Code 201701: <location>SI Motion CU: STOP B initiated
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>SI Motion CU: STOP B initiated 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: Drive object: SERVO, VECTOR Reaction: OFF3 Acknowledge: IMMEDIATELY (POWER ON) Cause: The drive is stopped via STOP B (braking along the OFF3 deceleration ramp). As a result of this fault, after the time param eterized in p9556 has expired, or the speed threshold parameterized in p9560 has been undershot, mess age C01700 "STOP A initiated" is output. Possible causes: - stop request from the higher-level control. - subsequent response to the message C01714 "SI Motion: Safely reduced speed exceeded". - subsequent response to the message C01711 "S I Motion: Defect in a monitoring channel". Remedy: - remove the fault cause in the control and carry out a POWER ON. - carry out a diagnostics routine for message C01714. - carry out a diagnostics routine for message C01711. This message can only be acknowl edged as follows in the acceptance test mode without POWER ON: - motion monitoring functions integrated in the driv e: Via Terminal Module 54F (TM54F) or PROFIsafe - motion monitoring functions with SINU MERIK: Via the machine control panel. Note: 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 201701 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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