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ErrorLib — Industrial Fault Code Library

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U

Energy Supply Stop (ECM)

Fanuc · Macro B CNC Programming

What does U mean?

The potential difference across the Energy Charge Module's (ECM) Capacitor Modules is detected to be more than 300V, indicating an unsafe high voltage condition. This suggests a failure in the charging or discharge control, or a dangerous energy imbalance within the module.

Common Causes

  • Interruption in the main energy supply to the ECM.
  • Loss of DC bus voltage (e.g., below P24-2 threshold).
  • Power supply unit failure.
  • Circuit breaker tripped or blown fuse in the main power line.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Immediately stop the machine using the emergency stop button and open the external Main Circuit Contactor (MCC) of the Power supply.

  2. 2

    Measure the voltage across the Capacitor Modules (A06B-6158-H020) to confirm it exceeds 300V.

  3. 3

    Inspect the ECM Control Module (A06B-6158-H010) for proper regulation of charging and discharging operations.

  4. 4

    Check the Resistor Module (A06B-6158-H030) and its connections to ensure it can properly dissipate energy when commanded or during an emergency stop.

  5. 5

    Verify the main power supply and connected regenerative units for stable operation and correct voltage levels to prevent overcharging of the capacitor modules.

Browse all codes in this manual (26)
Verified technical data. Last updated: April 2026

Related Faults

08Regeneration Excess Alarm1Over-current at Power Running (ECM)2Over-current at Regeneration (ECM)
Source: Fanuc Macro B CNC Programming
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