Long crank - continues with key off

[mattbta]

I have the same issue. Had to have the trans rebuilt last April. While out, they find the leaking main rear oil seal which we could see prior. They replaced it. Also found the camshaft position sensor wires baring copper. The insulation was gone. I asked and they said they can splice in a new pigtail so they did ... great. Now I have the issue you have. Not everytime but maybe 50% of the time. Cranks without start. Maybe a pop. The second attempt starts immediatly. Just like yours. Just like you describe.
I was suspecting that possibly the wiring was mismatched on the pigtail. I am not overly educated on how the cam postion sensor exactly works but I have the factory manuals and understand the sequncing of fuel/spark based on parameters of camshaft and crankshaft. If a wire was inadvertly miswired, would it do this? That I cannot yet get an answer. I have to pull the intake off to redo that pigtail. Maybe the CMP has failed at the very time they touched it? Unlikely but possible.
I can say this, it was perfect until the wires were touched/repaired. I did not go back there with this problem because I am leary of what could happen. The trans works fine and the rear oil seal is tight. Just this. I am putting up with it for now, but irritating.
Maybe someone has additional info that can help us?
-Oldchev

I posted the same response when you asked the same question in another thread months ago. If you're pulling the intake to inspect the pigtail, put an OEM sensor in it. Then do a cam/crank variation relearn for funsies! (My chinesium cam sensor still exhibited problems even after relearn, OEM fixed it!)

Unlikely the truck would run well at all if the wires weren't correct.

 

[KVacek]

I've been a little under the weather so haven't worked on this much. It's very likely past time for a fuel pump now when it's optional rather than after it dies completely. Gauge sender has been flaky for years too.

That said, I did take the Tech 2 out there the other day and did the crank relearn (that's how this model syncs the cam and crank sensors).

Still does the crank itself long first try, then fire right up second try about half the time. When I feel better and it gets cooler I'll see if there's any way to get to the cam sensor without other disassembly. Otherwise I'll drop the tank and do that fun job first, and see if that's it.

 

[oldchev]

2004 Yukon Denali Update: Today, I used my boroscope to look at the pigtail and connector to the CMP. The CMP bolt bolt looked pretty clean compared to the other parts around it. That said, I re examined the invoce on the trans work including the pigtail connector. The Ah Ha moment occured when I saw they stated replacing the pigtail and the CMP. So, I have the GM 19420911 coming from Rock Auto.
I'll update when installed. I am pretty sure this will fix it. (fingers crossed). Stay tuned.

 

[Fless]

2004 Yukon Denali Update: Today, I used my boroscope to look at the pigtail and connector to the CMP. The CMP bolt bolt looked pretty clean compared to the other parts around it. That said, I re examined the invoce on the trans work including the pigtail connector. The Ah Ha moment occured when I saw they stated replacing the pigtail and the CMP. So, I have the GM 19420911 coming from Rock Auto.
I'll update when installed. I am pretty sure this will fix it. (fingers crossed). Stay tuned.

I don't have the whole history of this, but... has a CASE learn been done to see if that would fix it with your current issue/sensor? I know @mattbta recommended doing one. If you do change the sensor, it's recommended to be done anyway for the new sensor.

 

[oldchev]

Yesterday 9/08/23, I replaced the CMP with GM19420911.
Instantly started. It now starts first time, everytime, with the GM sensor.
As stated by several on this forum, the other types of CMP sensors could be faulty. Using the correct GM sensor eliminated my issue. BTW, it never had a start issue until after the trans work, so replacing the "good one" with a new, incorrect one caused it to fail. I have 30+ starts on it now, so calling it good.
Oh, btw, this is a difficult access repair, at least for 60+. Once you feel what you have to do, it becomes easier. You have to make room by removing top eng cover and side covers. Then I had to sit aside of the eng, on top. I could elaborate but several already have.