> Exactly -- is the ECU a mysterious black box? 0r is there a description
> of how it makes its decisions anywhere?

Mike:

It is a black box, but what it does is know.  Maybe not how....
See the Van-Cafe page:
http://www.van-cafe.com/sp/8691V/8691Vtool.html

When you become the expert, then you can get a job such as
http://tinyurl.com/yvztrn

Richard