The Siemens drive fault code F7902 (or 7902) Motor Stalled (or "Motor out of step"). This fault occurs when the drive detects that the motor is not rotating despite a torque or current being applied, or it has lost synchronism with the drive's output frequency. Common Causes Mechanical Overload:
| Cause Category | Specific Cause | |----------------|----------------| | Fieldbus hardware | Loose or damaged PROFIBUS/PROFINET cable; missing terminating resistor (PROFIBUS) | | Configuration mismatch | Incorrect telegram type in drive vs. PLC; wrong device address; baud rate mismatch | | PLC/master side | PLC not in RUN; master not sending cyclic data; I/O controller stopped | | Parameter settings | P2040 (monitoring time) too short; P0922 not matching telegram; P8840 (fieldbus interface enable) incorrect | | Bus scan/initialization | Bus not fully started before drive enables communication | siemens drive fault code 7902
Check the Drive’s Environment: Ensure the drive is operating in an environment that meets Siemens’ specified conditions. Check for adequate ventilation and that the ambient temperature is within recommended limits. The Siemens drive fault code F7902 (or 7902)
If the above points pass but the fault persists, suspect drive hardware: Device address matches drive station address (P0918 for
Insufficient Current/Torque Limits: The drive is unable to provide enough torque to move the load because limits (p0640) are set too low.
Need further assistance? Consult the official Siemens manual for your specific drive model (function diagrams 8010–8020 for output monitoring). For hands-on help, Siemens Technical Support can provide remote diagnostic assistance using Starter or STARTER software to trace current waveforms in real time.
Use a digital multimeter and, if available, a megohmmeter.