I/O Module Readback Error

What does E3-525 mean?

A readback error has occurred on an I/O bus module. This means the value read back from an output or an internal register does not match the value that was commanded or expected. This indicates a potential hardware fault, wiring issue, or corrupted internal state, compromising output verification.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Verify the configured output value against the actual physical output using a multimeter if applicable.

2. 4

   If the error persists, replace the I/O module as it likely has an internal hardware fault.