u/Dangerous-Radio-8379

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?

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.

I have a 2015 F30 335i N55 and the AC works, but it just doesn’t get as cold as other F30s I’ve owned/driven before.

It blows cold, but not ICE cold, especially on MAX AC during summer weather (~80°F outside).

Things I checked:
- Cabin filter replaced
- Blower fan sounds normal and strong
- Low pressure side was around 40 PSI
- System doesn’t seem empty on refrigerant

One weird thing:
When the AC is running, I hear this “ocean wave” type sound sometimes. Almost like airflow surging/waves coming from the vents or HVAC system.

Anybody know what causes that on these cars?

Could it be:
- slightly low refrigerant?
- overcharged system?
- expansion valve?
- evaporator issue?
- blend door issue?
- weak compressor?
- normal BMW AC behavior?

Would appreciate advice from other F30 owners because I know these cars usually blow colder than this.

I have a 2015 F30 335i N55 that I bought recently. Car is in beautiful shape overall and drives strong, but I’ve got one issue bothering me.

After longer drives, especially once the car is fully hot, I smell a burning smell. Smells kind of like oil burning, but I honestly can’t tell 100%.

Weird part is:
- I don’t see obvious leaks under the car
- Engine bay looks pretty clean
- No smoke from exhaust
- No puddles on the ground

But I did lose about 1 quart of oil in around 1500 miles.

Is that normal oil consumption for an N55, or is something probably leaking/burning somewhere?

Possible things I was thinking:
- valve cover gasket
- oil filter housing gasket
- PCV issue
- oil dripping onto exhaust somewhere hidden
- turbo seals
- or just normal N55 behavior?

Anybody else had this exact issue on an F30 N55?

Body:
Got a 2014 BMW 320i and the driver window completely stopped working.

So far we changed:
- window regulator
- window motor
- master window switch

Still absolutely nothing from the driver window.

We already had a mechanic look at it and he said it’s probably a module issue (FRM/FEM or whatever BMW calls it).

Other windows work fine. Car drives normal.

Questions:
- Is this a common F30 issue?
- Could it still be wiring in the door jamb rubber boot?
- Does the module need coding or replacement?
- Is there a fuse just for the driver window?

And honestly at this point, can we just do some jank ass setup and wire the window motor directly to a separate switch with external power?

Like has anyone bypassed the BMW electronics completely and run:
12V → toggle switch → window motor

Just so the window can go up/down without dealing with BMW module nonsense?

Any advice appreciated before we lose our minds lol.

Body:
Got a 2014 BMW 320i and the driver window completely stopped working.

So far we changed:
- window regulator
- window motor
- master window switch

Still absolutely nothing from the driver window.

We already had a mechanic look at it and he said it’s probably a module issue (FRM/FEM or whatever BMW calls it).

Other windows work fine. Car drives normal.

Questions:
- Is this a common F30 issue?
- Could it still be wiring in the door jamb rubber boot?
- Does the module need coding or replacement?
- Is there a fuse just for the driver window?

And honestly at this point, can we just do some jank ass setup and wire the window motor directly to a separate switch with external power?

Like has anyone bypassed the BMW electronics completely and run:
12V → toggle switch → window motor

Just so the window can go up/down without dealing with BMW module nonsense?

Any advice appreciated before we lose our minds lol.

Body:
Got a 2014 BMW 320i and the driver window completely stopped working.

So far we changed:
- window regulator
- window motor
- master window switch

Still absolutely nothing from the driver window.

We already had a mechanic look at it and he said it’s probably a module issue (FRM/FEM or whatever BMW calls it).

Other windows work fine. Car drives normal.

Questions:
- Is this a common F30 issue?
- Could it still be wiring in the door jamb rubber boot?
- Does the module need coding or replacement?
- Is there a fuse just for the driver window?

And honestly at this point, can we just do some jank ass setup and wire the window motor directly to a separate switch with external power?

Like has anyone bypassed the BMW electronics completely and run:
12V → toggle switch → window motor

Just so the window can go up/down without dealing with BMW module nonsense?

Any advice appreciated before we lose our minds lol.