Cause : ACX: Writing to the parameter back-up file was unsuccessful. Writing to at least one parameter back-up file PSxxxyyy. in the non-volatile memory was unsuccessful.

Remedy:

- check the file attribute of the files (PSxxxyyy., CAxxxyyy., CCxxxyyy.) and, if required, change from "read only" to "writeable".

- check the free memory space in the non-volatile memory. Approx. 80 kbyte of free memory space is required for every drive object in the system.

- replace the memory card or Control Unit.