Turbocharger Byass Valve Circuit Fault

[ansus21]

Hi guys I am a new Audi owner. I just got a 2013 Audi S6 4.0L and car drove fine for a little while, but when I floored it once it started running rough shortly after. I read the codes and Engine module came back with a "P0033" code which said something like Turbocharger Bypass Valve Circuit Fault. Now the car will have issues starting when warm (I need to try starting it three times to even start) and it dies sometimes if I step on the gas pedal. I haven't driven it since this starter happening since I am scared I will blow something up. Another weird thing that I have noticed is that when I undo the oil cap, a strong air suction happens and engine either dies or it runs better (its really weird). If I try putting the oil cap back on (having that the engine hasn't died), engine literally sucks the oil cap shut out of my hand. So I assume something air related is not working right. I honestly don't know where this "turbo bypass valve" is even located and if that has something to do with what I am experiencing. Would any of you know if this is a common issue and what should I look into first? Thanks

[gk1]

P003300 "Turbo Charger Bypass Valve Control Circuit"
Service manual does give much more information than that.
They are the N249 and N427 in this picture. aka "Turbocharger Recirculation Valves"
However I would have someone take a good look at the turbos themselves and if possibly diagnose the PCV health as what you describe sounds like classic signs of a failure.



My understanding of the way the bypass valves function is they close and hold boost while under boost, and release the boost electronically when commanded by the ECM. So, in theory, even if there was an electrical fault with them the car should still idle since it is not under boost at idle, but that is purely a guess. I honestly never tried unplugging one or both and starting the car.

Again, you can start by looking at the bypass valve wiring, but definitely have everything else checked out. Especially if you have not already had the turbos replaced. The 2013 has the highest reported incidents of turbo failure. At least 35%+ by my count.

[ansus21]

Okay so I checked the Bypass valves of Recirculation valves as they are called in that picture for loose connectors or any kind of obvious wiring damage and it looks like I had a loose connector on the passenger side one. I pushed it on all the way and code hasnt come back since it was cleared. However, the car is still ideling rough, barely starting or dying after start when warm. Could you or anyone else show me where the PCV valve is on this car because nothing pops up when I search on youtube/ebay/google. All I have come across are pcv valves for 2.0L.

[qcrazy]

PCV is not real fun...Link

Also, hard warm starts can be a bad HPFP (or less commonly bad injectors). There is a TSB out there for this.

[gk1]

Interesting. You cleared codes after fixing the connection?
Also the connections don't usually just magically come loose. Did you have any work done?
Also, worth re-stating, check your turbos.

RE: PCV...Really?
Tons of info about 4.0T PCVs on this and other forums. Maybe it gets lost by name since it is part of the oil separator.
It is buried in the V.
https://forums.quattroworld.com/s4s6/msgs/346731.phtml
https://www.ecstuning.com/b-genuine-...ly/079103542e/
https://www.audizine.com/forum/showt...arator-R-amp-R

[ansus21]

Yeah I did have some work done to the car. Front end was damaged and I had to replace the front bumper and some parts behind the front bumper. I don't remember undoing the recirc valve connector myself, but it is possible that it has been undone before I got the car (car was damaged before I got it). Yeah, I guess oil/air separator name is a lot more common for this car's pcv valve since I did find a ton of stuff searching by that name. I did clear all codes and none came back. I will probably end up replacing the pcv valve and see if that fixes it. Should I replace anything else while it is all apart? I will also look at the turbos while I have it apart.

[gk1]

Hmmm.... depending on the extent of the front end damage then something else could be the problem. Might be time to think about having someone look it over in detail.