EL
ErrorLib
Brands
||
  1. Home
  2. SMA
  3. Sunny Boy Solar Inverter
  4. 401/404
About·Privacy·Terms

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.

401/404

Grid fault (Frequency Fluctuation)

SMA · Sunny Boy Solar Inverter

What does 401/404 mean?

The inverter has disconnected from the utility grid because a stand-alone grid was detected or a very large, short-term change in the power frequency occurred. This disconnection is a protective measure.

Common Causes

  • Detection of a stand-alone grid (islanding condition).
  • Significant short-term fluctuations in the power frequency.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Check the grid connection for significant short-term frequency fluctuations.

Browse all codes in this manual (23)
Verified technical data. Last updated: April 2026

Related Faults

101Grid fault10252[Interface]: communication disrupted10253[Interface]: connection speed goes to [100 Mbit / 10 Mbit]
Source: SMA Sunny Boy Solar Inverter
Open Manual (Page 49)Search more codes in this manual