2006 Audi A3 2.0 TDI DSG BKD - Limp mode P0299 underboost

[vagman1979]

Hi,

i'm looking for some advice on a limp mode p0229 I get when in 5th/6th gear at around 2200 RPM - the following message is logged each time, I cannot reproduce it in other gears.

16683 - Boost Pressure Regulation
P0299 - 000 - Control Range Not Reached
Freeze Frame:
RPM: 2415 /min
Torque: 240.0 Nm
Speed: 75.0 km/h
Load: 94.5 %
Voltage: 13.83 V
Bin. Bits: 11000000
Absolute Pres.: 2499.0 mbar
Absolute Pres.: 1346.4 mbar

I've checked the turbo actuator, EGR cooler actuator, actuator on the EGR and the black reservoir using a vacuum gauge and they all hold vacuum to 40 psi.
I have vacuum tested all of the small pipes which go into each of the above using the vacuum gauge and there is no leak.

I've checked and put new seals on all of the boost pipes, there was small oil residue near the intercooler connections but these have now gone since replacing the seals.

The car has the black solenoid block rather than the N75 and not sure how to test this as it doesn't look like a serviceable part.

I have swapped the MAP sensor (same part number) with another car and this has made no difference.

I've taken off the inlet manifold, EGR and throttle body, cleaned them even though they didn't look bad.

You can hear the throttle body humm when the car is switched off.

using VCDS the EGR valve, throttle body all work within their tolerances

I've even taken out the catalyst from the exhaust.

There is no play in both sides of the turbo and the arm for the vanes moves freely, you can see this move when removing and putting the pipe from the actuator.

The only thing left is the fuel pump and MAF sensor before I get to the turbo.

I'm hoping someone can point me in the right direction as I seem to be scratching my head at the moment.

TIA

[vagman1979]

Anyone?

[Zener]

Boost leak? smoke test the intake hoses & inter-cooler plumbing etc , split boost hoses not unheard of inter-coolers leaking at the crimped tank ends not uncommon either , ECU cant regulate boost its not seeing i.e under-boost

[stevieturbo]

First step is verify target boost vs actual boost.

Then verify commanded control duty for boost vs target to see if control is actually trying to make it work.

If it is, then get a mityvac or similar, and apply vac to the control actuator to try and manually force it to make boost and see what happens.

If it cannot, could be a turbo issue, leak, blockage etc etc

And vacuum is negative pressure, 40psi is positive pressure.

With the vacuum gauge attached and driving can you see vacuum on the line to the wastegate actuator/vanes etc ? And this should vary as it tries to control boost relative to the wastegate control duty.

[Zener]

You should be able to get the above info from your VCDS realtime display & read the measuring blocks direct

Edited by Zener on Wednesday 11th August 18:30

[vagman1979]

Thank you everyone, I’ve got it booked in for a smoke test tomorrow.

The turbo actuator holds vacuum and moves the vanes arm as you remove and place the vacuum pipe whilst the car is running. Whilst I was doing this, I noticed the actuator on the egr cooler also move as I placed the vacuum pipe close to turbo actuator, this was only repeatable a few times ( 5 or 6) after that the egr cooler actuator didn’t move. I’m assuming behaves like this whilst boost is built up? I tested all of the actuators with a hand held vacuum gauge and all hold good boost.


I’ve attached an image which shows actual v specified live data at the time is goes into limp mode, in this example specified hits 2499 mbar where actual is 948 mbar, the results in the screen shot have been filtered.

This is consistent each time it goes into limp mode.

Although there is no play on either side of the turbo, and the arm for the turbo vane moves very easily, when I moved the arm I was able to slide it out at the same, so as well as it moving freely up and down it also pulls outwards toward the input side of the turbo. Should it behave like this?

If I put my foot down, boost kicks in around 2700-2900 RPM but it does goes some when it kicks in.

[vagman1979]

smoke test came back negative, is there any other recommendations?

[stevieturbo]

You haven't answered my questions...so take it to a mechanic who can test and diagnose properly.

[vagman1979]

Hi Steve,

thanks, apologies, I wasn't able to test what you wrote. The only thing I was able to capture was specified boost v actual at the time is goes into limp mode.

I wanted to ensure that I wasn't overlooking a boost leak so I had it booked in at the local garage who carried out the smoke test and confirmed there are no leaks.

I'm not sure how to test the following:

Then verify commanded control duty for boost vs target to see if control is actually trying to make it work.

If it is, then get a mityvac or similar, and apply vac to the control actuator to try and manually force it to make boost and see what happens.

[stevieturbo]

vagman1979 said:

Hi Steve,
Then verify commanded control duty for boost vs target to see if control is actually trying to make it work.

If it is, then get a mityvac or similar, and apply vac to the control actuator to try and manually force it to make boost and see what happens.

1. Is simply viewing live data or logging and seeing if the ecu is actually trying operate the actuator to make more boost.

2. Is exactly what it says. Get a Mityvac and manually apply vacuum to the actuator and manually try and force it to make boost. If it cannot, then more than likely there is an issue with the turbo itself.

[vagman1979]

update, I had the smoke test done which came back with no leaks. The mechanic took the actuator arm off from the turbo vanes mechanism, the mechanism moved too freely, it felt like it was not connected to anyting.

removal of the turbo confirmed the vanes had seized in the open position and the arm was not connected anything.