Could The Ecm Be Bad?

I have had various posts regarding an intermittent starting problem with my 2000 venture. When I turn the key on the lights come on and when I finishish turning the key all the way it wont start, if I hold the key it will usually turn over but there is a delay of sometimes 1 sec to 15 or longer. I was just curious what the ECM controls and if it is tied in with the pk3 at all. The symptoms of the no start are the same as a pk3 lockout (no spark no fuel). Just curious about the ECM and what it does. Thanks.