401ES5433

OKI ES5433 Error 401: Communication Fault

The OKI ES5433 error 401 is a technical warning indicating a break in communication between the device and the local area network (LAN). This happens frequently when the printer loses its IP assignment, the network cable is poorly connected, or the print server is unresponsive. When investigating why does OKI ES5433 show error 401, we generally find infrastructure issues or poorly implemented static network configurations.

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Common causes

  • 1Disconnected, damaged, or poor-contact network (RJ45) cable.
  • 2IP address conflict within the local network.
  • 3Negotiation failure between the network card and the network switch.
  • 4External interference due to poorly shielded cables.

Solutions

Diagnóstico rápido

The error shows when you try to print from the network but the device appears 'offline'. Check if the LAN port lights on the back are on (typically a solid green and a blinking yellow/orange).

Solución paso a paso

  1. Disconnect the network cable and reconnect it; you should hear a 'click'.
  2. Reboot your router to renew the DHCP server lease.
  3. If using a static IP, ensure there is no IP address conflict with another device on the network.
  4. If the error continues, try using a different, high-quality network cable (CAT6).

Prevención y mantenimiento

Perform preventative network cable maintenance annually. Keep cables from being stretched, sharply bent, or placed near sources of electromagnetic interference (motors, transformers).

Cuándo llamar a un técnico

If the printer remains disconnected after testing with a new cable and different switch ports, the internal network card might be faulty.

Ficha técnica del equipo

  • Technology: Color Laser A4
  • Network: Ethernet 10Base-T/100Base-TX/1000Base-T
  • Consumables: OKI ES5433 Series Toner
  • Support: https://www.oki.com/support/es5433

Steps to follow

  1. 1

    Check cables

    Disconnect and reconnect the network cable (RJ45) to ensure no loose contacts.

  2. 2

    Network reboot

    Power off the router and printer, then turn them back on to refresh the IP address.

  3. 3

    IP Configuration

    Verify on the control panel that the printer has a valid IP address within the subnet.

Frequently asked questions

This error signals that the printer cannot communicate with the print server or local network, causing job interruption.

Yes, a worn-out or dirty RJ45 cable often causes persistent communication errors.

This error is not related to consumables, but rather to network configuration and cable infrastructure.

Use high-quality Category 6 (CAT6) cables and ensure the network controller firmware is up to date.