Wiring issue, unusual situation

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Schojo

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Hi I’m new here but I’m having a kind of odd issue, I’m almost positive it’s just a wiring issue somewhere just not sure where. I have a 2004 GMC Yukon 2WD 5.8L
A few months ago the head went out so we bought and replaced the heads on the engine. When we replaced the head we didn’t take off or remove all the wiring like we probably should’ve we kinda just moved the bundle to the side. We got codes for replacing the o2 sensor and crankshaft sensor so we did. Everything was running fine after that, for a few weeks actually and then randomly car shuts off while active driving and then continues this pattern of working and then randomly dying while driving. No codes get thrown when car dies either which is why I think it’s something electrical. We checked the fuel line, it’s primed, we have correct pressuring everything is the way it’s suppose to be. We cleaned the sensor connectors that we could. We can’t locate all of the grounds I try to look up the placements and I only found one on the back of the engine and I know there’s 2 more I’m just not sure where. That ground is definitely part of the problem as it’s just gunked up in black. When we try to start the car it will just crank but not start and if it does start it’s like 50/50 on if it stays alive for a few days or just dies again right away. If this isn’t enough info please let me know I can always add more if you have a question
 

Joseph Garcia

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Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in this area will chime in.
 

justchecking

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Randomly shutting off with no codes is often a failing crankshaft position sensor.
 

Fless

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When you replaced the crank sensor, was a CASE relearn done with a scanner? It's recommended and quick, if successful; not always necessary but it can prevent some potential issues.

Try that relearn, and consider reinstalling the old crank sensor (and do the relearn). Hopefully you have an OE one to use.
 

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