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ErrorLib — Industrial Fault Code Library

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Uv2

Control Power Supply Voltage Fault

Yaskawa · J1000

What does Uv2 mean?

The voltage supplied to the control drive input power is too low. This can occur if parameter L2-02 is changed from its default value without installing a Momentary Power Loss Ride-Thru unit, or if there is damage to the control power supply wiring or internal control circuitry, impacting drive control stability.

Common Causes

  • External 24VDC control power supply failing or providing unstable voltage.
  • Internal control power supply failure within the drive's control board.
  • Incorrect control voltage parameter (L2-02) for the installed hardware configuration (e.g., without a Momentary Power Loss Ride-Thru unit).
  • Loose or corroded connections in the control power wiring.
  • Overload condition on the drive's internal 24VDC output for external devices.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    1. Measure the voltage at the dedicated control power input terminals (e.g., 24VDC, R1/S1/T1 for control board) using a multimeter.

  2. 2

    2. Verify the external control power supply (if used) is providing stable voltage and sufficient current capacity.

  3. 3

    3. Check parameter L2-02 to ensure it is set correctly for the drive's configuration (e.g., default value or specific for ride-thru unit).

  4. 4

    4. Inspect the control board for any signs of internal voltage regulator failure or physical damage.

  5. 5

    5. Ensure all control wiring connections are secure and free of corrosion.

  6. 6

    6. If parameter L2-02 was intentionally modified, revert it to default or install the appropriate Momentary Power Loss Ride-Thru unit as required.

Browse all codes in this manual (59)
Verified technical data. Last updated: April 2026

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Source: Yaskawa J1000
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