Code 201659: <location>SI CU: Write request for parameter rejected
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>SI CU: Write request for parameter rejected 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: A_INF, B_INF, S_INF, SERVO, TM41, TM54F_MA, TM54F_SL, VECTOR Reaction: OFF2 Acknowledge: IMMEDIATELY (POWER ON) SINAMICS-Alarms Cause: The write request for one or several Safety Integrated parameters on the Control Unit (CU) was rejected. Note: This fault does not result in a safety stop response. Fault value (r0949, interpret decimal): 1: The Safety Integrated password is not set. 2: A reset of the drive parameters was selected. However, the Safety Integrated parameters cannot be reset, as Safety Integrated is presently enabled. 3: The interconnected STO input is in the simulation mode. 10: An attempt was made to enable the STO function although this cannot be supported. 11: An attempt was made to enable the SBC function although this cannot be supported. 12: An attempt was made to enable the SBC function although this cannot be supported for a parallel circuit configuration. 13: An attempt was made to enable the SS1 function although this cannot be supported. 14: An attempt was made to enable the PROFIsafe communication - although this cannot be supported or the version of the PROFIsafe driver used on the CU and MM is different. 15: An attempt was made to enable the motion moni toring functions integrated in the drive although these cannot be supported. 16: An attempt was made to enable the STO function although this cannot be supported when the internal voltage protection (p1231) is enabled. See also: p0970, p3900, r9771, r9871 Remedy: Re fault value = 1: - set the Safety Integrated password (p9761). Re fault value = 2: - inhibit Safety Integrated and again reset the drive parameters. Re fault value = 3: - end the simulation mode for the digital input (p0795). Re fault value = 10, 11, 12, 13, 14, 15: - check whether there are faults in the safety function alignment between the Control Unit and the Motor Module involved (F01655, F30655) and if requir ed, carry out diagnostics for the faults involved. - use a Motor Module that supports the required f unction ("Safe Torque Off", "Safe Brake Control", "PROFIsafe/PROFIsafe V2", "motion monito ring functions integrated in the drive"). - upgrade the Motor Module software. - upgrade the Control Unit software. Re fault value = 16: - inhibit the internal voltage protection (p1231). Note: CU: Control Unit MM: Motor Module SBC: Safe Brake Control SI: Safety Integrated SS1: Safe Stop 1 (corresponds to Stop Category 1 acc. to EN60204) STO: Safe Torque Off / SH: Safe standstill See also: p9501, p9601, p9620, p9761, p9801
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 201659 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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