Code 207459: <location>EPOS: No zero mark
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>EPOS: No zero mark 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
Message value: Drive object: SERVO, VECTOR Reaction: OFF1 (OFF2, OFF3) Acknowledge: IMMEDIATELY Cause: After leaving the reference cam, the axis has traversed the maximum permissible distance between the reference cam and zero mark without finding the zero mark. Remedy: - check the encoder regarding the zero mark - check the maximum permissible distance between the reference cam and zero mark (p2609). - use an external encoder zero mark (equivalent zero mark) (p0495). See also: p0495 (Equivalent zero mark, input termi nal), p2609 (EPOS search for reference, max. distance ref. cam and zero mark) SINAMICS-Alarms Diagnostics Manual (DAsl), 03/2009
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 207459 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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