Code 25001: Axis %1 hardware fault of passive encoder
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical Axis %1 hardware fault of passive 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 from the currently inacti ve position actual value encoder ar e missing, or they are not of the same phase, or they exhibit grounding/short-circuit. For PROFIdrive only: MD36310 $MA_ENC_ZERO_MONITORING >100 replaces the existing PowerOn alarm by the Reset alarm 25011. MD36310 $MA_ENC_ZERO_MONITORING >100 replaces the existing Reset alarm by the Cancel alarm 25011. Reaction: Alarm display. Remedy: Please inform the authorized personnel/service depar tment. Check measuring circuit connectors for correct contacting. Check encoder si gnals and replace the encoder if faults are found. Switch off monitoring with the corresponding inte rface signal DB31,... DBX1.5 / 1. 6 = 0 (Position measuring system 1/2 ). Monitoring can be switched off by setting MD36310 $MA_ENC_ZERO_MONITORING[n] to 100 (n = encoder number: 1,2). Program Continuation: Clear alarm with the RESET key. Restart part program
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 25001 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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