Codes 121543, 120908, 120408/Charge pressure too low

[LVNXLVSH]

I have a 2017 650i and recently ran into a drivetrain malfunction issue. It first happened a few days ago on Friday night. I parked, let it sit for a couple minutes and restarted it and it was gone and running fine. Two days later i installed the front facing CAI and once i restarted it came back. Again, turned it off, waited, restarted and it was gone. Drove 10 minutes down the street to the store and back, no issues. This morning i went to start it and drivetrain malfunction immediately came on, has not gone away since. I have a jb4 tune (when i checked, it went to map 0 automatically, which i know is a failsafe if that matters) and only run map 2. Onlynother mod aside from what was mentioned above is catless downpipes.

When i read the codes on my jb4 app, its come back with the codes in the picture (sorry if it doesnt load, im new here). The air flow and MAF are always there, because of the jb4 requiring the sensor to be unplugged. The 121543 im assuming is the main code and is causing the other 2. Charge pipes seem to be fine, doesn’t feel or look like there is a leak there. The car idles slightly rough, not too extreme, not all the time. Makes me think there is a leak somewhere? When running a log on my jb4, the turbo is not working at all, it is completely shut off because of the code. Again, im thinking a leak, but also something with the ambient pressure or charge pressure sensor? Been looking everywhere and cant find a straightforward answer or just nothing at all. Any other ideas?

[rorz12]

Originally Posted by LVNXLVSH

I have a 2017 650i and recently ran into a drivetrain malfunction issue. It first happened a few days ago on Friday night. I parked, let it sit for a couple minutes and restarted it and it was gone and running fine. Two days later i installed the front facing CAI and once i restarted it came back. Again, turned it off, waited, restarted and it was gone. Drove 10 minutes down the street to the store and back, no issues. This morning i went to start it and drivetrain malfunction immediately came on, has not gone away since. I have a jb4 tune (when i checked, it went to map 0 automatically, which i know is a failsafe if that matters) and only run map 2. Onlynother mod aside from what was mentioned above is catless downpipes.

When i read the codes on my jb4 app, its come back with the codes in the picture (sorry if it doesnt load, im new here). The air flow and MAF are always there, because of the jb4 requiring the sensor to be unplugged. The 121543 im assuming is the main code and is causing the other 2. Charge pipes seem to be fine, doesn’t feel or look like there is a leak there. The car idles slightly rough, not too extreme, not all the time. Makes me think there is a leak somewhere? When running a log on my jb4, the turbo is not working at all, it is completely shut off because of the code. Again, im thinking a leak, but also something with the ambient pressure or charge pressure sensor? Been looking everywhere and cant find a straightforward answer or just nothing at all. Any other ideas?

It might be completely unrelated to your issue but I recently had a low pressure problem and turbos were not working at all. Turned out because both vaccum pipes from my pressure converters to my turbos had melted (they were resting against the turbo housing) and so the wastegates weren't working. Have you visually checked your vaccum lines to the pressure converters and after the pressure converters? My lines were very obviously broken after looking under the charge pipe with a flashlight. Also, if you have ISTA you can use the service function to do a wastegate actuator test and check if you can see the stems moving.

[LVNXLVSH]

Update:

After a long diagnoses, come to find out it was my jb4 tuner. I replaced it with bm3 almost immediately and all is good, aside from a couple other small unrelated issues that coincidentally came up lol left it unplugged but kept it under the hood. Today I finally took it out, when i lifted it a ton a water came out. Thing got waterboarded somehow. I installed it where BMS recommends to, yet it still happened smh. Anyway, problem solved. On to bm3