840

Incorrect SERCOS phase selection (->%d).

Bosch Rexroth · Motion Control

What does 840 mean?

During SERCOS startup, an incorrect communication phase was selected. Only phases 0 to 4 are permissible, and they must be configured in ascending order, incrementing by one step. This is a servo loop or drive fault.

Common Causes

  • Incorrect SERCOS communication phase selected during startup.
  • SERCOS phases not set in ascending order or not in steps of one.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check the commanded SERCOS communication phase setting and adjust it if necessary.

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Verified technical data. Last updated: March 2026

Related Faults

1290SERCOS state class 1: Motor overtemperature cut-off %s-axis.1300SERCOS state class 1: Interface error %s-axis.1297SERCOS state class 1: Under-voltage fault %s-axis.
Source: Bosch Rexroth Motion Control
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