Diag3:lit, Diag4:flashing

Internal Terminal Error (μC1)

Beckhoff · EL6900 Operating Instructions

What does Diag3:lit, Diag4:flashing mean?

This LED combination (Diag 3 lit, Diag 4 flashing) indicates an internal error related to microcontroller 1 (μC1) of the terminal. This is a global fault, leading to the shutdown of the terminal. Such errors typically necessitate inspection by the manufacturer.

Additional Steps

Steps 1–2 are listed in Priority Fix.

  1. 3

    Access the TwinCAT System Manager to check for any additional diagnostic messages or system events logged by the EL6900 prior to the shutdown.

Source: Beckhoff EL6900 Operating Instructions
Open Manual (Page 54)