CEL Fun - 16618 / P0234 (Boost Pressure Regulation)

[A4orce84]

Car Background:
2004 Audi A4 1.8T with nearly 220K Miles. Mods listed below in signature.

Hello Everyone,

I recently threw a CEL a few days ago on my B6:

CEL Code:
16618 - Boost Pressure Regulation
P0234 - 001 - Limit Exceeded (Overboost Condition) - MIL ON
Readiness: 0000 0000

Ross-Tech Link:
http://wiki.ross-tech.com/wiki/index...8/P0234/000564

Question:
As I start going through the list of possible root-cause issues listed on the Ross-Tech website, I thought I would post and ask if anyone else has any recommendations on what to check for that may explain why this CEL was triggered?

Thanks in advance to everyone for your time and help, it is greatly appreciated!

[fabric8]

An over boost condition could be caused by the N75 which regulates the wastgate.

Sent from my SM-G950U using Tapatalk

[hightime80]

Or a leaky line to from n75/WG or just a bad WG itself😂

[Hightekflytech]

Or a leaky line to from n75/WG or just a bad WG itself

+1 to all this
When I had that code, it ultimately was a leaky line to the wastegate and a bad n75

[EuroxS4]

Check the n75 also check all the lines coming to it and from it. I have seen the lines split over time from being heat cycled.

[A4orce84]

Hey Everyone,

Just as a mini-update, I was able to finally perform an output test and see if the N75 was functioning properly. I ran through the steps and got the usual clicking as expected. The turbo is a rebuilt K03s using the GPopShop turbo rebuilt kit, performed in 2018. I know some of you recommended looking at the wastegate. Is there an easy way to visibly tell if it is bad / needs adjustment while still being on the car?

Thanks again everyone for your time and assistance so far. It is greatly appreciated! =)

[A4orce84]

+1 to all this
When I had that code, it ultimately was a leaky line to the wastegate and a bad n75

Was there an easy way you were able to determine this was the issue? TIA.

[Hightekflytech]

Was there an easy way you were able to determine this was the issue? TIA.

Hey Everyone,

Just as a mini-update, I was able to finally perform an output test and see if the N75 was functioning properly. I ran through the steps and got the usual clicking as expected. The turbo is a rebuilt K03s using the GPopShop turbo rebuilt kit, performed in 2018. I know some of you recommended looking at the wastegate. Is there an easy way to visibly tell if it is bad / needs adjustment while still being on the car?

Thanks again everyone for your time and assistance so far. It is greatly appreciated! =)

Not necessarily iirc. You would have to inspect the line going to the wastegate for small rips or holes in the vacuum tube. That and pressurize the line going to it with a mityvac or regulated compressor to 5 psi to see if the flap on the wastegate opens

[A4orce84]

That and pressurize the line going to it with a mityvac or regulated compressor to 5 psi to see if the flap on the wastegate opens

But to test the wastegate like you are saying, you need to detach the exhaust or pull the turbo from the car, correct? Similar to how they do it in this video:
https://www.youtube.com/watch?v=Ocqmg6R99qo

Also, even though my N75 was 'clicking' correctly, is that all is needed to determine it is working correctly?

To also add a bit more detail to my issue:
The car tends to be in the 5-10PSi range most of the time. Sometimes, it will boost back to normal levels, ~20PSI since I am chipped, but only for a few seconds and then I'm back down in 5-10PSI land (slightly better than limp mode).

Thanks everyone for your comments and assistance so far!

[A4orce84]

Mid-Week bump! Any feedback would be greatly appreciated.

Thanks!

[A4orce84]

Hey Everyone,

Just to close the loop on this (for anyone looking at this post in the future!), as some of you indicated the root-cause of the issue ended up being a bad vacuum line going to the wastegate. Got a fresh vacuum line installed and the CEL is gone and all power has returned. Definitely better than a bad wastegate that I was mentally preparing to spend a few $$$ on.

Thanks again to everyone for your time and help, it is greatly appreciated!