[Billy Weale]

Hello Guys
I have had my BMW M235i 15 reg for just about a year now and is stock however recently i went to drive home after work and Car went into limp when hit boost around 2-3k rpm Causing the drive train error fault to come on no EML. Drivetrain error only comes on when it goes into limp.

I took it to BMW to have it plugged in for readings and showed error fault 120308 - Charging pressure control, plausibility Pressure too low.

The car only goes into limp when hits boost and not before hitting between 2-3k rpm.
If i half throttle it does not go into limp past 3k rpm and seems to be okay only when im full throttle will cause a problem.

I had a technician look at it for about 2 hours and couldn't really fault anything so he programmed it and updated the software as it was still on the software from factory (15) I took it for a road test after and was working perfectly fine (infact better than it has before). However as i went to leave work a few hours later once again it went into limp as it hit boost and had the same problem.

Any ideas anyone?

[n55david]

Check your charge pipe and make sure it's not broken/cracked.. thats the first thing to look at.

[Fedortabak]

So I have to exactly same error and I already replaced my diverter valve and a charge pipe and still no luck and it seem like car is falling into the limp mode since it only shows only up to 160 hp on the sport displays
I've been trying to figure it out for the last year and still no luck
Maybe someone could recommend on what should I do next ?

[BringBackButtons]

What bmw specific codes do you see on your bmw capable scanner?

[Coupsoup]

The code means your measured boost is lower than expected.

Without a scan tool your diagnosis options are limited to taking things apart and looking at them.

Check your charge pipes for leakage like BBB here said. I've seen the CAC tubes pop off the throttle. Check your intercooler for damage from road debris.

If you have a scanner check your boost pressure sensor with the car off. It should read close to 1 bar. Then start the car and graph the data while you drive. Pause the data stream immediately after limp home triggers and check the value.

Honestly there's so much that can be wrong you may just need to find a better tech to check it out if you don't have access to a good scanner.

Holes in the charge pipes
holes in the intercooler
stuck open wastegate
binding or inoperable wastegate actuator
bad boost sensor

Just a few off the top possibilities.

[BringBackButtons]

Just a little more info i can offer on this for a n55 platform....I have found that the boost sensor can get oil in it from an internal leaking vacuum channel in the valve cover. It may be the first sign of valve cover failure ( not just gasket) from heat cycles.

Im not saying its only this as other have mentioned, your map sensor or tmap sensor could also be fouled and now have faulted.

Hope you can get it back in order, no boost is no fun!