Code 201611: <location>SI CU: Defect in a monitoring channel
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>SI CU: Defect in a monitoring channel 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: SERVO, VECTOR Reaction: NONE (OFF1, OFF2, OFF3) Acknowledge: IMMEDIATELY (POWER ON) Cause: The drive-based "Safety Integrated" function in the C ontrol Unit (CU) has detected a fault in the data cross-check between the CU and Motor Module (MM) and initiated a STOP F. As a result of this fault, after the parameteriz ed transition has expired (p9658), fault F01600 (SI CU: STOP A initiated) is output. Fault value (r0949, interpret decimal): 0: Stop request from the Motor Module. 1 to 999: Number of the cross-checked data that resulted in this fault. This number is also displayed in r9795. 1: SI monitoring clock cycle (r9780, r9880). 2: SI enable safety functions (p9601, p9801). Cros swise data comparison is only carried out for the supported bits. 3: SI SGE changeover tolerance time (p9650, p9850). 4: SI transition period STOP F to STOP A (p9658, p9858). 5: SI enable Safe Brake Control (p9602, p9802). 6: SI Motion enable, safety-relevant functions (p9501, internal value). 7: SI pulse suppression delay time for Safe Stop 1 (p9652, p9852). 8: SI PROFIsafe address (p9610, p9810). 1000: Watchdog timer has expired. Within a per iod corresponding to approximately 5 * p9650, too many switching operations have occurred at terminal EP of the Motor Module, or STO (including subsequent responses) has been triggered t oo frequently via PROFIsafe/TM54F. 1001, 1002: Initialization erro r, change timer / check timer. 2000: Status of the STO selection on the Control Unit and Motor Module are different. 2001: Feedback signal for safe pulse suppression on the Control Unit and Motor Module are different. 2002: Status of the delay timer SS1 on the Control Unit and Motor Module are different. 2004: Status of the STO selection for modules connected in parallel are different. 2005: Feedback signal of the safe pulse suppre ssion on the Control Unit and Motor Modules connected in parallel are different. Remedy: Re fault value = 1 to 5 and 7 to 999: - check the cross-checked data that resulted in a STOP F. - carry out a POWER ON (power off/on) for all components. - upgrade the Motor Module software. - upgrade the Control Unit software. Re fault value = 6: - carry out a POWER ON (power off/on) for all components. - upgrade the Motor Module software. - upgrade the Control Unit software. Re fault value = 1000: - check the EP terminal at the Motor Module (contact problems). - PROFIsafe: rectify contact problems/faults on the PROFIBUS master/PROFINET controller. - check the wiring of the fail-safe inputs on TM54F (contact problems). Re fault value = 1001, 1002: - carry out a POWER ON (power off/on) for all components. - upgrade the Motor Module software. - upgrade the Control Unit software. Re fault value = 2000, 2001, 2002, 2004, 2005: - check the tolerance time SGE changeover and if required, increase the value (p9650/p9850, p9652/p9852). - check the wiring of the safety-relevant inputs (SGE) (contact problems). - check the causes of STO selection in r9772. Ac tive SMM functions (p9501= 1) can also cause STO to be selected. - replace the Motor Module involved. SINAMICS-Alarms Diagnostics Manual (DAsl), 03/2009 Note: CU: Control Unit EP: Enable Pulses (pulse enable) MM: Motor Module SGE: Safety-relevant input SI: Safety Integrated SS1: Safe Stop 1 (corresponds to Stop Category 1 acc. to EN60204) STO: Safe Torque Off / SH: Safe standstill SMM: see r9772
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 201611 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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