7391

Encoder 2

ABB · ACS880

What does 7391 mean?

A feedback fault has occurred with Encoder 2. This is identical in nature to the Encoder 1 fault but pertains to the second encoder feedback channel, leading to similar loss of accurate motor position/speed data. This can affect dual-feedback systems or applications requiring redundant speed/position control.

Common Causes

  • Broken or damaged wiring in the Encoder 2 cable (e.g., open circuit on A/B/Z signals, short to ground, intermittent connection).
  • Encoder 2 power supply failure (e.g., loss of 5VDC or 15VDC at the encoder).
  • Loose or corroded connections at the drive's second encoder input terminals (e.g., X22, X23) or at the encoder itself.
  • Incorrect encoder type or pulse count parameter settings (e.g., P22-01, P22-02) for the installed Encoder 2.
  • Excessive electromagnetic interference (EMI) affecting signal integrity of Encoder 2, especially on unshielded cables.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Verify 5VDC or 15VDC power supply to Encoder 2 at its connector (e.g., pins 1 and 2) using a multimeter.

  2. 2

    Check continuity of all signal wires (A, /A, B, /B, Z, /Z) from Encoder 2 to the drive's second input terminals (e.g., X22, X23).

  3. 3

    Inspect all terminals at Encoder 2 and its corresponding drive input for looseness, corrosion, or signs of damage.

  4. 4

    Confirm Encoder 2 parameters (e.g., P22-01 Encoder 2 type, P22-02 Pulses per revolution) are correctly configured.

  5. 5

    Ensure Encoder 2 cable shielding is properly terminated and grounded at both the drive and motor end to mitigate EMI.

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Verified technical data. Last updated: March 2026

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