What does the ecm actually control on a 1997 Cadillac Deville

It's OBDll so quite alot.

I want specifics not oblique answers. What does it control if it is OBD 2 or obd 1

What is the issue then if you want me to get into detail......You better get a big pad of paper and a new pen!!!

Fuel injectors, throttle position sensor information, camshaft position sensor information, crankshaft position sensor information, spark plug timing, air fuel mixture, emissions, transmission control module, ABS control module, AC control module, I forgetting something but this should answer your question. The shop repair manuals should cover most of these repairs unless it is something Joe Shade tree mechanic shouldn't be messing with!!!