Code 25000: Axis %1 hardware fault of active encoder
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical Axis %1 hardware fault of active encoder 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 = Axis name, spindle number Definitions: The signals of the currently active position actu al value encoder (NC/PLC interface signal DB31,... DBX1.5 = 1 (Position measuring system 1) or DB 31,... DBX1.6 = 1 (Position measuring system 2)) are missing, do not have the same phase, or exhibit grounding/short-circuit. The alarm can be reprogrammed in the MD11412 $MN_ALARM_REACTION_CHAN_NOREADY (channel not ready). For PROFIdrive only: MD36310 $MA_ENC_ZERO_MONITORING >100 replaces the existing PowerOn alarm by the Reset alarm 25010. Reaction: Mode group not ready. The NC switches to follow-up mode. Channel not ready. NC Start disable in this channel. Axes of this channel must be re-referenced. Interface signals are set. Alarm display. NC Stop on alarm. Channel not ready. Remedy: Please inform the authorized personnel/service depar tment. Check measuring circuit connectors for correct contacting. Check encoder signals and replace the encoder if faults are found. Monitoring can be switched off by setting MD36310 $MA_ENC_ZERO_MONITORING[n] to 100 (n = encoder number: 1,2). Program Continuation: Switch control OFF - ON.
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 25000 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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