Code 230651: <location>SI MM: Synchronization with Control Unit unsuccessful
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>SI MM: Synchronization with Control Unit unsuccessful 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
Message value: %1 Drive object: All objects Reaction: OFF2 Acknowledge: IMMEDIATELY (POWER ON) SINAMICS-Alarms Diagnostics Manual (DAsl), 03/2009 Cause: The drive-based "Safety Integrated" function is reques ting synchronization of the safety time slices on the Control Unit and Motor Module. This synchronization rout ine was unsuccessful. Note: This fault results in a STOP A that cannot be acknowledged. Fault value (r0949, interpret decimal): Only for internal Siemens troubleshooting. Remedy: - carry out a POWER ON (power off/on) for all components. - upgrade the Motor Module software. - upgrade the Control Unit software. Note: MM: Motor Module SI: Safety Integrated
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 230651 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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