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Discussion Starter #21
So I had an epiphany regarding the DME's VANOS low pressure errors last night.

The DME has no idea what VANOS pressure really is. None. Not Possible. Having taken apart more than a few now, I don't know why I never realized this sooner. There is no pressure sensor on the S85 VANOS high pressure oil system. If there was, the ISTA/D diagnostic routine for measuring pressure wouldn't have to connect a pressure transducer on the "T" fitting to carry out the diagnosis, it would just poll the DME for the pressure reading.

So, what causes this code then?

It seems to me that the only way the DME would know if pressure was low is if the VANOS actuators were adjusting timing at a slower rate than expected. This would lead the DME to interpret that as low control oil pressure, this triggering the code.

What does this mean?

I had this on my car 3 years ago, only on very, very cold Maine winter mornings. When my injector failed and I opened my bottom end, I replaced the VANOS pump, the high pressure line, the rod bearings, and switched oils. I also replaced 3 of 4 VANOS solenoids before I started the engine back up. This doesn't help in diagnosing at all, but I never saw the error again. I never received it during any summer months before either.

I know the VANOS pump wasn't the fault, I replaced it with a brand new one to upgrade the gears and my old one is running merrily around in another engine for 25k miles now.

It's possible the VANOS HP line was at fault, or I believe more likely is the VANOS solenoids.

It's amazing we (collectively) have never realized/discussed this before. It really has to make you wonder how many BMW techs over the years could have been lead down the path of pump/line replacement when really the solenoids could have been at fault. Often it accompanies two VANOS bank actuator errors and I know they love to replace those.

Just something I figured I should add to this thread. Still trying to work out the mechanics of the error in my head.

A very good addition indeed! The more info we gather, the better off we all are. I haven't seen the error in a while now, not since I've been garaging in a temp controlled environment and keeping the inside temp at around 60F. As long as I don't leave the car for two weeks (happens.. on long trips away), then I don't get the error.


There is merit to what you're saying. A lot, actually. If the oil seeps to the bottom of the block on a long timeline, the VANOS solenoids can be starved of lubrication pressure initially, at the very first crank. Just enough for the DME to try to slam everything to the "Cold Start" position and not get what it asks for immediately causing a CEL.


Either way, I tend to arrange my inspections in the warmer half of the year...
 

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Discussion Starter #22
So I can resurrect my own thread, right?


Some developments after almost four years (and STILL getting this stupid pressure related error):

I didn't drive the car much this winter, got a nice W163 ML truck for that sort of duty now. I let the codes stay lit, didn't reset them, didn't check them. Did flip the bird to the "Increased Emissions" icon a few times after start, I'll admit. But generally I just wanted to see if the issue would go away as the warmer weather falls upon us.

A friend of mine who is a tech at BMW asked me to pull the codes for her, so I did, and interestingly enough I ended up with A FEW. Here they are:

27B6 - VANOS Oil Pressure

271A - VANOS Control Inlet Bank 1

2B25 - Throttle Valve Monitor Bank 1

2B48 - Combustion Misfire with Emissions Deterioration Cyl 7

27C1 - Info Tank leer bei Fehlereintrag (for those who don't "lesen" German, fuel tank ran close to empty and it records this for some German reason.. lol)

277C - Lambda Sensor trim control Diagnostic Bank 1



So a few directly related to bank 1. Recurring ones are the VANOS Oil Pressure code as well as the VANOS Control Inlet Bank 1 code. Usually I just get those in the cold or after sitting for a few days without starting. The others I've never had before, and I would ignore the fuel tank one as a fluke.

So what's going on in bank 1? Does anyone think all of those related codes are suggesting any one thing as the root cause?

Curious to what JColley and B767capt think. I'm still running 10W60 btw, maybe on these 80k-mile engines that weight is doing more harm than good?
 

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In my experience, 27B6 was the code I got and shortly after that, 271B and 271D popped up that got my car in LIMP mode. I ended up replacing the VANOS high pressure oil hoses to fix the issue.
 

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Discussion Starter #24
In my experience, 27B6 was the code I got and shortly after that, 271B and 271D popped up that got my car in LIMP mode. I ended up replacing the VANOS high pressure oil hoses to fix the issue.
So far after clearing the codes the only one to return is the 27B6. This code alone does not throw any emissions or CEL lights. Im guessing it could be a slow leak at the internal line, even though it was replaced many years ago as a recall by BMW. But its odd that the only bank having issues is Bank 1, where as if it were the line bleeding down pressure bot banks should be affected. This is what stumps me.
 

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I’m getting this exact same issue, low vanos pressure code but only on cold start up once initial start code don’t come back till next cold start, did anybody ever get the answer to this fault ?
 
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