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
Measure the supply voltage at the terminal's power input using a multimeter.
- 2
Verify the measured voltage is above the minimum specified operating voltage for the terminal (refer to technical data for specific values).
Verified technical data. Last updated: March 2026
Related Faults
Source: Beckhoff EL1904 Digital Input Terminal