This thread identifies "power posts" and auto-rest fuses in an older RV, but the principle is the same for all of us.
I'm not so much concerned about the power post as being a problem when trying to trace voltage to the ECM, but I can definitely see how a bad or failing auto-reset fuse would be.
So the "OP" might want to examine this if for nothing else for general knowledge. Here's the link:
Normally, I would say that you should also be looking for a poor ground while you are giving your electrical system a full-physical. However, in this case, I believe you said you were getting 0V to your ECM.
Questions For The Experts:
* Is there a auto-rest fuse in line to the ECM? And if so, will that create the "open voltage" in this case? Or could this fuse lower voltage
or pass a dirty signal to the ECM if it's a part beginning to fail? And if so, where is this fuse located?
* Or maybe there a relay involved with passing power to the ECM? ...And does the key switch activate this relay so the relay can available battery power to the ECM? (That is to say, this relay switches whatever voltage the battery has.) If so, where is this relay located. ...Or can we trace it by looking for wire that goes to the battery.
* That said, if there is a wire that goes direct to the top of the engine battery (maybe a 10 or 12 gauge or so) which the ECM relies upon, maybe this 0V problem is due to a bad connection at the battery? I just don't know? And I don't know what some of those separate wires do... that are located on top of my battery. So I"m asking if one of these wire is for the ECM power? My guess is "No". My guess is that there is a relay next to the main power post located behind my engine batter bank... or maybe it's one of those fuse blocks mounted on the battery side wall.
What I am getting at is this: I don't know how the ECM receives power or how that power is switched by the key-ignition? Can someone describe this for all of us and verify there is or is not a auto-fuse or relay involved in this circuit? Thank you!