r/n55

I have a 2015 BMW 335i N55 EWG tuned on MHD Stage

The car originally had a boost leak at the charge pipe/throttle body connection. I smoke tested it, fixed the leak, replaced the O-ring, and also replaced the MAP sensor.

After fixing the leak, the car feels MUCH better now. Boost and throttle response are stronger and the car pulls harder than before.

But I’m still getting CELs with these codes:

- P12A5 – Manifold Absolute Pressure Sensor “A” After Running Diagnosis Pressure Too High
- P12A4 – Pressure Too Low

Before fixing the leak, I mostly got low pressure codes. After fixing it, I still sometimes get the low code, but now I’m getting the HIGH pressure code more often too.

What’s confusing me is:
- The car actually feels good now
- Smoke test holds fine now
- MAP sensor already replaced
- CEL still comes back after driving for a while

So now I’m trying to figure out what could still cause both overboost and underboost related codes after the leak was repaired.

Could this point toward:
- Wastegate issue?
- Boost control solenoid?
- Adaptation/tune issue?
- Vacuum/PCV issue?
- Turbo problem?

Anyone with N55 experience this?

Is it smart to buy a clean n55 with 88k miles as my first car? 7300 usd . Worried about maintenance cuz i may not have it in budget to maintain it

F30 N55 trackpack retrofit

Hi guys,

I’m trying to understand the full retrofit for the F30 335i Track Handling / Track Package cooling setup, option P337A.

My car is a 2014 F30 335i, and I’m looking at the RealOEM cooling diagrams here:

https://www.realoem.com/bmw/enUS/partgrp?id=3A93-USA-10-2014-F30-BMW-335i&mg=17

The part that confuses me is that there are several different cooling diagrams, and I’m not sure which one shows the complete correct setup for the P337A retrofit. I’m mainly trying to figure out all the parts needed for the extra cooling system, including the driver-side auxiliary radiator, the front auxiliary/transmission cooler area, brackets, air ducts, hoses, pipes, and any smaller mounting parts.

The attached picture shows the areas I’m talking about.

Has anyone retrofitted the full Track Package / P337A cooling system on an F30 335i?

Which RealOEM diagrams should I use, and do you have a complete parts list or checklist for everything needed?

I’d really appreciate any advice from someone who has done this retrofit or compared the standard cooling setup vs the Track Package setup. Right now the diagrams are a bit confusing and I don’t want to miss brackets, ducts, hoses, or small parts.

Thanks!

I bought a 2012 135i vert with an n55 and went around a sharp left turn which caused it to spin a bearing, the oil level was full when this happened. I am currently replacing the engine and was wondering was i should do to prevent this from happening again. Im already replacing the bearings in the new engine. I use the car for cruising and touge around roads with long curves. Shoudl i have to worry about this if i replace the bearings on the new engine?

Hi, I have a 2015 BMW 335i with the N55 engine (EWG) and I’m trying to figure out this persistent code issue.

Before, I used to get both low-pressure and high-pressure MAP/boost related codes, but now I’m only getting this one:

P12A4 — “Manifold Absolute Pressure Sensor ‘A’ After Running Diagnosis Pressure Too Low”

I already replaced the MAP sensor and installed an upgraded aluminum charge pipe.

What’s weird is:
- I clear the code
- car drives fine
- then after around 150–200 miles the code comes back almost every time

I’m tuned on MHD Stage 1. When I log boost:
- target boost is around 14 PSI
- actual boost is only around 10 PSI

The car still feels decently fast, but sometimes throttle feels kind of spongy, especially when the car gets hotter.

Does this code usually mean a boost leak somewhere? Or could it still be:
- bad diverter valve
- wastegate issue
- PCV/valve cover issue
- bad MAP sensor reading
- intercooler/coupler leak

Trying to figure out where to look next before throwing more parts at it.