Code 207900: <location>Drive: Motor locked/speed controller at its limit
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>Drive: Motor locked/speed controller at its limit 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 Reaction: OFF2 (NONE, OFF1, OFF3, STOP1, STOP2) Acknowledge: IMMEDIATELY Cause: Motor has been operating at the torque limit longer than the time specified in p2177 and below the speed threshold set in p2175. This signal can also be initiated if the speed actual value is oscillating and the speed controller output repeatedly goes to its limit. See also: p2175, p2177 SINAMICS-Alarms Remedy: - check that the motor can freely rotate. - check the torque limit: For a positive direction of rotation r1538, for a negative direction of rotation r1539. - check the parameter, message "Motor locked" and if required, correct (p2175, p2177). - check the inversion of the actual value (p0410). - check the motor encoder connection. - check the encoder pulse number (p0408). - for SERVO with encoderless operation and motors with low power ratings (< 300 W), increase the pulse frequency (p1800). - after de-selecting basic positioning, check t he torque limits when motoring (p1528) and when regenerating (p1529).
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 207900 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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