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ErrorLib — Industrial Fault Code Library

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5-1-2-1

Min Supply Voltage μC2 Not Met

Beckhoff · EL1904 Digital Input Terminal

What does 5-1-2-1 mean?

The supply voltage to microcontroller 2 (μC2) within the EL1904 terminal has fallen below its minimum permissible limit. This undervoltage condition can cause unstable operation or prevent the microcontroller from functioning correctly, potentially leading to system errors or shutdowns.

Common Causes

  • External power supply voltage drops below the minimum required threshold for μC2.
  • Brownout condition or unstable power source.
  • Failing power supply unit or inadequate capacity.
  • High current draw from other components affecting μC2 voltage.
  • Low mains voltage affecting operational stability (P2-2).

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Measure the supply voltage at the terminal's power input using a multimeter.

  2. 2

    Verify the measured voltage is above the minimum specified operating voltage for the terminal (refer to technical data for specific values).

Browse all codes in this manual (6)
Verified technical data. Last updated: April 2026

Related Faults

2-1-2-1Max Supply Voltage μC1 Exceeded3-1-2-1Max Supply Voltage μC2 Exceeded4-1-2-1Min Supply Voltage μC1 Not Met
Source: Beckhoff EL1904 Digital Input Terminal
Open Manual (Page 40)Search more codes in this manual