One code down: P1515. Another one up: P2272

[MBellRacing]

I have had my 2006 4.8iS for a little over a year now, and **fingers crossed** I finally solved the P1515 "Engine off timer plausibility" code that multiple BMW service places, including the dealership, couldn't figure out. The dealership literally told me that I had "some nonsense code that they can't address". On another BMW forum, I found someone saying that an old battery can somehow cause that issue. Since I have no idea when it was last replaced, I threw a new Interstate at it. A week into a new battery and no P1515! We'll see if that has permanently solved the issue or this thing is just being a mid-2000's BMW and waiting for an inopportune moment to throw it back at me!



Speaking of inopportune, literally the morning I'm driving the car in for state inspection, I get another Service Engine Soon light. I pull over to check the code and it reads P2272 "O2 sensor signal biased/stuck lean bank 2 sensor 2". I understand WHAT the code is saying, but should I replace both O2's on bank 2, should I look at the injectors, is there a chance it's a DME issue? Also, which one is sensor 2-- pre-cat or post-cat? Any help would be absolutely appreciated! I would LOVE to have this dashboard free of lights!



...and yes, I searched. Only two posts with P2272 and one never addressed it, specifically. Promising...

[andrewwynn]

Sensor 2 is post cat.

I would swap the post cat connectors to read the real-time values and see if the sensor is reading. Also; reset adaptations may get you a week or more no error code to get an inspection pass while working out the problem.

[MBellRacing]

Awesome, thanks!



Another few details I should mention:


-It has been pretty cold here, the last couple days-- lows of about 20°F (-7°C) and the car ran a little lopey on cold start. Chocked it up to just being properly cold out for the first time since owning this thing.

-I re-calibrated the Valvetronic servos a couple months ago. No real change to the car or drivability.


-The car does smoke if you let it idle for more than about 5 minutes and it is hot.

-I replaced CCV's about this time last year, car still smoked afterward.


So, all those things tallied up, should I be looking for a vacuum or intake leak? Could a CCV be causing a lean mixture, somehow? Should I be looking for something more underlying that ties these issues together? I need a real Dr. House of N62's!!!

[andrewwynn]

The n62 common fault are the CCV "valves"? (Orange diaphragm). You can check for inordinate vaccum by pulling the dipstick while running at idle. Normal for the engine to stumble a bit when you pull but the vacuum shouldn't be crazy high.

You don't mention odometer. N62 will chew through the VSS and I suspect eventually in addition to smoke will allow enough air though to cause lean codes as well.

[MBellRacing]

Originally Posted by andrewwynn

The n62 common fault are the CCV "valves"? (Orange diaphragm). You can check for inordinate vaccum by pulling the dipstick while running at idle. Normal for the engine to stumble a bit when you pull but the vacuum shouldn't be crazy high.

You don't mention odometer. N62 will chew through the VSS and I suspect eventually in addition to smoke will allow enough air though to cause lean codes as well.

That's a great test. I'll check that. I'd be surprised if a CCV problem would cause severe enough lean mixture for the O2 sensor to think it is stuck, right? Could it cause a stumble?



The previous owner said he replaced valve stem seals about 2 years ago. Car currently has 130,000 miles on it. Read a thing on the M62B44 that mentioned valve cover gaskets can cause some funky issues including oil burning due to it sucking in air under vacuum. Anybody heard of this on the N62?

[andrewwynn]

Do a quick vaccum check from oil fill or dipstick. It should be just a little vacuum.


Sent from my iPhone using Tapatalk Pro

[MBellRacing]

Originally Posted by andrewwynn

Do a quick vaccum check from oil fill or dipstick. It should be just a little vacuum.


Sent from my iPhone using Tapatalk Pro

I'll do that at lunch. And sorry, maybe I'm thinking of this wrongly: The N62 has no functional throttle while running, so I should feel NO to little vacuum, right? Am I feeling for too much? What would that indicate? With no airflow restriction before the intake valves, how would I create vacuum?

[andrewwynn]

I always forget n62 no throttle plate. It does create vacuum though something has to pull in the air/fuel mix :-).

[MBellRacing]

Originally Posted by andrewwynn

I always forget n62 no throttle plate. It does create vacuum though something has to pull in the air/fuel mix :-).

Understood, yeah. I get that. It's a more complicated system than I realized. That said, and for future searches, found this explanation (https://www.xoutpost.com/bmw-sav-for...lue-smoke.html) of why a vacuum leak and/or failing PRV/CCV/PCV can cause both smoking and a lean mixture:

A falling piston creates a vacuum in its combustion chamber. The intake valve opens, passing this vacuum state on to the intake manifold. The intake manifold would become a complete vacuum rather quickly if the plate on the throttle body remained closed. However, the throttle plate is typically open, to some extent, as it controls the air portion of the “air/fuel” mixture that keeps our combustion engines...combusting. The vacuum generated by the falling piston allows metered air to flow past the throttle body, through the intake manifold, and into the expanding combustion chamber.

Beyond the throttle body is a tube connected to the Mass Air Flow (MAF) sensor. A sensor that constantly calculates the amount of air being pulled through the air filter, past the MAF sensor, past the throttle body, and into the intake manifold. The MAF is insanely accurate; to the point where using a throttle plate on a cable becomes a laughable, and turbulent, way to control the flow of air into the combustion chambers. Enter active intake and valve timing (for another time). But, the point of this story is to demonstrate that the throttle body, once the car is warm, is not really used to control the amount of air entering the combustion chambers but, instead, it is used to maintain a constant vacuum or “demand for air” from the MAF. It remains open most of the time, especially when the MAF sensor is telling it that it is drawing in a very specific amount of air. The tube between the MAF and the throttle body contains several possibilities for air to “leak,” unmetered, into the intake. This is a problem because the computer expects the specific quantity of air that the MAF told it to expect and any deviation will cause an imbalance in the “Air/Fuel” ratio…this imbalance chemical reaction leads to unreacted fuel being pushed out your exhaust…fuel that could have been propelling you forward (quickly!). The computer can try to compensate…but it cannot measure what it can neither detect nor predict. This source of unmetered air can be air entering through a disconnected or torn vacuum line, a loose hose clamp, or crack, on one of the intake tubes, or the CrankCase Ventilation (CCV) system.

A lot of vehicles use a CCV system has a valve that is held closed at atmospheric pressure and only opens when internal pressure exceeds atmospheric pressure: the PRV is briefly pushed open, releasing the excess pressure from the crankcase, closing, and the mechanical process starts over. Essentially, BMW uses this system as well; however, BMW’s PRVs default to “open” at atmospheric pressure. This is significantly different because the system BMW uses requires a constant vacuum in order for the PRV to remain sealed; where a traditional system remains sealed until there is excessive pressure. Therefore, if the BMW system cannot establish a vacuum (due to a unmetered air entering the crankcase and/or intake); the PRV cannot close and it cannot prevent oil from entering the intake manifold. I assume BMW had an issue with the pressure generated by the alternative system and, instead, chose a system that requires there to be no pressure to be closed and the presence of any pressure is immediately escaped from the crankcase.

BMW uses the intake’s vacuum to draw unmetered air out of the crankcase until the crankcase itself has so little pressure that the weight of the atmosphere can push the Pressure Regulating Valve (PRV) closed. This works great….unless there is a vacuum leak in the crankcase. As explained in earlier posts, the leak destroys the vacuum by equalizing the crankcase’s pressure with atmospheric pressure. The presence of atmospheric pressure, or any pressure, in the crankcase is enough overcome the PRV, releasing it to its default “open" position. This means that a crankcase vacuum leak allows unmetered air to flow past the PRVs and into the intake…it also means that splashing oil has an unobstructed path, through the same PRV and into your intake and combustion chambers.

We typically only see a cloud of smoke after the car has been warmed up and sitting idle for a prolonged period of time. Why? A cold car starts in “open loop,” a startup sequence that runs more or less based on memory, rather than sensor input. After the car is warm and the thermostats start functioning, the car *can* enter “closed loop,” a state where the car runs based on its sensors and less so on memory. The smoke issue tends to arise when the car enters Closed Loop because the Open Loop operation, uses more fuel, more vacuum, etc.. The added vacuum created by Open Loop’s sensor-ignorant operation is typically enough to overcome a typical vacuum leak…allowing enough of a vacuum to exist that the PRV is pulled closed.

Once the car enters Closed Loop operation, the throttle body relinquishes its control of the air flow to the active intake and valve timing. The finer tuned control of the air flow allows us to enjoy more power and better fuel efficiency…but this also means that it needs less air (and less fuel) to produce the same amount of power. Not needing as much air means that the throttle body doesn’t need to create as much of a vacuum…but less vacuum means that the crankcase vacuum leak can produce enough pressure to hold the PRV open. We typically only see a state of such low vacuum while at idle.

Unfortunately for us, the weak vacuum is still high enough to draw oil into the intake; but not quite high enough to pull the oil around the active intake and into the combustion chambers; at least not until you push the accelerator. Everything behind you disappears…and not in the typical “this is why I bought the V8” euphoria but, rather, a “Go-go-gadget smokescreen” kinda way…the humiliation typically only reserved for those that are lame enough to use go-go-gadget references in their posts. When you hit the gas pedal: the vacuum gets stronger, PRV is held closed, and the oil that made its way into the intake is drawn up and around the active intake channels and directly into the combustion chambers.

SIDE NOTE: The air entering the crankcase contains water vapor from the atmosphere. The PRV is the lone exit from the crankcase; its a very small opening leading to the intake manifold, the source of the vacuum. This tiny opening forces the water vapor and oil to mix before entering your intake...and some of it collects on the PRV itself. When it gets really cold, this cheese can freeze and seal the opening. The blow-by gases can create extreme pressure and in the crankcase, not being able to escape through the PRV nor through the tiny vacuum leak, the excessive pressure can cause the PRV to tear. When the PRV tears, you hear whistling as even more atmosphere is drawn into or blown out of the crankcase. At this point, you will need to replace the PRVs…but just replacing and cleaning the PRVs will not prevent the same situation from happening again. One would need to resolve the issue of how the air (and water vapor) is getting into the crankcase to begin with: a vacuum leak in the crankcase. The same issue, sometimes to a lesser extent, as the smoke cloud.

This literally is explaining SO much of the issues I've had, including the "cheese" on the PRV. I also wonder if that froze, which is why I'm having so many issues in this weather. I need to get this thing to pass it's inspection in the next few days, but then I think I'm going to dive into some serious vacuum leak hunting. Pray it's not a valve cover gasket.......

[MBellRacing]

Okay... false alarm on fixing the P1515-- sort of. While trying to get my readiness done for emissions, I pulled up the BMW codes on my Foxwell. The SES light is off, but along with now the Bank 2 Sensor 1 O2 sensor showing a failure (ironically not the no longer the Bank 2 Sensor 2 is showing a failure), I still see a 2F80 "DME: System time, plausibility" error, which I assume is the P1515 on OBD-II. This seems to be a pretty rare code, unfortunately, and I no longer blame the dealership. Also unfortunately, it seems this points toward DME failure. I'm also wondering if the DME isn't talking to either bank 2 O2's. So... at least a $400 repair at someplace like the-ecu-pro.com. Damn it.


If somebody has a recommendation of what else this could be, PLEASE chime in.



Are you guys ever threatened to set your POS Nazirocket on fire? I am close. I should have bought a soulless Toyota.