OK I'm here to revive this post to share some of my experience and find some help.
My car is 2011 335i N55 coupe 65k miles. All stock except a VRSF chargepipe.
Codes that I've already fixed or maybe fixed (the code never pops up but some problems remain) are:
p112f (intake manifold pressure too high)---change cracked stock chargepipe and MAP sensor on it
p325f (plausibility of fuel pressure)---change high pressure fuel pressure sensor
Both codes can put the car into limp mode when I press gas pedal hard, no matter high speed or low speed. Gentle acceleration is fine. No noticeable loss of power. It's been 3 months and 1 month since the 1st and 2nd repair: above two codes never come back.
Now the car got two new codes:
2C57 (charge pressure too low) and
2906 (suspicion of leaks between turbocharger and intake valves). They dont put car into limp mode but a half engine light (disappear after restarting the car). Here is my work on the verification:
- Clear the codes.
- Wide open throttle (WOT) from 0mph to 60mph, no error.
- Cruise at 60mph for a while and WOT from 60mph to 100mph, engine light is on somewhere between 80mph and 100mph
- stop, read codes
I repeated the above process 3 times on 3 separate days, same problem, same codes (2c57, 2906)
I used an Autophix ES910 OBD reader to see the codes and datastream. Online values may fluctuate a little but the trend is firm.
- Ambient pressure: 1010hpa (14.6 psi)
- idle-3k rpm:
- intake manifold pressure after throttle valve: 955.47hpa (13.9psi)
- intake pipe vacuum before throttle value: 1005.23hpa (14.6 psi)
- intake pipe vacuum upstream of throttle valve: 1005.55hpa (14.6 psi)
- 3k-4k rpm:
- intake manifold pressure after throttle valve: 1000hpa (14.5psi)
- intake pipe vacuum before throttle value: 1020hpa (14.8 psi)
- intake pipe vacuum upstream of throttle valve: 1060hpa (15.4 psi)
- 4k-5.5k rpm (above 80mph, engine throws error codes here. No error below 80mph):
- intake manifold pressure after throttle valve: quickly boosted from 1000 to 1400hpa (14.5-20.3psi)
- intake pipe vacuum before throttle value: quickly boosted from 1020 to 1500hpa (14.8-21.8 psi)
- intake pipe vacuum upstream of throttle valve: quickly boosted from 1060 to 1500hpa (15.4-21.8psi)
Here are my questions:
- It looks like code 2C57 and 2906 should show up as twins? I don't know if this 2-code situation is different from the only 2C57 code.
- Stock MAP sensor reads up to 22psi. Stock turbo boosts up to 8 psi. Considering the ambient pressure 14.6psi, the max possible boost absolute pressure read from MAP sensors is about the sensor limit 22psi. My car can boost up to 21.8psi, which looks good. However, there is no boost while cruising (below 3k rpm, MAP sensor reading <= ambient pressure). What are correct MAP sensor readings at different rpms? Anyone share their data?
- If there is boost leak, is it possible that our cars can still get to 22psi? Any suggestions on how to do a quick and easy leak check (not pricey)?
What I will do next, is to change the pneumatic pressure converter mentioned in this post. It is prone to fail so I have to change it anyway even though it still works now. If the problem remains, I will do a thorough leak test and see what is going on. I will keep updating until it is solved (hopefully
). Any comments and supports will be highly appreciated!