Code 26002: Axis %1 encoder %2 parameterization error: number of encoder marks
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical Axis %1 encoder %2 parameterization error: number of encoder marks 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 %2 = Encoder number Definitions: 1. Rotary measuring system (MD31000 $MA_ENC_IS_LINEAR[]==FALSE) The number of encoder marks set in MD31020 $MA_E NC_RESOL[] does not correspond to the value in the drive machine data (SIMODRIVE 611D: MD1005 $MD_ENC_RESOL_MOTOR; PROFIdrive: p979) or zero has been entered in one of the two machine data. 2. Absolute measuring system with EnDat interface (MD5790 $MD_ENC_TYPE[]==4) On absolute encoders, the resolution of the incremen tal and absolute tracks s upplied by the drive is also checked for consistency. For PROFIdrive drives: Compare drive parameter p979 (and possibly other internal drive, manufacture-specific parameters stated in the relevant drive documentation) Reaction: Mode group not ready. The NC switches to follow-up mode. Channel not ready. NC Start disable in this channel. Interface signals are set. Alarm display. NC Stop on alarm. Channel not ready. Remedy: Please inform the authorized personnel/service department. Adjust machine data. For absolute encoders, possibly pending drive alarms indicating encoder problems should be evaluated. They could be the cause of incorrect entries of MD1022 $MD_ENC_ABS_RESOL_MOTOR/MD1032 $MD_ENC_ ABS_RESOL_DIRECT, which the drive reads out of the encoder itself. 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 26002 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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