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ErrorLib — Industrial Fault Code Library

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938

Low read-back volts from DC bus circuit.

Otis · DSD 412 Elevator System

What does 938 mean?

This fault indicates that a low voltage read-back is detected from the DC bus circuit. This can occur during Self-Tune (Function #997) or Self-Diagnostic (Function #998). For drives larger than 300 amps DC, this involves discrete wires.

Common Causes

  • Missing wire connected to the bus voltage feedback circuit.
  • Component problem where the feedback voltage divider ratio does not match the one identified in the Cube ID PCB.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check for any missing wires connected to the bus voltage feedback circuit.

Browse all codes in this manual (57)
Verified technical data. Last updated: April 2026

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117/118SERIAL COMMUNICATION FAULT400MOTOR OVERLOAD FAULT401EXCESSIVE FIELD CURRENT
Source: Otis DSD 412 Elevator System
Open Manual (Page 92)Search more codes in this manual