Code 201664: <location>SI CU: No automatic firmware update
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>SI CU: No automatic firmware update 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: OFF2 Acknowledge: IMMEDIATELY (POWER ON) Cause: When booting, parameter p7826 "automatic firmware update" did not have the value "1" that is required for the automatic firmware upgrade/downgrade. This means that when the safety functions are enabled, an inadmissible combi nation of versions can occur. Note: This fault does not result in a safety stop response. See also: p7826 (Firmware update automatic) Remedy: For enabled drive-based SI monitoring: 1. Set parameter p7826 to the value 1 2. Save the parameter (p0977 = 1) and carry out a power-on reset When de-activating the drive-bas ed SI monitoring (p9601 = 0), the alarm can be acknowledged after exiting the safety commissioning mode.
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 201664 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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