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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N55 Turbo Engine / Drivetrain / Exhaust Modifications > Low charging pressure -> FC 120308 / Long story /
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      09-16-2018, 11:00 AM   #1
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Drives: 2012, 335i
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Low charging pressure -> FC 120308 / Long story /

Hello guys,

So I've been getting a Drivetrain message, on diagnostics there's a fault code 120308 - Charging pressure control, plausibility Pressure too low
N55, 335i 2012 225kW, manual; 150 000 km on the clock

Full Story:
I had a faulty Valvetronic (135608 - Valvetronic, no movement detected; 133E10 etc..), got replaced in BMW

Then I got trouble with HIGH charging pressure (101F01 - Intake pipe absolute pressure, plausibility: Pressure too high) - car was at dealer's for a month or a little more and eventually they ended up with replacing the (I don't know the exact word for it in English) - lever arms and engine hydraulics. Picture attached - see below (these are the old)

Replacing them solved the HIGH pressure fault.

But then I started to get low pressure fault. And there we are today.

I have noticed that my charge pipe was broken so I have replaced it with an alluminium one and everything seemed okay but then I got the drivetrain message again. The same fault occured once again - same 120308. So I started digging deeper.

We have learned that the problem doesn't occur when I drive really agrresive and change gears in really high RPM - if I shift at 5-6k there's no trouble. But if I shift 4th gear in low RPM and go full throttle the fault pops out between 3-4k RPM

We connected the car on the diagnostics to get live data and see what happens -->
On the left there's the aggresive style of shifting in high RPM; on the right there's the everyday drive, shift to the 4th gear and full throttle. (The graphs are from Delphi diagnostics since I am not aware that you can log data from ISTA-D)

I might also have a little oil trouble or maybe a faulty sensor. Sometimes the car asks for 1 litre of oil but if I drive for a while and check the oil level it shows the right amount of oil. There's no blue smoke coming out of the car neither oil leaks were found. So i changed the oil, poured 6.5 liters in and it shows the -MAX- value since then.

We checked the turbo itself and we found out that the wastegate is wiggling a little to both directions. So we will probably try to adjust the screws so it doesn't wiggle (or wiggle a bit less)

So do you have any idea what to do, what else to check...?

Thank you and have a good day guys

Last edited by Drastaa; 09-17-2018 at 02:50 PM.
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