John,
From page 39 of The DCS O Gauge Companion 2nd Edition:
Under DCS 4.10 or higher, to recover a PS2 engine that has a DCS ID# that's outside of the normal range, proceed as follows
• Set the engine on a piece of track controlled by TIU #1. The Recover Engine feature only works with TIU #1. You must not have any other engines powered up on any track connected to TIU #1 while attempting to recover an engine
• Apply power to TIU #1
• Power on the DCS Remote
• Press the Menu button and use the thumbwheel to scroll to SYSTEM. Press the thumbwheel to select it
• Use the thumbwheel to scroll to RECOVER ENGINE. Press the thumbwheel to select it
• The remote will display "Attempting Recovery of Lost Engine, Please wait!!!"
• If the remote is able to recover the engine it will display "Engine Recovered" and return to the Engine Setup menu. The newly recovered engine will be automatically Factory Reset by the remote. Refer to section DCS Menus, Advanced Menu later in this book for an explanation of the Factory Reset command
• Turn TIU #1 off and then back on
• The engine may now be added to the DCS remote using the ADD ENGINE command as
described in section DCS Menus, System Menu earlier in this book
This and a whole lot more is all in "The DCS O Gauge Companion 2nd Edition", now available for purchase as an eBook or a printed book from MTH's web store site! Click on the link below to go to MTH's web page for the book!