The Haynes car manuals (Amazon sell them) have wiring diagrams - as an ex computer engineer I find them well laid out but a little difficult to follow easily mainly because of lack of experience. When a signal cable arrives at a component like the ecu all you may see is a box with a number in it. You look the number up in a table and it will just say ecu.
You do not mention the specific fault you have so experts may have difficulty helping you (I am not an expert).
You may do better using a specialist auto electrician.
Good luck...
Peccavi
January 2010