Hey guys.

I come seeking guidance. Long story short, my 2004 350z has been giving me some grief.

It all started when my CPS (crank pos sensor) died on me last year. I replaced the visually broken sensor with an aftermarket sensor and happily continued on. A month or 2 after then I experienced the same symptoms and assumed a dud CPS. Replaced it again, but that didn’t solve my problem.

I then suspected cam pos sensor. I took the car to a workshop to put in a new clutch and smf and asked them to fix the issues while they were there. They said that they ran some diagnostics and that my timing chain is stretched (I wouldn’t be surprised if that is the case as the car has 210k km on the clock). That job is too big for them and told me to seek help elsewhere (they gave recommendations). I can do that job myself, but don’t want to unless I have to.

AI then went and sought out a second opinion from a guy that specialises in Z’s but is on the other side of the country. He reckons its just non-OEM sensors causing all this nonsense. I replaced the CPS with an OEM sensor - car still sad. I’ve now ordered OEM cam sensors - they’re arriving next week.

In the meantime, I dug up my old 2-channel oscilloscope and ran some tests.

My symptoms are as follows: All sensors installed - car won’t start. Unplug CPS - car starts and will allow me to drive around a bit, but it will ultimately die on me.

When I ran the scopes, I got some interesting results. Some of the signals seem to be inverted, which is super weird - hopefully the new OEM sensors will fix that. (For info - the aftermarket sensors were Bremi’s). I also noticed that the timing was a bit out (I think).

My scopes were taking during crank as the car didn’t want to starts. Are there any experts here that can tell me if the chain is stretched or if I’ve jumped some teeth? I have also attached a scope that I found online of a healthy vq35de at idle.

Thanks,
Rob




Both cam sensors


Healthy VQ35DE

 

What codes did you get? Was it just the cps code?

 

P0335 - CPS and P0340 - camshaft sensor bank 1.

 

Maybe someone else can chime in to confirm, but I believe you would be seeing timing related codes if it were an issue with the chains. Potentially noises too from the chain slapping around.

Have you checked the ground, power and signal to the cps connector? Maybe an issue is present in the wires.

The crank sensor and cam sensor work in tandem. The crank sensor provides information to the cam sensors, to adjust timing accordingly via vvt. I think an issue with the crank sensor can cause hiccups on the cam side, potentially throwing a incorrect code for the cam sensor. Again, wait for someone else to confirm these suspicions as I am not entirely sure.

 

Maybe someone else can chime in to confirm, but I believe you would be seeing timing related codes if it were an issue with the chains. Potentially noises too from the chain slapping around.

Have you checked the ground, power and signal to the cps connector? Maybe an issue is present in the wires.

The crank sensor and cam sensor work in tandem. The crank sensor provides information to the cam sensors, to adjust timing accordingly via vvt. I think an issue with the crank sensor can cause hiccups on the cam side, potentially throwing a incorrect code for the cam sensor. Again, wait for someone else to confirm these suspicions as I am not entirely sure.