Code 120404: Setting up acyclic link %1 failed.%nSwitch off/on control, drives and HMI.
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical Setting up acyclic link %1 failed.%nSwitch off/on control, drives and HMI. 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 = Name of connection Definitions: Setting up an acyclic link with a drive unit for file transfer fr om/to this drive unit has failed. The file could not be transfe rred from/to this drive unit. The affected drive unit has the bus number and slave address specified in the link name: /DRIVE_<Bus number>_<Slave address>. Reaction: Alarm display. Remedy: Execute the following meas ures in the sequence specified until t he process leading to the alarm can be repeated successfully: 1. Switch off/on control, drives and HMI, and then repeat the process leading to the alarm. 2. Load PROFIBUS configuration (HW Config) with same PLC and CP-Subnet-ID in PLC and CP, switch off/on control and HMI, and then repeat the process leading to the alarm. 3. Return to factory settings of the affected driv e unit, switch off/on control, drives and HMI, and then repeat the process leading to the alarm. 4. Contact Siemens AG, Industry Sector, I DT MC, Hotline (Phone/Fax: see Alarm 1000) regarding the error text. Program Continuation: Internal
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 120404 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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