I had this engine, as PaperTRW pointed out it does not feature TMCC as originally issued. Can be upgraded to TMCC and Railsounds (comes with SignalSounds) by installing the separately sold upgrade kits.
Lionel.com has the instructions for the conventional/command ready Alco C420s
C-420 Diesel - Command Ready - 5/00 (Rev. 3.1)