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FB ESTOP Bit 2

E-Stop Discrepancy Error - Input Group 3

Beckhoff · TwinSAFE Logic FB

What does FB ESTOP Bit 2 mean?

A discrepancy has been detected between the two channels of input group 3 for the FB ESTOP. This indicates that the redundant E-Stop input signals are not in agreement, suggesting a potential failure of one channel, a wiring issue, or an incorrect switching sequence. This will prevent the E-Stop function from operating safely and halt the machine.

Common Causes

  • One channel of the E-Stop device's redundant contacts for Input Group 3 is intermittently failing to close or open.
  • Loose terminal screw connection on one of the safety controller input terminals for Input Group 3 (e.g., terminal X3.1).
  • Degradation of the E-Stop button's internal spring mechanism, affecting reliable contact switching.
  • Voltage drop or noise on the power supply to the E-Stop input circuit, affecting one channel more than the other.
  • Safety function block configuration error, setting incorrect input logic for Input Group 3 channels.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Test the E-Stop button for Input Group 3 by pressing and releasing, observing the real-time status of both channels (e.g., LEDs IN_G3_CH1, IN_G3_CH2) on the safety controller.

  2. 2

    Measure the voltage potential between each E-Stop input terminal (e.g., X3.1 and X3.2) and the common ground during actuation.

  3. 3

    Check the continuity of the wiring for both channels from the E-Stop device back to the safety controller's Input Group 3 terminals.

  4. 4

    Confirm the safety controller's parameter settings for Input Group 3 (e.g., P_ESTOP_G3_LOGIC) are correctly configured for the E-Stop device type.

  5. 5

    Perform a thorough visual inspection of all components in the E-Stop circuit for Input Group 3, including cables, connectors, and terminal blocks.

Browse all codes in this manual (60)
Verified technical data. Last updated: April 2026

Related Faults

0x401FPress Not Moving After Start Command0x4020Press Unexpectedly Stopped After Starting0x4021Insufficient Press Movement
Source: Beckhoff TwinSAFE Logic FB
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