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ErrorLib — Industrial Fault Code Library

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I/O-LED 4-0

Data fault on internal bus or Internal bus interruption on Coupler (Fault code 4, argument 0)

Wago · Modular I/O System PROFIBUS DP

What does I/O-LED 4-0 mean?

A data fault or a complete interruption of the internal bus has occurred, originating from or directly at the Fieldbus Coupler itself. This critical issue prevents any communication with all connected I/O modules, rendering the entire node inoperable.

Common Causes

  • Hardware defect in the coupler's internal bus interface circuitry
  • Severe data corruption or physical interruption of the internal bus within the coupler

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Replace the Coupler.

Browse all codes in this manual (21)
Verified technical data. Last updated: April 2026

Related Faults

BUS-LED 1-1Insufficient configuration data (Fault code 1, argument 1)BUS-LED 1-2Excessive configuration data (Fault code 1, argument 2)BUS-LED 2-nFaulty configuration byte n (Fault code 2, argument n)
Source: Wago Modular I/O System PROFIBUS DP
Open Manual (Page 101)Search more codes in this manual