Anti Theft Re-engaged, Blowing ECM fuse and ignition fuse on BCM

[Gtstorey]

Sorry to here that BCM isn't the actual problem.

Don't put in a larger fuse. That is asking for a melted wiring harness or worse.

I'm confident in the work we did tying this to the C4 connector or wiring leading to the C4 connector. You are going to have to start tracking down the outputs of the BCM which isn't going to be easy. You can probably eliminate any of the higher load circuits fed from the 40amp BCM 2 fuse. Look for feeds going to the other modules and the 5v reference type circuits. At some point you are going to pretty much have to find all of the wiring diagrams and connector pinouts for you donor and work to eliminate them one at a time.

You might want to rig up or buy an incandescent test light and probe all of the pins on the BCM connectors. You will look for the ones that light up full brightness and then work out which ones of those are likely to properly go to ground. You could try this with the OHM meter and see what the resistance is but I would prefer the light bulb test.

I also could see this coming down to deliberately and methodically cutting the wires one at a time until you find the problem.

 

[KingChuck24]

Did some more testing this morning and this is what I found:
I am getting continuity between c4 d1 and c4 d8 even when the battery in unplugged. I thought this should not be the case as it would need to be in the run position.
I couldn't find a way to test the theft resistor or at least could not get a good reading. It is possible it is blown out though because I was able to get continuity when the key was in between c2 56 and 62 but when I turned it to the start position I got no resistance.

Thanks for the suggestion ross, I will try that tonight.

 

[KingChuck24]

Just saw your response Gtstorey. The thing is I am not very good at understanding all of wiring but I think I will give it a go. I do have a friend that owns a shop that is pretty good with electrical stuff and if I really cannot figure it out I might end up dropping it with him.

 

[Gtstorey]

You are at the point now, that there are a LOT of people who couldn't figure this out. I think I could in person, but It might take a few days. And would require the full wiring diagrams.

 

[KingChuck24]

I think I am going to call up my friend and see what he thinks, he might know someone else too that could help in person. Kind of a crazy idea that probably wouldn't work but the Chevy dealer probably knows the ins and outs of the cobalt so if they somehow accepted to service it they could maybe figure it out. Probably would not go this route though.

 

[Sluggonaut]

I am getting continuity between c4 d1 and c4 d8 even when the battery in unplugged. I thought this should not be the case as it would need to be in the run position.

What do you mean when you use the term 'continuity'? Testing continuity means checking the circuit to see if it is open or closed and in my limited electrical testing knowledge, is typically done without voltage.

I'm just asking because your statement about continuity is confusing to me and I'm wondering if you are testing for voltage instead of continuity based on your statement.

 

[Gtstorey]

Hopefully he's not testing for voltage with the battery unplugged.

 

[KingChuck24]

Haha no I am testing voltage with the battery connected.

 

[Gtstorey]

Did some more testing this morning and this is what I found:
I am getting continuity between c4 d1 and c4 d8 even when the battery in unplugged. I thought this should not be the case as it would need to be in the run position.
I couldn't find a way to test the theft resistor or at least could not get a good reading. It is possible it is blown out though because I was able to get continuity when the key was in between c2 56 and 62 but when I turned it to the start position I got no resistance.

Thanks for the suggestion ross, I will try that tonight.

I missed seeing this earlier. For these test questions to mean anything, you are going to have to be clear on the status of everything related. Was the C2 connector disconnected when this was checked? Where you checking on the module side or harness side? And then you have to confirm what is going on in the "power distribution schematics".

Do you have the schematics that show C4 D1 and D8. No way of knowing without it.

 

[Sluggonaut]

Haha no I am testing voltage with the battery connected.

Ok, so what would the battery being unplugged have to do with your continuity results? You said you were getting continuity even with the battery unplugged and that seemed to surprise you.

Changing the position of a switch in a circuit should affect continuity but having the battery plugged in or unplugged should not affect continuity.

 

[Goblinfanclub1234]

this might be unrelated but I also shorted my battery when it was connected and I ended up getting a new starter, I think I fried the internal wiring. might be worth consideration.

 

[KingChuck24]

This issue ended up being resolved a while back I just never posted the reason.

The ecu ended up being completely fried and had to be replaced. My mechanic ended up figuring this out after getting his head close to the ecu to try to find wiring and he smelt something burnt. It ended up being the ecu.