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ErrorLib — Industrial Fault Code Library

Disclaimer: ErrorLib is an independent technical reference tool. While we aim for accuracy, always verify with the manufacturer’s official service manuals before performing maintenance on industrial equipment. ErrorLib is not affiliated with the brands listed.

F01651

Synchronization, safety time slices unsuccessful

Siemens · SINAMICS G120

What does F01651 mean?

Synchronization of safety time slices within the Control Unit was unsuccessful, which can prevent proper and safe operation of the drive. This might indicate a transient issue or a deeper problem with the unit's internal timing or processing, affecting safety integrity.

Common Causes

  • Internal timing or synchronization error within the Control Unit's safety processor (F-CPU).
  • High internal processor load preventing the F-CPU from maintaining real-time safety slice synchronization.
  • Electromagnetic interference (EMI) affecting the internal communication or clock signals of the Control Unit.
  • Defective internal hardware component responsible for safety time slice management.
  • Corrupted firmware or safety program loaded onto the F-CPU.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Perform a power cycle of the entire drive system (Control Unit and Power Module) to attempt re-synchronization.

  2. 2

    Check for external sources of severe EMI close to the drive's Control Unit that could disrupt internal electronics.

  3. 3

    Verify the drive's firmware version is up-to-date and compatible with any connected safety modules or higher-level controllers.

  4. 4

    Reset safety-relevant parameters (e.g., using P9700=0 and then re-commissioning) to clear potential configuration inconsistencies.

  5. 5

    Monitor the drive's diagnostic buffer for other concurrent internal communication faults (e.g., F01662) that might indicate a deeper hardware issue.

Browse all codes in this manual (109)
Verified technical data. Last updated: April 2026

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Source: Siemens SINAMICS G120
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