The other day my engine light came on so I ran a diagnosis and came up with trouble code 12. My Chilton's indicates that this is due to having no NE signal being input to the ECM for 2 seconds or more after STA turns ON. It identifies the NE circuit, distributor, STA circuit, and/or ECM being the trouble area. Does anyone know how to test these areas; in particular, the NE circuit and STA circuit. Advice on where to start with this problem would be great, too!

EDIT: It may be helpful to mention that when I turn the key, it doesn't turn over. I have to start my truck by jumping the starter, which works every time. I've had to do this occasionally for about a year, but it has progressed to an every time sort of thing, unless I try starting it immediately after turning it off. Perhaps my best bet would be replacing the ECM.