[irmerm]

P0340 (Cam sensor) and chain stretch - My story

Previous thread for mysterious no-start condition here:
http://www.evoxforums.com/forums/showthread.php?t=57045

I decided to go ahead an do a new thread on this issue following the troubleshooting that has so far transpired.

Summary:
Car is stock under the hood except for UICP, stock tune. 73k miles on the clock. I got a CEL the other day after a fill-up and revving my engine while sitting at a light (just for kicks, maybe to 5k). I drove the car home with no issues and then went on a shopping trip about an hour later, again with no issues. The next day I tried to start the car and it just cranked but would not fire. I got replaced the battery after having the stock battery tested and this did not improve the issue. I got a code reader and it spat out code P0340 for intake camshaft position sensor circuit malfunction. Cleared the code and retried cranking and it set the code again after a few seconds of cranking.
I have since:
- Checked harness voltage at the connector to the sensor, getting a good ground and 5 volts on the two outside terminals
- Swapped the intake and exhaust cam sensors with no effect
- Swapped in both sensors from a friend's car with no effect (his car ran fine with my sensors)
- Popped off the valve cover and inspected the timing chain and cams for damage and they look fine
- Verified fuel and spark. Found fuel on spark plug, but no spark when cranking.
- Poured over the service manual entry for this code and come to the conclusion that the ECM is now the most likely culprit

I am glad to report that the ECM is still covered under the Federal Emissions Warranty. I'm about to embark on an adventure in getting a definite diagnosis as well as possible warranty replacement of the ECM.

Any input as to alternate diagnoses is appreciated and I'll update the thread as the saga goes on.
​

 

[WraithX]

First

 

[irmerm]

Update:
the one step I was missing from the service manual's diagnostic procedure was checking the sensor signal with an oscilloscope. I asked around at work today, but no one seems to know anyone who owns a scope. So, I set about making my own 'soundcard oscilloscope', which basically uses a PC's soundcard and some software to graph the sensor activity. This indicates that the signal to the ECM is indeed a good one and that the ECM must have failed. I am uploading a video of the diagnosis to youtube right now and will post an update when it's available. I'll be calling Mitsu tomorrow to have the car towed.

 

[tk421]

PM sent.

 

[spikester603]

are you sure the timing chain hasn't stretched? you wont be able to see it with your eyes Im afraid.

How many miles have you done 73k? have you ever had the chain replaced or is it still the original one?

 

[irmerm]

Original chain. But: If the car was running one evening and then not even firing the next day, timing chain stretch seems unlikely. Even with the timing off a few degrees, the car should still at the very least attempt to fire. I'm not getting any spark at all. Now I'm doubting my diagnosis per PM from member above and considering taking a closer look at the crank sensor. It just doesn't make sense that it wouldn't throw the crank sensor code if that's indeed the issue

 

[irmerm]

Here's my homemade scope pix and vid:

 

[spikester603]

wow!

I would know where to start in making my oscilloscope??

good luck man, hope they do it under warranty.

 

[irmerm]

I was going to test the crank sensor with the scope last night, but I got rained out. So the car is still just chillin' in my driveway. But at least it's clean now. I also re-installed the stock UICP, just to avoid any questions.

 

[irmerm]

tested crank sensor, tested fine. Very pretty wave on the scope, looked like this screenshot I found elsewhere online:

So, Monday the car will definitely be towed to the dealership, since I'm operating on the assumption that the motor is fine mechanically and so it has to be an electronics issue, hopefully the ECM so it'll get replaced, warranty style.

 

[Ev0_j0e]

have you swap ECM with another vehicle?

 

[irmerm]

have you swap ECM with another vehicle?

I have not. I thought there's some reprogramming that has to happen for it to actually work. Even if not, I'm pretty much done troubleshooting at this point and will for sure be taking it in on Monday.

 

[irmerm]

Car is at the dealership now, was towed there yesterday. I am waiting to hear from them. Here's the video of me testing the crank sensor with my homemade oscilloscope.

 

[spikester603]

After even having a dream about this last night...lol...no shit! Cos Ive been calling all my mates for sollutions etc.. sitting there on Xmas day thinking about your problem and what could it be etc!! lol

Im gonna PM my tuner on MLR for you.

Just a thought have you checked the power amp thing that supplys the spark to the coil packs??

Im also gonna put a post on UK MLR for you, hopefully someone has experienced this in the past and a simple sollution is available.

spike m.

 

[irmerm]

thanks man, I feel bad if this really is keeping you up at night, lol. The coil packs don't use any special amplifier to the best of my knowledge. I've pretty much hedged my bets with it being a ECM problem based on the diagnostic steps for P0340 in the service manual, and assuming that it's not an issue with the timing. The tow truck guy thought it sounded like a timing issue from the cranking sound, but that doesn't make sense as the car was running fine when it was last parked.

 

[irmerm]

Spoke with the Service Manager a few minutes ago and was informed that the engine has ZERO COMPRESSION on any cylinder. WTF?!? I am at a loss for possible explanations considering:
- Car ran fine when parked
- I removed valve cover and verified that timing chain and cams are intact and turning over as they should when the motor is cranked. How is it possible to lose all compression after the car ran normally? Fuck.

 

[ElementX]

That's really shitty man. Sorry to hear.

 

[spikester603]

Dude its gotta be the timing chain... its jumped a notch or two?? there cant be any other explanation??

No way would you lose all comp on all cylinders at the same time??

have you checked the marks on the cam pulleys line up?

sounds like the chain dude.

 

[irmerm]

I didn't check the marks when I had the valve cover off, though once I get the car back I plan on doing so. It's starting to cost me some money now which sucks cuz I'm pretty much tapped out following Xmas shopping. The dealership quoted me 3 hours of labor to do an investigative teardown, which I declined. I'm trying to put together a cost effective plan now to get the car towed back to my house (52 miles) so I can do the teardown and any repairs myself. Sigh.

 

[[email protected]]

Highly doubtful that you've lost ALL compression, in ALL 4 cylinders, at the same time. If so, you'd be picking parts of your block up off the street. I can't remember right now to save my life, but Rouge had similar issues regarding the dealership telling him no cylinder pressure.I ended up picking the car up, and it was something simple and the motor was fine.


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