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  1. #1
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    P0299 Boost Failure

    2012 e70 35iX (N55 twin turbo)

    Two times now the warning "Engine Malfunction- Reduced Power" has come on and has corrected itself. Tried to use an OBD reader but its clear by the time I get it back in the driveway. I hooked up INPA and in the failure history found a 11351 (P0299) error code, Boost Failure. Doing a search, I found most of these issues with the 335d engine and wastegate failures on the low pressure turbo (N54 engines) or wastegate controller issues.

    On occasion, I will try to accelerate from a slow speed and the X5 feels like its going through molasses for a couple seconds before it takes off. Most times it takes off just fine. I also sometimes get this issue during hard turns and acceleration at the same time.

    Vacuum leaks to the controller can also cause this.

    Anyone had this happen that can start me in the right direction?
    Last edited by kouks; 05-28-2019 at 11:50 PM.

    02 e39 540i Sport (Son), 01 DINAN 7 (Me), 12 e70 X5 x35i (Mrs), 95 e34 525i (Daughter 2), 01 e46 325Ci vert (Daughter 1)

  2. #2
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    I'd start with a pressure converter. That's what BMW calls it. It's the black box on the exhaust side of the valve cover with the vacuum lines. One is source vacuum from the valve cover, the other vacuum line goes to the wastegate.
    ASE and BMW Master Certified Technician

  3. #3
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    Quote Originally Posted by White94RX View Post
    I'd start with a pressure converter. That's what BMW calls it. It's the black box on the exhaust side of the valve cover with the vacuum lines. One is source vacuum from the valve cover, the other vacuum line goes to the wastegate.

    Thanks. Yep, I've found plenty of info on that and the vacuum lines. Makes me wonder, I replaced the valve cover with an OE one due to a bad OSV about 6 months ago, hope the replacement is not causing this.

    Any easy test to check the condition of the wastegate in case its not an easy fix?

    02 e39 540i Sport (Son), 01 DINAN 7 (Me), 12 e70 X5 x35i (Mrs), 95 e34 525i (Daughter 2), 01 e46 325Ci vert (Daughter 1)

  4. #4
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    Hi Kouks, I'm dealing with exactly the same issue....precisely as you described. Car is an '11 X5M, awesome vehicle but this particular issue has been described in various forums, but solution seems elusive. My BMW dealer has taken several attempts at addressing it to no avail other than lightening my wallet....substantially. I just replaced both Pressure converters this afternoon, vacuum lines tested good, reassembled, test drove, accelerating hard from slow speed and keeping foot on throttle sometimes causes this failure, the multi-second delay was still there, and after a few attempts - engine malfunction and limp mode returned. Shutting down and restarting resets it as before.
    So now am going after the manifold pressure sensors. Just now removed the right side sensor - the was oil fouling on the sensor....and that can't be good - laundry list of possible reasons. I'd replaced it with a new one for now.
    Attempting to replace the left MAP sensor......if I could find it. Workshop manuals say to access the left sensor by removing the coolant expansion tank - which I did but not seeing sensor .....and will try getting to it by removing wheel well cover (like right side). Will post again when I have more progress....or not.

    Be glad to hear from anyone who has been down this road.

  5. #5
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    ^well I have the N55 6 cyl engine so it will be different, but if I find it I’ll let you know what I did.

    My first attack will be to change the pressure converter and the vacuum lines. Since one of the lines comes from the valve cover, and I replaced that not too long ago, I’m suspect of that line or the cover itself. The slowing in the turn is a telling sign because that tells me oil shifting around in the turn may be a player, and that again makes me suspect of the cover.

    One other symptom I’m getting is during cold starts, while giving the engine about 30 seconds of oil lube time before I go, the idle rpm will drop and be slightly erratic for a second or two, then back to normal, will do it once or twice per startup. No noticed issue when hot. Acting like a temp vacuum leak?

    It it may be a while until I get to this since it’s so sporadic and does not affect my wife’s short daily drive, plus we’re going on vacation soon, but I’ll post when I get to it.
    Last edited by kouks; 06-02-2019 at 12:01 PM.

    02 e39 540i Sport (Son), 01 DINAN 7 (Me), 12 e70 X5 x35i (Mrs), 95 e34 525i (Daughter 2), 01 e46 325Ci vert (Daughter 1)

  6. #6
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    Had similarsymptoms....sometimes with starting from cold, rpm drops after 5 or 6 seconds(normal), then like you say ~30 seconds later it drops further - rough idle,and recovers. It wasn't always like this. Haven't noticed this in a whilethough.

    So, on my '11 X5M , I have now replaced bothPressure converters, and now both MAP sensors, just took it for a test drive -warmed it up, floored it from a low speed and kept foot on accelerator -hesitant acceleration initially, then it starts to rocket.......and then enginemalfunction - limp mode. Restarting resets it.
    It will consistently do this under hardunrelenting acceleration. So I know at least that it is neither the pressureconverters or the MAP sensors. My shop laptop just died and so I haven't beenable to check if anything different in the codes generated. Need to loadrevtors on a new laptop and check if I can deduce anything new from obd.
    Will post again if I learn anything new. Hopeyou meet with better success than I have had so far.

    If anyone else reading this and attempting toreplace MAP sensors.... accessing the left side MAP sensor on the X5M (S63engine) is ..... very difficult. Manual says access to left side by onlyremoving coolant expansion tank, but it also requires removing the wheel wellcovers, wheel arch trim, and removing a few other pieces to get access. Far more difficult than right side. Tip - Much easier to remove the wheelwell covers first and gain access to the expansion tank connection to radiator,to remove coolant expansion tank. I took a bunch of photos if anyone looking for help tackling this.

  7. #7
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    Sorry to be so late on this thread, but problem solved for me.

    Replaced the Boost Pressure Converter, also found one of the vacuum hoses going to it from the front fender was cracked so replaced that too. Runs great, no warnings or codes. Power is all back.

    02 e39 540i Sport (Son), 01 DINAN 7 (Me), 12 e70 X5 x35i (Mrs), 95 e34 525i (Daughter 2), 01 e46 325Ci vert (Daughter 1)

  8. #8
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    Along with what you replaced did u also change your high pressure fuel pump? Several indie shops swore this would be the fix and it didn't change anything for me

  9. #9
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    A high pressure fuel pump problem will set fuel pressure faults. It may also set boost pressure faults, but for sure will set fuel pressure faults. If you don't have any fuel pressure faults, then I wouldn't even be looking at the HPFP.
    ASE and BMW Master Certified Technician

  10. #10
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    Had more than 1 indie tell me that when they replaced the hpfp that solved the problem. Needless to say I still hve the engine malfunction reduced pressure fault.What u replaced wasn't ever mentioned as a possiblity

  11. #11
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    Well maybe you should take the advice of a professional and replace it?
    ASE and BMW Master Certified Technician

  12. #12
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    Thought the guys I took it to were..lol,but it will be getting changed

  13. #13
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    Quote Originally Posted by MeDerrty4 View Post
    Along with what you replaced did u also change your high pressure fuel pump? Several indie shops swore this would be the fix and it didn't change anything for me
    No, did not touch anything else. You did check all the vacuum hoses going to the Converter right? After I saw the condition of the hose I replaced I may have just gotten away with replacing that for $5 and been OK, but since I already had the Converter I swapped it. I'm keeping the old one as a spare.
    Last edited by kouks; 01-22-2020 at 11:12 AM.

    02 e39 540i Sport (Son), 01 DINAN 7 (Me), 12 e70 X5 x35i (Mrs), 95 e34 525i (Daughter 2), 01 e46 325Ci vert (Daughter 1)

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