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Misdiagnosed balance shaft gear failure

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Old 08-12-2017, 11:49 PM
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Misdiagnosed balance shaft gear failure

So my W211 E350 gave me the dreaded P0016/P0017 codes. I wound the crank around to 305 degrees and sighted the inscriptions through the cam position sensor holes and noted that one was perfectly central and the other was slightly off, not as far off as some of the examples I've seen on youtube, but off none the less.

I pulled the engine out and got the timing cover off only to find the balance shaft gear (all gears driven by the timing chain for that matter) were in excellent condition. There were no signs of wear at all, everything looked like new.

I've not been able to confirm timing chain stretch as the closest to a stretch test I can find is the valve opening relative to the crank angle. I tried to follow the data set out in WIS (no actual procedure provided, just data) but found that it wasn't making sense as the angles were so different that it would be completely impossible to the chain to stretch that far without breaking or causing the engine to not even run

I ended up checking the links around the cam gears and found minimal movement which would suggest the chain has not stretched.

There does appear to be some wear on the chain guides and I was wondering if anyone has had experience with the guides causing P0016/P0017 errors.

Could this also be a sensor issue? I also replaced the magnet on the exhaust cam so I wouldn't expect both P0016 and P0017 errors.

Any thoughts?

Last edited by Splint3048; 08-12-2017 at 11:54 PM.
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Old 08-14-2017, 03:58 PM
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The 305 deg check is a quick test. Did you remove the sensor disks from the cam gear and check the marks on the actual gears in relation to the head. The check is documented in wis. That will indicate chain condition.
I can't recall but does your P codes indicates right bank only?
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Old 08-16-2017, 04:19 AM
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I'm satisfied that the issue is neither related to chain stretch, chain or tooth wear or an incorrect position setup of the gears or sensor disk.

The chain and gears look to be in excellent condition and when I pull the chain tight around the gear there is negligible free movement of the links around the chain. If the links were stretched the first and last links in contact with the gear would engage tightly and there would be some free movement of the other links in contact with the gear.

The markings on both the gears and the sensor disk line up as per the manual, meeting along the mating face of the head/cam cover and the other marks perpendicular to the mating face in the upward position with the crank at 40 ATDC.

I also checked the piston TDC using a dial indicator with respect the TDC on the harmonic balancer, all good.

Given that the base timing is all good, I have some suspicion that the tensioner may not be applying sufficient force to the chain guide allowing the gears to advance slightly due to valve spring forces. The doubt surrounding that theory is that there has at no point been any issues with chain slap.

I also suspect that there may be issues with the sensors. I could swap them around and see if the fault codes follow the sensors. Not sure about the cam adjusters either. The repair kit comes with a new tensioner and magnets, so there is a significant possibility that if I to put it back together all will be ok. If not I'll need to take it to someone with a start tester and look at the live data to try and see what's going on with it.
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Old 08-16-2017, 05:57 PM
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I was thrown for a loop by your post as the balance shaft failure is tied to error codes 1200 and 1208. Glad you're getting it sorted.
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Old 08-17-2017, 03:13 AM
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Originally Posted by kjb55 View Post
the balance shaft failure is tied to error codes 1200 and 1208.
That's right, they can also appear as P0016 and P0017 they mean the exact same thing, I think it depends on the type of code reader you're using. Google M272 balance P0016 P0017 and you'll have a ton of info appear showing the codes relating to balance shaft gear failure.
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Old 08-17-2017, 04:53 PM
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You mentioned at the 305 timing mark one cam lined up perfect the others were off. Which was perfect and which were off? P codes have specific meanings not general meanings. I will look up your specific codes in the morning
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Old 08-20-2017, 09:49 AM
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I unintentionally misled you with regard to one inscription lining up and the other not. They are both misaligned at 305.

I've included a couple of images of the balance shaft gear so you can see the condition is clearly good.






As the front cover was off, I used a dial indicator on the piston crown to find exact TDC. I then bolted a piece of wire to the front of the block and bent it around to align with the o on the harmonic balancer. I then rotated the crank to 40 ATDC and observed the correct alignment on the timing gears.










I then rotated the crank to 305 and noted misalignment of the inscription.










I rotated the crank until the inscriptions were centred through the sensor holes. At this position the crank was at 315.










I then put a dial indicator on the number one intake valve (right bank) and rotated the crank until the valve opened exactly 2 mm. The pointer was in a region of the harmonic balancer which does not give an angle value. I rolled a steel rule around the circumfrence of the area and did a little maths to determine tthe crank position was at or near 56.5. The specs indicate the crank should be at 38.2 which would indicate a stretched chain. I'm a little unclear regarding the value ...1.8. Anyone able to clarify that? Obviously not closing as that is covered further down and cannot be the left bank as that is also covered (not shown), also not a tollerance as the figure of 28.8 is shown further down. Any suggestions?







Even though there is no obvious signs of chain stretch by trying to move the links while held tight over the cam gear, I'm satisfied that the chain is stretched and plan to replace it.
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