What made them go away? After 15 years I would imagine that even in a safety critical component such as this (ie if it ain't bust don't fix it) there would be redesign, revision and update.
The code was rewritten...for the fadec software. Everyone flying the ch47 knows that....
Nope!
The Rev 1 version software only removed the spurious Eng Fail caption by reducing the sensitivity of the routine - that's it!