# P0299 - Underboost problem



## JettaJeff1.8t (Jul 30, 2004)

So I recently got a check engine light and VAG-COM said it was a "P0299 - boost pressure regulation control range not reached" code. I've noticed I've been underboosting lately... sometimes it will hit 12-14psi and stick and die off at higher rpm or it will spike to 22psi and hold at 15-17psi like its supposed to and die off which is how it used to act. 
I run APR 93, Eurojet FMIC, and a Forge DV. I heard it could be the N75, N249 valves, boost leaks, PCV, or wastegate control valve on the turbo... no idea where i should go or what i need to do to detemine what is wrong..
I don't believe I have a boost leak because I think this was happening before the FMIC... I just maintenanced the DV today and it seemed fine... 
What do you guys think?


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## FuzzyVW537 (Feb 22, 2008)

*Re: P0299 - Underboost problem (JettaJeff1.8t)*

I would check for a leak but it might also be a failing n75


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## JettaJeff1.8t (Jul 30, 2004)

Do the N75's fail that often though? I have the APR 93 software.. any idea what N75 valve would be better for it? The stock one seemed to work pretty good I didn't get any surging at all... should I go for the race N75 on ECS's site? I forget what part number it is... J or K? i can't remember..
How exactly would I check for leaks? I know that I need to get a pressure test kit where i use an air compressor and fill it with pressurized air but do I just listen for leaks on the hoses?
One of my friends also told me that it could be my PCV system... what should I be looking for with that system?


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## FuzzyVW537 (Feb 22, 2008)

*Re: (JettaJeff1.8t)*


heres my tester, its a 2" schedule 40 PVC Cap with a compressor fitting tapped and siliconed in.

then just insert it where the MAF housing goes.
I set the regulator to 10-15psi and listen for leaks. then feel around the area for exactly where the air is coming from.


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## JettaJeff1.8t (Jul 30, 2004)

*FV-QR*

Alright cool.. this is a graph of my requested vs. actual boost that i logged using vag-com.
Red line is Engine Speed, Yellow is Requested Boost, Blue is Actual Boost
Could my PCV system be causing this? Boost is measured in millibars in vag-com for people that may not know.










_Modified by JettaJeff1.8t at 6:11 PM 5-29-2008_


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## FuzzyVW537 (Feb 22, 2008)

*Re: FV-QR (JettaJeff1.8t)*

looks about right


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## FuzzyVW537 (Feb 22, 2008)

*Re: FV-QR (kaipyroami)*

try to zoom log/graph in 2nd (it looks like) gear from 1500rpm to 5000rpm


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## JettaJeff1.8t (Jul 30, 2004)

*Re: FV-QR (kaipyroami)*


_Quote, originally posted by *kaipyroami* »_looks about right

do you mean it looks like a leak or it looks normal for the code i'm throwing?
i cleared the codes about a week ago and it came back...


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## JettaJeff1.8t (Jul 30, 2004)

*FV-QR*

here is the 2nd gear pull.. zoomed in


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## JettaJeff1.8t (Jul 30, 2004)

*FV-BumpIt(1213371713937)*

anyone?


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## FuzzyVW537 (Feb 22, 2008)

*Re: FV-BumpIt(1213371713937) (JettaJeff1.8t)*

sorry,
it looks like a leak or something.
the actual boost never reaches anywhere near the requested boost.
try checking for a leak first.


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## FuzzyVW537 (Feb 22, 2008)

*Re: FV-BumpIt(1213371713937) (kaipyroami)*

you should be hitting full boost allot sooner than you are.


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## JettaJeff1.8t (Jul 30, 2004)

*FV-QR*

what does a normal graph look like? should it be directly lined up with the requested boost?


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## Jetta4Life (Sep 5, 2001)

*Re: (kaipyroami)*


_Quote, originally posted by *kaipyroami* »_
heres my tester, its a 2" schedule 40 PVC Cap with a compressor fitting tapped and siliconed in.

then just insert it where the MAF housing goes.
I set the regulator to 10-15psi and listen for leaks. then feel around the area for exactly where the air is coming from.
 do you run this with the compressor with the car running or off?


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## FuzzyVW537 (Feb 22, 2008)

*Re: (Jetta4Life)*

to the compressor with the car OFF. 
http://****************.com/smile/emthup.gif


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## wolfsburg1.8Tchipped (Sep 1, 2007)

*Re: P0299 - Underboost problem (JettaJeff1.8t)*

Had the same problem. Replaced the stock N75, with N75J and no problem so far! 14,000k


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## JettaJeff1.8t (Jul 30, 2004)

*Re: P0299 - Underboost problem (wolfsburg1.8Tchipped)*

what kind of chip are you using?


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## GTI_Love777 (6 mo ago)

I like to start with checking the vacuum hoses to see if they are flattened over time as mentioned here in this video 
VW P0299 Turbo Underboost TDI Golf


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## Vegeta Gti (Feb 13, 2003)

Why are you bumping a 14 year old thread with a tdi checklist in a 1.8t forum??

Sent from my SM-N975U using Tapatalk


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