Very intermittent misfire/cam code issue - p0390/p0394

[jack28baker]

I thought about this a minute and this is actually an error of the cam position sensor, not the phaser. It’s saying the cam positions sensor isn’t getting valid data, either rpm or position out of range or no or intermittent signal.

Is there anything i can log that would point in a certain direction?

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[jack28baker]

Just did a wiggle test on that sensors wiring, nothing at all. But i do have a theory in my head that makes sense to me at least. Since pac 1234x springs have significantly higher seat pressure (92lbs vs 67lbs from stock). Could it be possible that vct is having a hard time controlling cams during decel/idle where oil pressure is lowest and that sensor is reading it as a fault and putting them into failsafe? I am running 5w30, possibly 5w50 could help if thats the issue? Not sure why it would be so intermittent though but it makes a little sense in my head i guess.

 

[engineermike]

Is there anything i can log that would point in a certain direction?

Yes, the things I mentioned earlier: cam position, desired position, and phaser duty cycle, but they need to be on a very fast data rate. There's no guarantee since it appears as though the errors it's looking for are instantaneous and it adds to the sum each time there's a problem, and when the sum exceeds a threshold you get the code.

 

[engineermike]

Just did a wiggle test on that sensors wiring, nothing at all. But i do have a theory in my head that makes sense to me at least. Since pac 1234x springs have significantly higher seat pressure (92lbs vs 67lbs from stock). Could it be possible that vct is having a hard time controlling cams during decel/idle where oil pressure is lowest and that sensor is reading it as a fault and putting them into failsafe? I am running 5w30, possibly 5w50 could help if thats the issue? Not sure why it would be so intermittent though but it makes a little sense in my head i guess.

When I saw PAC springs that was my first thought, but that's not what the codes are indicating. It's not a desired vs actual mismatch. Mismatch or deviation are codes P0011, 12, 14, 15, 21, 22, 24, and 25. As I explained, your codes (specifically 0390 and 0394) are saying there's a problem with the cam position signal (angle out of range, speed out of range, or lack of signal). It's more of a plausibility check than a deviation check.

 

[jack28baker]

Makes sense, tomorrow I will have my coworker look at it with his snap-on scanner which should be able to look at all that data which my logging software cannot.

 

[jack28baker]

When I saw PAC springs that was my first thought, but that's not what the codes are indicating. It's not a desired vs actual mismatch. Mismatch or deviation are codes P0011, 12, 14, 15, 21, 22, 24, and 25. As I explained, your codes (specifically 0390 and 0394) are saying there's a problem with the cam position signal (angle out of range, speed out of range, or lack of signal). It's more of a plausibility check than a deviation check.

Was able to get a log in forscan of the issue happening, i did basic pid’s then pretty much everything with cam degree attached to it for as much data as possible. The log starts off idling fine at a light and as i start cruising, i can feel it misfiring and then at some point it goes into that fail safe mode. Hopefully it provides some useful data. I can always get more if you need.

 

[engineermike]

I took a look and noticed something a little odd but no smoking gun. Before the exhaust cam ever moved (0% duty cycle) the actual angle varied +/-.5 deg until it was finally commanded off of 0 at timestamp 40591. From that point on, 0% duty resulted in exactly 0 deg angle. That is suspicious to me because I would expect variation of tenths of a degree even at a duty cycle of 0. That said, both exhaust cams are doing the same. May be nothing, though. The misfires didn't start until timestamp 52591, or about 12 seconds after the strange 0 deg cam angle behavior.

If you wanted to continue down this path, I would take everything off of the log except Bank2 exhaust cam desired, actual, duty cycle, VCT2_EXH_F, rpm, and maybe Bank1 actual. That's 5-6 channels. I mentioned in posts 10 to log a minimal number of parameters because more parameters slows the data rate for the ones you really need. This fault is on the Bank2 exhaust cam, so that log has about 20 unnecessary parameters. I'm not sure about forscan, but with PCMTec and VCMScanner, reducing the parameter count along with the logging rate adjustment can get very fast data and you may be able to pick up the cam faults.

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