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ErrorLib — Industrial Fault Code Library

Disclaimer: ErrorLib is an independent technical reference tool. While we aim for accuracy, always verify with the manufacturer’s official service manuals before performing maintenance on industrial equipment. ErrorLib is not affiliated with the brands listed.

43

Encoder fault

Vacon · NXS NXP

What does 43 mean?

A problem has been detected with the encoder signals, such as missing channels (A or B), reversed direction, or a missing encoder board. This prevents accurate motor speed and position feedback, leading to unstable or incorrect motor control in closed-loop applications.

Common Causes

  • Encoder feedback cable damage (e.g., broken conductor, short circuit, or shielding fault) leading to signal loss.
  • Improper encoder wiring connections to the drive's encoder option board terminals (e.g., A/A- swapped, 5V/0V shorted).
  • Mechanical damage to the encoder unit itself (e.g., bearing failure, disc misalignment, optical sensor failure).
  • Incorrect encoder configuration parameters (e.g., P4-01 (Encoder type), P4-02 (Pulses per revolution)) not matching the installed encoder.
  • Missing or faulty encoder option board in the drive slot.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Visually inspect the encoder cable for any physical damage from the encoder to the drive.

  2. 2

    Power down the drive and use a multimeter to check for continuity on each conductor of the encoder cable.

  3. 3

    Verify all encoder feedback wires are correctly terminated at the drive's encoder option board (e.g., A, A-, B, B-, Z, Z-, 5V, 0V).

  4. 4

    Check parameter P4-01 (Encoder type) and P4-02 (Pulses per revolution) to ensure they match the installed encoder's specifications.

  5. 5

    Monitor encoder signals using the drive's diagnostic menu (e.g., P4-03 (Encoder speed feedback)) during slow motor rotation.

  6. 6

    If available, swap the encoder option board with a known good one to rule out board failure.

Browse all codes in this manual (54)
Verified technical data. Last updated: April 2026

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Source: Vacon NXS NXP
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