On what I've read before, and on what I read here, there isn't any "cheatware" "inserted in the code".
The whole code cheats. Or, as this article quotes "in the US, .... the [engine] heating function can probably be considered a defeat device"
There isn't a magic "cheat device" hidden in the code. It just doesn't do what it required to do: maintain emmissions control while in normal running.