAFE_IN_HW_ASSIGN - MD $MN_PROFISAFE_IN_ASSIGN $A_INSE parameterized on several PROFIsafe modules. Involved MD: - MD $MN_PROFISAFE_IN_ASSIGN Reaction: Mode group not ready. Channel not ready. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm. Remedy: Correct the MD. Program Continuation: Switch control OFF - ON.
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 27204 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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