RE: lost boost

[yourloveismydrug]

downloaded a vcds lite and finally got a fault code

P1557-35-00  17965 charge pressure control . positive deviation

is this likely to be my  Valve for Boost Pressure Control (N75)??

I have not messed with any pipe work and it is fine now so cant see it being a split/loose pipe

[yourloveismydrug]

took it for a run this morning after clearing the fault code,  managed to get it to happen again ,

uphill , accelerating hard in third , changed to fourth and then limp mode .

stopped reset it and then couldn't get it to do it again .

how can I test the N72 valve , will have a look at the actuator this evening

[Rhyso]

Could be sticky turbo vanes 

[yourloveismydrug]

sort of hoping its not , already asked about anything I can do to clean while in sit

[Agreeable Slick]

Could be many things.

Boost pipes
Vacuum pipes
Boost Pipe clips
Vane mech

Guy I know had a similar problem and it was a pipe had been melted through as the grommit on it had moved and left it rubbing on the manifold.

[yourloveismydrug]

I will of course go through the simplest things first , vac pipes to and from the boost controller , ecu etc

then all the inetrcooler imlet pipes and so on .

she want siliconehoses now anyhoo

[old_n07]

Have a read through this thread, should give you some pointers.

Basically:
Check the vac pipes are connected and not split
Check the VNT actuator arm is moving freely
Check it holds vacuum - if it doesnt the diaphragm inside could be split
Check boost pipes and clips
Check the N75 valve is working - output test in vagcom - this will move the actuator

If all of the above are OK it is more than likely sticking VNT, so log the boost levels and see if you are getting overboost that is throwing the limp mode.

Neil