Code 207903: <location>Drive: Motor speed deviation
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>Drive: Motor speed deviation 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: NONE Acknowledge: NONE Cause: The absolute value of the speed difference from the two setpoints (p2151, p2154) and the speed actual value (r2169) exceeds the tolerance thre shold (p2163) longer than tolerated (p2164, p2166). The alarm is only enabled for p2149.0 = 1. Possible causes could be: - the load torque is greater than the torque setpoint. - when accelerating, the torque/current/power limit is reached. If the limits are not sufficient, then it is possible that the drive has been dimensioned too small. - the speed controller is inhibited (refer to p0856; refer to Kp/Tn adaptation of the speed controller). - for closed-loop torque control, the speed se tpoint does not track the speed actual value. - for active Vdc controller. - the encoder pulse number was incorrectly parameterized (p0408). The signal is not generated if the ramp-function gener ator tracking prevents the setpoint and actual speed from drifting (moving) apart. Only for vector drives: For V/f control, the overload condition is de tected as the Imax controller is active. See also: p2149 (Monitoring configuration) Remedy: - increase p2163 and/or p2166. - increase the torque/current/power limits. - enable the speed controller. - for closed-loop torque control: The speed setpoint should track the speed actual value. - correct the encoder pulse number in p0408 or mount the correct tachometer. 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 207903 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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