[MJayN]

I am posting this to help anyone who might be dealing with this on their N55 engine, as it took me a long time to get this resolved.

First, I have gone crazy for a year trying to find the exact scenario that I've had, but haven't really found it.

Mine started about about 15 months ago. Had about 107K on my F25 (n55). Returning on a long trip (230 miles/4 hours each way) from my home, threw a "Drivetrain Error" on the highway. No loss of power felt. Drove about 45 minutes to my exit to get off the highway (since it seemed to be running fine), then stopped, restarted the car. Error went away. Over the next few weeks, it threw once or twice more. I got the Schwaben ECU reader and it had the 120308 error in memory. Cleared it, but it kept coming back (with the chime and the "Drivetrain error"). Never lost power when it came up.

Replaced the pneumatic wastegate actuator (fairly easy job, but angle is a PITA). No luck. Replaced all vacuum hoses, no luck.

At 108.5K, engine failure (unrelated to 120308 and a whole other story (spun bearings on cylinders 3 & 4) ). New long block engine, which added a new turbo and a new metal charge pipe.

Got it back and it was still throwing the 120308 after a few days. I knew since the CP, turbo and block were new, it had to be a part that wasn't replaced or something broken/misconnected during the engine replacement. Replaced some plastic vacuum piping that looked suspect or had broken connectors (others had mentioned that those parts fixed their 120308, or I felt that they needed replacing at 109K+ miles).

Finally, I replaced the diverter valve, as I had suspected it might be a cause, but was reluctant because it is beyond a PITA to remove and replace. I was never so happy to see a broken part as I was when I finally got the DV out of the turbo.




The rubber membrane was ripped about 1/4 to 1/3 of the way around. It was bad enough that it makes me wonder why it didn't throw 120308 or other errors more often.

I had ordered the GFB (Go Fast Bits) DV upgrade and was greatly helped by this video https://www.youtube.com/watch?v=dQYhu13pLu4. Install took about 4 hours, slowed by the fact that my broken DV was mounted with Torx screws instead of Allen screws, which I guess happened when the block/turbo was replaced.

I took it for a drive long enough to get it to throw the error and tried the scenario that made it throw the most: In motion at under 3K RPM, push peddle slightly to accelerate (think: don't downshift, but accelerate, as if merging onto the highway or slowly passing a car when making a lane change). Even tried hard acceleration from a stop or single/double gear downshift.

NO ERROR.

The GFB DV gives better peddle response and it now idles and runs generally smother than it did. The part was $150. I would think an indy shop would install it for about $500-600 in labor and faster than I did. BMW would probably be $1K or more and you'd get the original, weak OEM BMW DV instead of an upgrade for the cost.

I hope that this might be of use for you or others who have chased the generic DTMs or 120308 errors.

[e30lover318i]

Great work and information! What year is your F25 btw? Is this an EWG N55?

[MJayN]

Originally Posted by e30lover318i

Great work and information! What year is your F25 btw? Is this an EWG N55?

She is a 2012. PWG. Love it. Got it in late 2016 with 54K on it. Put 54K on her in a little over 4 years, with a few NJ to FL runs to run up the mileage. Comfortable, quick and was typically reliable.

The 120308 was the first real problem I had with her. I wasn't happy that the motor died at 108.5K, but I was pushing it to redline to pass a slow SUV in front of me when it seized.

I'll be keeping her for a bit, since I'm in deep now on a new long block, turbo, PWG actuator, CP and upgraded DV. I'm fine with that, as she still looks great and is now working well.

[e30lover318i]

I also have a 12, I read about the later model n55 having updated rod bearings I guess we got screwed. Whats your theory on your rod bearing failure? Previous owner poor maintenance?

[MJayN]

Originally Posted by e30lover318i

I also have a 12, I read about the later model n55 having updated rod bearings I guess we got screwed. Whats your theory on your rod bearing failure? Previous owner poor maintenance?

Yeah, I've read that the RBs were a problem in the early N55s. (I think I've even read weaker than the N54's.) It could have been the 3 previous owner's bad maintenance (1 was a lease). I don't like to push past 7.5-10K on oil, no matter what the computer says, so she was cared for under my watch.

In the X3, I don't tend to redline, as that is my daily and long haul car. (I have an 07 E93 that is slightly tuned for top down quick/fast fun.) So when she seized, it was one of the few times (<20) I actually pushed it that hard. Most miles were highway and a few slightly spirited runs off of a red light, so I lean towards bad design/weak or cheap parts.

The new LB has upgraded bearings over stock, so it won't be a problem in the next 108K or beyond.

[e30lover318i]

Wow that sounds like how I drive “the one time you beat on it” haha ! Were getting any bottom end noise prior that you could hear??

[MJayN]

Originally Posted by e30lover318i

Wow that sounds like how I drive “the one time you beat on it” haha ! Were getting any bottom end noise prior that you could hear??

Not so coincidently, about 4-6 weeks prior I was chatting with a friend of mine who was outside on the passenger's side and I was sitting in the driver's seat. He said "your engine sounds funny". It sounded fine inside, and he's not mechanically inclined, so I didn't give it much thought. (I kind of wrote it off to the boost leak/AC was running/engine was hot from a long idle.) I don't remember being outside of the car while it was running after that, but I sure remembered his words after it seized.

So, the good news is, I guess there were minor warning signs right before it happened. (With COVID, I am not driving much, so that incident was likely within 150 miles of the seizure.) The likely bad news is, what can you do at that point? (Trade it? Drive very cautiously and preemptively replace the engine? Make it somebody else's problem? )

I've taken to testing my oil at every oil change since an additional $30-$40 bucks is worth some insight (and I'm not driving/changing oil often). Had the first change on the new block and all looks good. My N54 E93 looks really good too for her mileage @ 98K. Blackstone makes it pretty easy and they are fairly quick to analyze and report.

I still love the X3, not so much the original N55, but I think with the upgrades, it's a good engine and package. Being somewhat mechanical and willing to work on it myself makes it bearable (and fun) to own. I could have done without the engine swap and DV problem, but glad we have these boards and Youtube as a source of information.

[pungo]

For most instances of bearing failure, the issue is caused by a lack of lubrication. Whether it’s an extended time between oil changes, using the wrong spec oil and or running the engine hard when cold.
10k-15k mile oil change intervals is not uncommon
Higher power tuning amplifies the wear. It's not uncommon for people to put a high stage tune on their vehicle at 100k+ miles without even knowing the true history of the engine. There are plenty of early N55 engines with excess of 200k miles with no rod bearing issues, proven with good blackstone reports.

[MJayN]

Originally Posted by pungo

For most instances of bearing failure, the issue is caused by a lack of lubrication. Whether it’s an extended time between oil changes, using the wrong spec oil and or running the engine hard when cold.
10k-15k mile oil change intervals is not uncommon
Higher power tuning amplifies the wear. It's not uncommon for people to put a high stage tune on their vehicle at 100k+ miles without even knowing the true history of the engine. There are plenty of early N55 engines with excess of 200k miles with no rod bearing issues, proven with good blackstone reports.

I certainly don't doubt there are long running examples of early N55s getting high mileage. I cannot speak to the first 54K on mine, but the last 54K were not neglected or beaten. No tunes, didn't push it when it was cold.

I have read of a few early examples of N55s having bearing problems (under 70K off the top of my head). Maybe they were beaten or not cared for properly. Not common, but I did read of more than one account.

[Beko1994]

Now you got me really scared. I have the same drive malfunction error like you. I have bmw x3 2011 with 101k miles with last 20k miles tuned stage 2+ along with trans tune. I always change the oil around 3k miled and i never floor it before it warms up. Do you thing is smart to replace the bearings before something like that happens? I'm planning on keeping the X3 until 150k miles.

[e30lover318i]

I’ve also read the heat exchanger style oil cooler can fail and contaminate the oil too causing lubrication problems. Normally when the bearings start to go there is a very district tapping. I’ve heard it on other non bmw vehicles many times.

[383vett]

Originally Posted by Beko1994

Now you got me really scared. I have the same drive malfunction error like you. I have bmw x3 2011 with 101k miles with last 20k miles tuned stage 2+ along with trans tune. I always change the oil around 3k miled and i never floor it before it warms up. Do you thing is smart to replace the bearings before something like that happens? I'm planning on keeping the X3 until 150k miles.

No, you don't preemptively replace bearings on a motor with no symptoms. If you do, might as well change rings too. Then it's called an engine overhaul.

[Bdavi011]

I think e30lover has a good point. Many people have experienced engine failure after replacing their OFHG and now everyone recommends to prime your engine after the job is done to ensure oil pressure is present in the engine prior to starting. The idea is that people assumed that somehow the OFHG job caused the engine to run dry for a second or two. However, the OFHG is similar to an oil change. You don't prime your engine after every oil change.

But the root of the problem could be that coolant was leaking into the oil lines due to bad OFHG and oil cooler gasket. It caused damaged and by the time the owner noticed how bad the OFHG got (leaking) and decided to replace but by then it could have been too late. The engines seizes or experiences failure and it is blamed on the OFHG job.

It would make sense as I don't hear about these experiences anymore but did on these forums the past 2 years I have owned my X3. Possibly the early N55s that needed the gasket replacement already had lack of lubrication due to coolant leaking into the oil line, "weaker" bearings, and extended oil changes caused the failures. I am just thinking out loud and can be wrong but I figured it wouldn't hurt to discuss it.

[e30lover318i]

This is a very common similar issue with Mercedes Benz but due to integrated transmission cooler in radiator. I saw a lot of them kill the transmissions torque converter some how, we were seeing cars come in with converter vibrations and over filled transmissions. We scratched our heads on the first few until a customer went to dealer and came back to show us the findings. Converter, radiator, and fluid replacement Solved the issue.

^^^ But like you said about the oil filter, most people don’t prime a filter after an oil change

[MJayN]

Originally Posted by Beko1994

Now you got me really scared. I have the same drive malfunction error like you. I have bmw x3 2011 with 101k miles with last 20k miles tuned stage 2+ along with trans tune. I always change the oil around 3k miled and i never floor it before it warms up. Do you thing is smart to replace the bearings before something like that happens? I'm planning on keeping the X3 until 150k miles.

Are you getting the 120308 (boost pressure too low)? If so, I don't think you have to worry about the bearings (just keep up with the oil changes and get the used oil tested for insight on amount of metal content. This is a good sanity check, since it will indicate a problem if there is one).

If the DTM error(s) is related to boost, you have a vacuum or airflow problem. But the DTM errors could be a ton of different issues. Get a code reader or have Autozone, etc. read them for you.

If you are running a Stage 2, you likely are pushing the boost way past one or more of the OEM vacuum/airflow components' capabilities, or they have aged to the point where they need replacement(s).

Did you replace the CP, vacuum lines or DV yet? If not, I'd start there and in that order. CP isn't too bad of a job and relatively cheap. vacuum lines (PWG) are pretty easy and very cheap (common failure with age/mileage). The DV is B**ch, but at over 100K and 10 years old on a Stage 2, it is likely failing or failed. I'd recommend doing that since you run upgraded.

Beyond that, there are many plastic vacuum lines that run across the top of the motor on the front right side of the engine to different areas. They are not cheap for what they are, but all shouldn't be more than $200 for the parts.

Sometimes overlooked, but also make sure to clean your MAF and boost pressure sensors. Cleaners are cheap and there are plenty of videos out there on how to clean them correctly. Plus, if you have to pull them to clean them, you can inspect them for damage, broken/cracked O rings, broken mount points, etc.

I'm not suggesting to just swap parts willy nilly, but first check them for damage, reseat them and replace them if you feel it is needed or if you suspect they are a likely culprit.

I went after mine in an order that seemed to make sense to me, based on what I saw and read, but admittedly passed on the DV until the end, due to the difficulty of the job. Ultimately, it ended up being the cause.

[Beko1994]

Thank you all for your fast reply. Before i tuned the car i replaced the CP, coils and spark plugs. Then after 20k miles i did it again. As far the rod bearings, i just ordered the kit for the oil analysis and i will start from there.
The codes that i'm getting are following:

ACTIVE CODES
120208 - Charging pressure control, plausibility pressure too high.
120408 - charging pressure control: switch off ass consequential reaction.

it's interesting because i just saw that i have inactive code too.

11A401 - Fuel high pressure during fuel injection release: pressure too low

Any thoughs?
Thank you

[MJayN]

Originally Posted by Beko1994

Thank you all for your fast reply. Before i tuned the car i replaced the CP, coils and spark plugs. Then after 20k miles i did it again. As far the rod bearings, i just ordered the kit for the oil analysis and i will start from there.
The codes that i'm getting are following:

ACTIVE CODES
120208 - Charging pressure control, plausibility pressure too high.
120408 - charging pressure control: switch off ass consequential reaction.

it's interesting because i just saw that i have inactive code too.

11A401 - Fuel high pressure during fuel injection release: pressure too low

Any thoughs?
Thank you

....I did a quick search and found this:

https://x3.xbimmers.com/forums/showthread.php?t=1319804

Sounds promising for your situation. I would check the vacuum lines, swap/fix them, clear all codes and give it a test drive. I would try it slowly at first and then if you don't get the error when you normally do, start ramping it up.