2006 Nissan Altima 2.5L P0340 No Start?

This Nissan came in on a tow truck earlier in September. The complaint was a Crank, No Start. Of course, when I went out and turned the key, it started right up. No codes. Did all the usual checks. Found nothing. I kept the car, at the customer's request, and drove it like it was my own, taking it home, running my errands....for about a week and a half. No problems. I gave the car back an told her to bring it back when it was broke. No charge.

Last night, it was dropped of by tow-truck. The complaint was Crank, No Start. Of course, when I went out and turned the key, it started right up. This time, however, I had a hard P0340. (Cam Shaft Position Circuit) I scoped the CAM sensor and had no signal. Power and Ground, good. After verifying circuit integrity I put a new CAM sensor in it and restored the CAM signal.

I charged her for a CAM sensor and sent her down the road. I told her to keep her fingers crossed because....THE CAM SENSOR IS NOT REQUIRED FOR THIS CAR TO START AND RUN.

Both times it was towed in, it had been a hot engine that would not RE-start. Not a cold start. I am theorizing that, when the engine is HOT, the valve timing DOES need the CAM signal?

I am confident that the CAM sensor was bad and needed replaced. I am NOT confident that it was the cause of the No Start condition.

Any thoughts?

How many miles on this one? I ask because my first thought is a timing issue, especially when hot. I understand that the CMP isn't needed to start, but I do know that the ECM can get confused by timing or chain stretch problems, resulting in no spark/injection pulse. In the past, on the 1.8L engines, the trick was to disconnect the CMP and see if it'll start. I'm not positive that still applies to the 2.5L.

You could scope both the CKP and CMP and see what the timing looks like before digging further. I don't have a cranking capture to share, just an idling capture off an '06.



My other thought is with 'sync' issues between old (the CKP) and new (CMP) sensors. I've never witnessed this, but I've heard from other techs that intermixing sensors on the 2.5L and 3.5L engines can cause issues due to differences in sensor performance. Not enough to gamble on a new CKP, I know, especially because the CKP is the tough one to replace. :silly:

Thank you for the input and the KNOWN GOOD, Tyler!

This car IS up there in the miles. Closing in on 220,000, if I recall correctly. I will get it back in and check CMP/CKP correlation.
I hadn't thought about a stretched chain. For as many miles that it has, it runs nice and smooth. No clatter. No misfiring. Seemingly, the worst part about it is the faded paint job on the hood.

No problem! I really hope I'm wrong about the chain speculation, 'cause most customers I know wouldn't put chains on a vehicle with that many miles. But hey, if the rest of it is shiny, why not?

Side note, I always appreciated how Nissan built the firing order into the CMP waveform. :silly: One of those cam/crank setups that makes logical sense when viewed on a scope.

Tyler wrote: especially because the CKP is the tough one to replace.

You weren't kidding! :woohoo: I called this one back in to scope the cam/crank. It was such a pain just to FIND the CKP...with a bore scope. :blink: It didn't take long to bail on the idea of scoping the CKP. It was going to take more time than it was worth, considering the Milage...It was closing in on 224,000. New car shopping is in the near future, for this customer.

pole71 wrote: You weren't kidding! :woohoo: I called this one back in to scope the cam/crank. It was such a pain just to FIND the CKP...with a bore scope. :blink: It didn't take long to bail on the idea of scoping the CKP.

Yeah, sorry sir, it's not a good time. The whole thing is made worse by the stupid lock-tab system Nissan uses. Plus, the timing cover is separate from the valve cover, so you can't just pull the valve cover and have a look at the chain tensioner.