Code 4402: %1 causes a machine data reset
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical %1 causes a machine data reset 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 = Machine data Definitions: If this machine data is set, the current machine dat a values are overwritten by the default values at the next ramp-up. Under certain circumstances, th is may cause data loss (even in the buffered memory). Reaction: Alarm display. Remedy: Please inform the authorized personnel/service departm ent. If the control includes user data that has not yet been saved, then a data backup must be performed before the next NCK power-up. By manually resetting the altered MD to the value it had before the last power-up, reorganization of the memory can be avoided. Program Continuation: Alarm display showing cause of alarm disapp ears. No further operator action necessary.
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 4402 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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