Code 20081: [Channel %1: ] Axis %2 braking position cannot be accepted as a new reversing position
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical [Channel %1: ] Axis %2 braking position cannot be accepted as a new reversing position 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 = Channel number %2 = Axis number Definitions: On changing the reciprocation reversal from external sources, the braking position cannot be accepted as a new reversing position, since changing the reversal point via handwheel or JOG key is active. Reaction: Alarm display. Remedy: Deselect VDI signal "Change reversal point" and reselect it either - with "Reciprocation reversal from external sources" or - by changing the reversal point by means of handwheel or - by changing the reversal point via JOG key. Program Continuation: Alarm display showing cause of alarm disapp ears. No further operator action necessary.
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 20081 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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