Code 120120: %1 see explanation
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical %1 see explanation 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 = Alarm texts are displayed below in re spect of individual c auses of the alarm Definitions: Alarm text: Alarm list is full. Pending alarms/messages c ould not be entered into the alarm list due to lack of space. The alarm cannot be deleted, as this event has made the alarm list permanently inconsistent. Alarm text: Number of alarm texts too high. The number of alarm texts is currently limited to 5000. This limit has been exceeded by the alarm text configuration. Alarm text: File %1 not found. Alarm text: Input/output error in file %1. Alarm text: Input/output error. Alarm text: Error on reading from the index file. Alarm text: Error on writing into the index file. Alarm text: Syntax error in alarm text file %1. Alarm texts are stored in files. One of these files could not be accessed properly. HMI-Alarms Diagnostics Manual (DAsl), 03/2009 Reaction: Alarm display. Remedy: Expand the alarm list (Enter maximum number in the file mbdde.ini in the section [Alarms]). Then perform a cold restart for the operator panel. Reduce the number of alarm texts. Then perform a cold restart for the operator panel. Make sure that the MMC memory on the hard disk is available after booting, or re-install the MMC software. When entering your own alarm texts, check whether the path and file name are entered correctly in mbdde.ini. 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 120120 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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