A217 $0D TP5 v250.adx is used for scanning/dataloging the engine ALDL info and some general transmission functions. This the adx you will use most.
I guess I missed something here.

I got the A217 refers to the A217.ds GM data stream files. I assume the .ds files came from GM.

Where does the $0D come from?

Why the change to v250.adx? I thought the convention was to name the files A218.ADX.