Getting P0299 Turbo Underboost DTC, No boost leak foud? What to check next?

[drewgold]

So since I have installed my JHM Stage 1 91 Octane tune, I have been getting intermittent P0299 DTCs. Seems to happen most often in 4th gear but I see a significant fade in boost while pulling in third gear.

I checked today for boost/vac leaks and could not find anything. Pressure tested the intake and also used a smoke tester, no leaks were found.

Not sure what to check next? Could this be a sign of a bad wastegate?

I do hear a bit of a whistle sometimes, especially in 3rd gear around 0-8 PSI boost, which would seem to indicate a boost leak, but even at 5PSI with the smoke tester no leaks seen??

Should also mention that I have the latest revision DV, it's about a year old.

Thanks for any help/suggestions.

[Okedokey]

Check your DV again mate. Easiest option at this stage and yes, even after a year, I wouldn't be surprised if its done.

[canadianA4B7]

When I first started my upgrades (s3 K04) the same code came up. Went over the system checked for leaks same thing no leaks nothing was broke over used or anything. Unitronic then revised the tune for a few (baldy I believe was another big influence on them adjusting tune). Next when I went to the 2863, same thing upgraded unitronic tune and code again. Unfortunately this was a pin hole in a weld. There was no smoke exiting the hole, the boost pressure test was run up to 25 psi and that's the only time I cud hear it. And only way I found it was baking soda. Knew the general area tossed some baking soda close to the sound and the stuff went everywhere from the pressure.

If jhm confirms the tune is ok then you've got a leak. It's finding it that's going to be hell.

On this rebuild I back yard assembled the complete engine. I tightened every clamp every but every bolt. So far 100km into this rebuild no codes. Other then the few things I missed plugging in and a knock sensor that was not tightened to spec.

[Vip3r]

Hey.

I actually am going through the same thing as we speak. Installed my JHM stage 1 93 oct tune about 3 months ago. About a month ago I began hearing a metallic chirp coming from the turbo area and my boost was dropping as well. I am just in the process now of figuring out the cause. I also have checked and have no leaks at all. Also DV is fine as well. A buddy of mine, who is a mec is going to take my car this week and take of the turbo and do some inspection. I'll let you know what I come up with. Goodluck, hopefully it's not as involved as mine.

[BKLYNAUDI]

n75 valve Part # 06F906283F

[jamerican1]

Mine was the wastegate...

[drewgold]

Thanks for the responses, much appreciated.

Check your DV again mate. Easiest option at this stage and yes, even after a year, I wouldn't be surprised if its done.

I do have a spare DV so I'll try swapping it out to see it it makes any difference.

When I first started my upgrades (s3 K04) the same code came up. Went over the system checked for leaks same thing no leaks nothing was broke over used or anything. Unitronic then revised the tune for a few (baldy I believe was another big influence on them adjusting tune). Next when I went to the 2863, same thing upgraded unitronic tune and code again. Unfortunately this was a pin hole in a weld. There was no smoke exiting the hole, the boost pressure test was run up to 25 psi and that's the only time I cud hear it. And only way I found it was baking soda. Knew the general area tossed some baking soda close to the sound and the stuff went everywhere from the pressure.

If jhm confirms the tune is ok then you've got a leak. It's finding it that's going to be hell.

On this rebuild I back yard assembled the complete engine. I tightened every clamp every but every bolt. So far 100km into this rebuild no codes. Other then the few things I missed plugging in and a knock sensor that was not tightened to spec.

Where was this pinhole leak? Just curious as manufacturing defects tend to occur in the same spots.
And how were you able to pressurize your system to 25psi? Seems that the air escapes into the crankcase and makes a lot of noise as it gurgles out, making it tough to diagnose any leak sounds.

n75 valve Part # 06F906283F

Is there any way to test the N75? Or specific symptoms to the N75 being bad? From what I have read, a bad N75 would likely cause sudden boost drops or inconsistent boost. In my case, it seems like more of a steady fade of boost or lack of hitting peak boost at WOT. Luckily they're not too expensive so may just try installing a new one.

- - - Updated - - -

Mine was the wastegate...

How did you narrow it down to the wastegate? Did you try the wastegate adjustment? Any luck with that?

[canadianA4B7]

I was told w boost leak tester u can put as much air into it as what your car handles boost wise. I think I was at 22psi when I found it. It was in the custom pipe EPY made for the synapse DV. A piece or 3/4 or 1" pipe had a kick to it he welded along the weld there was just a weld pin hole.

I had replaced most of the Sensors aswell.

This sounds so stupid. When I boost leak test I put a stupid Kleenex box (empty or stuffed w rags tape to hold it in place) over the oil cap opening. Creates a bit of baffle or muffles the gurgle the engine makes when putting air in the system.

This was copy written by redneck engineering in Canada..... Company doesn't exist but if any of you use this idea send Paypal payment of the cost of whatever parts you discover are busted to me directly. I won't legally come after you. $5.00 for beer money is accepted too.

[drewgold]

Update:

So I cleaned my MAF sensor yesterday and so far no code... Fingers crossed but it hasn't been thrown regularly enough to say I'm out of the woods yet.

My MAF was very dirty, the screen was covered in a black residue and I can only assume the sensor was the same. Blasted the sensor with MAF cleaner but not sure how well it cleans things with spray only. May have to look at buying a new one just based on all of the gummy residue on the mesh and MAF housing.

I'm still getting some stumbling under partial throttle in 1st and 2nd gear before the engine is warmed up, so still seems like something is not working properly. May still just replace the n75 for good measure based on it being a failure probe part and already having over 175k kms on it.

[djhemmen]

Update:

So I cleaned my MAF sensor yesterday and so far no code... Fingers crossed but it hasn't been thrown regularly enough to say I'm out of the woods yet.

My MAF was very dirty, the screen was covered in a black residue and I can only assume the sensor was the same. Blasted the sensor with MAF cleaner but not sure how well it cleans things with spray only. May have to look at buying a new one just based on all of the gummy residue on the mesh and MAF housing.

I'm still getting some stumbling under partial throttle in 1st and 2nd gear before the engine is warmed up, so still seems like something is not working properly. May still just replace the n75 for good measure based on it being a failure probe part and already having over 175k kms on it.

Have you tried testing your N75 valve? Since you know you are getting the P0299 I assume you have VagCom? Here's how from Ross Tech:

http://www.ross-tech.com/vag-com/tour/out_test.html

[drewgold]

I did not know you could test it via VagCom, thanks for the tip.
Just tried it though and no luck, test seemed to complete fine. It seems to just be an on/off test so not sure how likely issues would be to come up with that sort of test.

Being as I had the VagCom out, I tried a requested vs actual boost log. (This is the first time I have tried logging something so not sure if it's helpful or not.)
Did 1st-4th normal driving then 1st-3rd under harder acceleration but not quite WOT.



Seems like the requested vs actual values should be closer?
Also is it normal for the actual and requested values to be so different at idle? Sensor issue maybe?

[Okedokey]

Did you end up changing the DV?

[djhemmen]

There's also an N75 duty cycle you can lookup in the same area as the boost logs. That's how I found my N75 to be bad. It would work during the test when there was no load but only worked intermittently under load.

[drewgold]

Did you end up changing the DV?

I have not yet, can't find the spare I have. Will try to get that in today to see if it makes a difference. You really think it could be malfunctioning after a year? (Not even a year, 10 months actually). It's an easy swap so I'll give it a shot.

There's also an N75 duty cycle you can lookup in the same area as the boost logs. That's how I found my N75 to be bad. It would work during the test when there was no load but only worked intermittently under load.

I did log the duty cycle, seems like things are ok, log is for a pull through 1st-4th gears:




And no luck with the MAF cleaning, p0299 code came back this am. Will try to get a requested vs actual boost log of the 3rd gear pull that seems to throw the code the most often.

[Okedokey]

I suspecting a tear in the diaphragm.

[drewgold]

I suspecting a tear in the diaphragm.

I already have the piston type. There is no diaphragm.

[Okedokey]

The piston type can fail to properly close still. My money is on the DV given that everything else seems to check out.

[drewgold]

New DV is in but still getting p2099 underboost code??? VagCom actually lists it as 'Control Range Not Reached' but same code as before.

I actually also got a Boost Pressure Control Valve (N249) P2262 code - Mechanical Malfunction - Intermittent, got it with the new DV but cleared it and it has not come back. Sticky new DV maybe? Weird.

Here's the requested vs actual log for gears 1-4 at WOT for 2nd and 3rd. Please ignore the missed shift coming out of 1st. Amateur hour! Haha.



I'm at a loss, what's weird is if I build the boost gradually, it seems that the boost pressure gets to where it should but if I floor it and go WOT the boost doesn't peak nearly as high as it should and it fades quickly.

[Okedokey]

So in general terms, it is slow to get to boost required and not making it all the way correct? Im starting to think wastegate? Im really guessing though.

[drewgold]

So in general terms, it is slow to get to boost required and not making it all the way correct? Im starting to think wastegate? Im really guessing though.

Yes, boost seems to come on slowly sometimes, especially in 3rd and 4th gears and then also fades quicker than it seems it should.
I had thought about wastegate as well, may have to try the wastegate adjustment. I'm at a loss.

[Luis_Heineken]

Try the High Pressure Fuel Sensor
Located on the fuel rail (06J906051C, confirm fitment)
and
Low Pressure Fuel Sensor
Located on the high pressure fuel pump (06E906051K, confirm fitment)

That same thing happenned to me, plus i replaced the fuel filter too (4F0201511E)

[Okedokey]

Try the High Pressure Fuel Sensor
Located on the fuel rail (06J906051C, confirm fitment)
and
Low Pressure Fuel Sensor
Located on the high pressure fuel pump (06E906051K, confirm fitment)

That same thing happenned to me, plus i replaced the fuel filter too (4F0201511E)

Thats interesting mate, how would that affect the boost?

[drewgold]

Try the High Pressure Fuel Sensor
Located on the fuel rail (06J906051C, confirm fitment)
and
Low Pressure Fuel Sensor
Located on the high pressure fuel pump (06E906051K, confirm fitment)

That same thing happenned to me, plus i replaced the fuel filter too (4F0201511E)

I guess fueling could cause the lack of boost but I'd think that that would throw codes, no?

I'm going to try another intake pressure test as recommended by Jake@JHM, bumping the pressure up a bit. Not very confident I'll find anything but worth a shot to rule out an actual boost leak.

[RakkCity]

I guess fueling could cause the lack of boost but I'd think that that would throw codes, no?

I'm going to try another intake pressure test as recommended by Jake@JHM, bumping the pressure up a bit. Not very confident I'll find anything but worth a shot to rule out an actual boost leak.

I had a 0299 code that stuck through a new DV, PCV, and all new intercooler piping. Turns out it was a weak LPFP due to an 11 year old fuel filter. Try logging your duty cycle of the LPFP, it should be <55% at warm idle and <70% during pulls. Maybe a bit more during pulls with a tune on it. I also had the P310B code, though, so it might not be the pump in your case, but it is possible for the ECU to pull boost if it doesn't have enough fuel.

[drewgold]

I had a 0299 code that stuck through a new DV, PCV, and all new intercooler piping. Turns out it was a weak LPFP due to an 11 year old fuel filter. Try logging your duty cycle of the LPFP, it should be <55% at warm idle and <70% during pulls. Maybe a bit more during pulls with a tune on it. I also had the P310B code, though, so it might not be the pump in your case, but it is possible for the ECU to pull boost if it doesn't have enough fuel.

I'll give it a check, never know but my HPFP is only a year old and the fuel filter was replaced just after that. I'd hope that my HPFP hasn't already started to die! I guess it could possibly be sensors going bad though....

[RakkCity]

I'll give it a check, never know but my HPFP is only a year old and the fuel filter was replaced just after that. I'd hope that my HPFP hasn't already started to die! I guess it could possibly be sensors going bad though....

I'm talking about the in tank pump, the low pressure one. HPFP would be a different code.


Sent from my iPhone using Audizine mobile app

[drewgold]

I'm talking about the in tank pump, the low pressure one. HPFP would be a different code.


Sent from my iPhone using Audizine mobile app

Ah, thanks for pointing that out. Getting too late, haha.
LPFP is original so I'll definitely log the duty cycle to check it.

[deusilan]

Ah, thanks for pointing that out. Getting too late, haha.
LPFP is original so I'll definitely log the duty cycle to check it.

Any updates? Have you checked your LPFP?

[Gerblack]

So my car went into limp mode after a long idle in 15 degree weather I thought the turbo was gone got it check a the mechanics came up with a 0089 Low fuel pressure and 0299 N249 Turbo Valve and needs reflash PCM. Nobody could do the reflash but the dealership so I started searching audizine and saw that I either needed a new DV, PCV, N75 or wastegate/new turbo. I did the oil cap check so with seemed to rule out PCV I ordered a DV the new revision D one and was going to hope that fixed it. I already bought a used turbo (30K on it from someone who upgraded to a K04 right away) it has been sitting in my garage waiting for this day lol. Well I cont reading different post on here and come across a guy so says disconnect the battery for 5 min and it will clear faults then go from there, I do this and it has cleared all my faults so far. I have only done one test run running up and down the road but the turbo is now boosting just fine and the car is acting right. I will update if the issues return but hopefully i can get a few more miles out of that turbo already has 150K on it.

[esandes]

i had the same code come up once before. the dealership said i needed a new turbo. lol

i cleaned the air filter and the code never came back. the filter was filthy.