Code P0299 "turbo underboost" Resolution Repository

sac48578

Well-known member
Joined
Nov 11, 2008
Location
Folsom CA
TDI
'03 Jetta Wagon
i just had the same problem. Turned out to be the vacuum hose. It cracked right at the plastic support on the firewall. I noticed some of my other cables were getting brittle, so i replaced all the vacuum limes. Takes about 3 meters of hose to replace the smallest diameter hoses. Ran me about $10/meter at the dealership. Just be careful when removing the hose form the vacuum motor for the Anti-shudder valve. I broke the nipple off and i couldn't find anyone who sells a new vacuum motor, everyone wanted to sell me the EGR assembly at about $200. I epoxied a new nipple on and i am hoping it will hold.
 

Harvieux

Vendor , w/Business number
Joined
Aug 15, 1998
Location
Whittier,CA-USA
TDI
06 A5 Pkg.2 w/navi & ASEP
sac48578 said:
i just had the same problem. Turned out to be the vacuum hose. It cracked right at the plastic support on the firewall. I noticed some of my other cables were getting brittle, so i replaced all the vacuum limes. Takes about 3 meters of hose to replace the smallest diameter hoses. Ran me about $10/meter at the dealership. Just be careful when removing the hose form the vacuum motor for the Anti-shudder valve. I broke the nipple off and i couldn't find anyone who sells a new vacuum motor, everyone wanted to sell me the EGR assembly at about $200. I epoxied a new nipple on and i am hoping it will hold.
Not meant as an insult for your attempt to DIYS but, this is another example how valuable professional techs. can be when it comes to the seemingly simple procedures. I can provide many other examples but, I think many here will get my drift.

Next time try using a razor or exacto knife to slit the vacuum line at the barbed nipples to prevent what you experienced. ;) Later!
 

MOGolf

Top Post Dawg
Joined
Jun 27, 2001
Location
underneath something
TDI
2001 Golf GLS TDI Reflex silver, rough road suspension and steel skid plate, 2004 Passat Variant, Candy White, rough road suspension and geared balanced shaft module, and much, much more. 2016 LR RR HSE TD6, 2019 Jaguar I-PACE
sac48578 said:
i just had the same problem. Turned out to be the vacuum hose. It cracked right at the plastic support on the firewall. I noticed some of my other cables were getting brittle, so i replaced all the vacuum limes. Takes about 3 meters of hose to replace the smallest diameter hoses. Ran me about $10/meter at the dealership. Just be careful when removing the hose form the vacuum motor for the Anti-shudder valve. I broke the nipple off and i couldn't find anyone who sells a new vacuum motor, everyone wanted to sell me the EGR assembly at about $200. I epoxied a new nipple on and i am hoping it will hold.
But that's an 03 Jetta. Not even applicable to a B5.5 Passat.
 

05PassatWagonTDI

Well-known member
Joined
Jun 19, 2010
Location
Poulsbo, WA USA
TDI
2005 Passat Wagon TDI
I am kinda confused about what I am experiencing as far as power goes and what is considered a "limp-mode". I do have the PO299 code and the vehicle has no power to pass cars or climb hills. I ended up driving the car mostly on flat ground about 100 miles home @ 70mph. The engine rpms were at 2200 @ 70mph. This didn't seem like the transmission/engine was struggling.......only when I needed to climb a hill or try to pass (no power!)
 

Mechnurse

Veteran Member
Joined
May 17, 2005
Location
Pahrump, Nevada
TDI
97/2K/05/15 Passat 06 Jetta TDI
05PASSATWAGONTDI Have you checked the Turbo outlet hose under the turbo going to the crossover pipe? It tends to leak there and leave a mess, its the seals that can be leaking and causing the P0299 issue. the system is very sensitive to pressure losses and difficult to find the REAL problem. Sometime its a lazy turbo, other times its a cut in the hose or the seals or a vacuum leak. But the car seems to have these issues when your on the pedal lightly. So I had it tuned out to keep from throwing the code. PM me for more info
 

maiorinc

Member
Joined
Jul 26, 2009
Location
Boston
TDI
05 Passat
Fix for my 2005 Passat

I am a newbie TDI owner, but am lucky to live close to Lug_Nut. He was kind enough to give my car the once over for this problem a few months back. We did not find any of the issues lists here. I took a chance and ordered a replacement N75 (at least that's what I think it is), and that did the trick for me. A couple of months now with no problems :).

I bought the part from impex:
SKU: 117576
ITEM: PRESSURE CONVERTER FOR TURBO
COST: $69.45 ea
http://www.worldimpex.com/parts/german-pressure-converter-for-turbo_117576.html

Cesar
 

Biodezl

Veteran Member
Joined
Aug 8, 2002
Location
Davis, CA
TDI
Passat, 2005, Teal; Golf, 1999, Metalic Green, Auto
I chased after a boost underpressure code with a new N75, new MAF sensor, new MAP sensor, new ERG valve, new vacuum hoses and clamps, new boost hose o-rings and clips, new O2 sensor...and weeks of hassle. I finally discovered a boost leak at the upper end of the intercooler. My tardy diagnostic "success" was made possible with the use of UV-fluorescent dye poured into the intake boost hoses, driving around for a day, and then inspecting with a UV flashlight at night from behind the back of the intercooler, with the belly pan removed. The picture below doesn't really show the appearance of the UV-flourecent dye very well (the digital camera may not be able to "see" the dye color), but the greenish circle is in the approximately location where the dye was found in a "spray" pattern. This vantage point is with my head under the front of the car looking up in the space between the windshield washer reservoir (at top of picture) and the back of the intercooler (at bottom of picture).

 

Pklink

New member
Joined
Sep 30, 2010
Location
Colorado
TDI
2004 Passat Wagon TDI
P0101 and P0299

Hello, fairly new owner of a 2004 Passat TDI Wagon. I am getting the same issues as posted on here, however, I don't know all the lingo. Is there a place to go with a diagram that shows all the hoses you are talking about. Also, would a totally clogged K&N air filter possible cause these problems?

Thanks
Paul
 

SUNRG

Top Post Dawg
Joined
Oct 19, 2003
Location
Roanoke, VA
TDI
None currently. Previously owned 04 Golf TDI & 05 Passat GLS Wagon TDI
Hello, fairly new owner of a 2004 Passat TDI Wagon. I am getting the same issues as posted on here, however, I don't know all the lingo. Is there a place to go with a diagram that shows all the hoses you are talking about. Also, would a totally clogged K&N air filter possible cause these problems?

Thanks
Paul
i don't know of a diagram, but yes, i would think a clogged air filter of any type could cause P0299.

fwiw - i personally would not use a K&N air filter. the OEM air filter is excellent - i'd replace the K&N with OEM.
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
ditto on the k&n filter. they are known here on the forum to be bad news.
 

SUNRG

Top Post Dawg
Joined
Oct 19, 2003
Location
Roanoke, VA
TDI
None currently. Previously owned 04 Golf TDI & 05 Passat GLS Wagon TDI
my B5 recently started throwing P0299 and going into limp mode frequently. previously i had resolved this code by replacing a leaking rubber pipe that an electrical wire had worn thru - so i had high hopes that it was just a leak this time too.

unfortunately - it is a turbo failure. 138k miles. or so the dealer claims ...

i'm asking the dealer to replace the o-ring seals on the charge air hoses first, before taking the step of replacing the turbo. i'll report back once this has been resolved.
 
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alvajaalni

Member
Joined
Apr 1, 2011
Location
Maryland
TDI
2005 Passat TDI Wagon GL TDI, 202K, United Gray/Gray Leatherette
I originally posted in this thread (http://forums.tdiclub.com/showthread.php?t=321614), but I suspect this would be the more appropriate area.

I recently pulled the air cleaner box to change the filter. Soon after that was done, the car would sporadically 'limp'. I would restart and everything would seem fine, but within a few days it became more frequent. Then I got the P0299 code.

I looked at all of the lines as best I could without pulling the air cleaner again, and since I couldn't find any leaks I reset the code. Well as soon as I got done and started the car again I got the 'Emissions Workshop' notice and the P0299 code was set again.

Reading through the forums here (GREAT resource :)) I saw a lot if info about the N75 valve and wondered if that may be my newest issue, but it was still very coincidental that it happened soon after I did the air filter change. So today I removed the air cleaner again so I could get a better view of the lines around where I worked and also the N75 valve (not that I could tell much from just looking at it).

I didn't see anything out of order until I looked closer again at the line connected to the turbo actuator. The line had a hole where the connector had worn through the hose. I've opened it up a bit more so it is very visible now, but I didn't see it on my first few inspections.

I'm now looking where to buy new vacuum hose and hoping my issue is just that simple - that is unless I break the N75 valve trying to remove the old hose. :(

I have some pics, but it appears my settings won't allow attachments.
 

KALaBenne

Veteran Member
Joined
Jan 31, 2008
Location
Piedmont, AL USA
TDI
'04 B5.5V GLS
I haven't been on here much in the last few years, but I thought I would chime in on my experiences with this particular problem.
I changed Oil, Air, and Fuel filters this past weekend and when I drove it I had my first experience with limp mode. The car threw an Emissions Workshop warning as well as a check engine light. I don't have VAG-COM so I used a generic code reader on Monday to discover P0299 generic turbo underboost. After researching around here for a bit and reading this thread, I decided to dig and see if I could find the issue. I found one of the vacuum hoses one the front part of the engine below the turbo inlet pipe had seperated while I was yanking on the airbox cover to replace the air filter. I had to remove the the air intake duct (3-phillips screws) so I could get my hands in there to but it back together. The CEL is gone and turbo is operating normally.

Big thanks to the tdiclub!
Gotta drive...
 

Lug_Nut

TDIClub Enthusiast, Pre-Forum Veteran Member
Joined
Jun 20, 1998
Location
Sterling, Massachusetts. USA
TDI
idi: 1988 Bolens DGT1700H, the other oil burner: 1967 Saab Sonett II two stroke
Mine has been fine all summer long. The underboost message re-appeared with cooler mornings of autumn. (hint-hint)
I have now discovered that by using the Frostheater to preheat the car in advance I have had no underboost faults.

No, I STILL haven't located the true cause of my fault, but it's apparently engine temperature related.
 

Richptl

Vendor
Joined
Jan 11, 2011
Location
Apalachin, NY
TDI
2004 Jetta TDI automatic 305,000 miles
A Passat owner near me has been having fits with this issue and has tried about everything. The previous owner used veg oil. A short run with veg oil yields a big build-up on the charge air tubing. So he wants to try my Provent 200
* Could build-up of oil on the compressor wheel stifle its' boost output?
* Could a plugged EGR cooler change the mass flow into the engine? Low EGR means more exhaust to spin the turbo, but then more air to pressurize. Who wins in an uphill, low rpm scenario? Could less EGR actually lower the boost and cause the P0299 code?
 

jarlt

New member
Joined
Jul 19, 2011
Location
Santa Cruz, CA 95060
TDI
2004 Jetta wagon, 2005 Passat wagon
I have taken my 2005 Passat TDI wagon to 2 dealers and 4 independent shops; after smoke test replaced inter-cooler, then a month later N75 and one hose, after second smoke test replaced turbo (ouch), then wire harness. They say they check all hoses and clamps and there are no leaks. Dealer doesn't know for sure but thinks replacing the ECU, $1500, may fix it. Here is the VCDS:

Chassis Type: 3B - VW Passat B5
Scan: 01,02,03,08,15,16,17,19,35,36,37,46,47,55,56,57,58,75,76,77

-------------------------------------------------------------------------------
Address 01: Engine Labels: Redir Fail!
Controller: 038 997 016 T
Component: R4 2,0L EDC G000AG 0314
Coding: 0150034
Shop #: WSC 26030
VCID: 2F1190BFFE13
1 Fault Found:
16683 - Boost Pressure Regulation: Control Range Not Reached
P0299 - 000 - - - Intermittent
Readiness: N/A

Thanks for having this forum
 

pedroYUL

Veteran Member
Joined
Sep 8, 2011
Location
MI, USA
TDI
2015 Passat CVCA; 2015 GSW CRUA; 2012 wagon CJAA; 2004 wagon BEW
Got the code in my BEW jetta.

Solved it by replacing the MAF
 

zindude

Well-known member
Joined
Apr 4, 2010
Location
Paso Robles, CA
TDI
2004 Passat TDI Wagon BS upgrade, EVO skid plate, Koni FSD, Blue euro mirrors, Rocketchip 1+, Euro headlight switch, convience blinker kit(not installed.) 88K
Replaced everything. Now what???

Hello- please help. Was getting "overboost code." Replaced turbo. Now getting "underboost" code. Replaced MAF, Pressure boost sensor, intercooler, N75 valve, cleaned EGR valve and intake throttle. Hoses look good but from what I understand leaks can be elusive. Code is set off both when climbing a small hill at slow speed and cruising at highway speed. Really need to get her back on the road. Any thoughts truly appreciated.
 

Quest4TDI

Well-known member
Joined
Apr 22, 2005
TDI
Passat, '05, Candy White
Got a P0299 code again today in our '05 Passat. Interesting in that the symptoms have been intermittent, and the actual MIL has not indicated any codes. Since this is the second time the symptoms happened, I connected my Scan Gauge II. Even that did not show a Code, but you can then look for what Scan Gauge calls Pending Codes, which is where the P0299 was hiding. That's probably why my MIL indicator never came on.

Happened this afternoon, and clearing the (pending) Code made things run correctly again.

I took an initial look under the hood, but VW sure doesn't make a visual inspection easy, even if you know where to look (not that I do, but I'm reading various threads here to learn). I'd hate to take it to the dealer, but if it takes me too long, I'll have to go that route so my wife gets her Passat back relatively soon.

Our Passat is fully stock, except for the BSM that is. I'll update my post when my problem/solution is found


Herb
 

vanderchevy18

New member
Joined
Jun 23, 2012
Location
Benton, KS
TDI
2004 Passat BHW
I'm having the same problems. I've replaced vacuum lines, n75 valve, sealed intercooler piping connections, and still have the problem. Mine will go to limp mode once every morning. As long as i keep it above 2000 rpms it seems to feel fine but it will still go into limp mode just once a day. I thought i would try a tune hoping it was a programming problem but I'm having an issue with the programmer not wanting to work. Once I get that figured out I'll tune the car and see if it still has an issue. If so its going to Chad Eurotec in Wichita. If it turns out to be an intercooler or piping issue I'm going to build my own intercooler pipes and use some real clamps instead of the total junk VW decided to use. I'll let y'all know.
 

Biodezl

Veteran Member
Joined
Aug 8, 2002
Location
Davis, CA
TDI
Passat, 2005, Teal; Golf, 1999, Metalic Green, Auto
I have been having the same problem for months. Last weekend I replaced the hose between the N75 and the turbo and decided to provide some strain relief at the turbo actuator. Basically I cut a 3-inch piece of transmission oil hose with an inside diameter just slightly larger than the outside diameter of the vacuum hose. I slid the tranny cooler hose over the end of the vacuum hose, firmly attached the vacuum hose to the turbo actuator, then slid the tranny hose down toward the turbo actuator. Looks nice, eh?
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My car would go into limp mode primarily when driving at low loads at the point at which I would slowly start to accelerate. Often this would happen in the morning as mentioned by other posters. The best (worst) example was driving West on I-80 down a hill, and just as the road leveled out while I was still coasting, and as I started to press on the go pedal, poof! No oomph to get over the next hill as several semi-trucks are crawling up my tail!
After a week of driving, no more limp mode!
Why would this work? First, the extreme bend that the hose has to endure has always bothered me. Just seemed like a problem waiting to happen. I figure that since the vacuum is highest when the boost is at zero, this is when the hose is most likely to collapse under the strain of the vacuum. Any small bend or kink in the hose is going to make it more probable to pinch off the vacuum "flow." When the ECU tells the N75 to give more boost (less vacuum) the hose is pinched off and under vacuum. Eventually the hose will open up, but the ECU is too impatient and acts to protect the engine and throws it into limp mode.
 
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Quest4TDI

Well-known member
Joined
Apr 22, 2005
TDI
Passat, '05, Candy White
So BIODEZL, you didn't have any split hoses or vacuum leaks that you are aware of, just the possibility of the hose collapsing due to the combined effects of the vacuum and the bend?

How long ago did you make the line support, and any recurrence of the symptoms?


thanks,
Herb
 

Biodezl

Veteran Member
Joined
Aug 8, 2002
Location
Davis, CA
TDI
Passat, 2005, Teal; Golf, 1999, Metalic Green, Auto
The N75 to turbo actuator hose had some of the cloth braiding worn off, but no signs of cracking or other leaks. Heck, the hose was newly installed a year ago during the post-accident rebuild. That's what made my diagnostic process go so slow... I kept thinking it was something else. Since this fix a week ago I've been purposefully driving in ways that would usually cause the underboost code and limp mode to happen. So far it's like I've got a new car! It now drives like all the diehard B5.5'ers have bragged about. Chip helps too, of course.

P.S. Over the past year and a half, just about everything associated with the the boost control system was replaced including the N75, all vacuum hoses, one-way valve, O2 sensor, MAF sensor, intercooler and other stuff, but not the turbo and the boost hoses themselves. There are no cracks or leaks in the boost hoses, yet.
 
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cspeter8

Veteran Member
Joined
Dec 27, 2007
Location
Central Connecticut
TDI
2004 Passat Sedan
After getting 16683 I found a hole in my turbo outlet hose (the 10" s-shaped hose in lower front passenger side that costs $230, Part# 3B0145828K.. but I cannot figure out how to disconnect the hose from the turbo? Can someone explain what to do with that clip to disengage the hose? It does NOT want to come off. thanks
 

Biodezl

Veteran Member
Joined
Aug 8, 2002
Location
Davis, CA
TDI
Passat, 2005, Teal; Golf, 1999, Metalic Green, Auto
Up until a few days ago, the car was still acting tired with occasional limp mode caused by turbo underboost. Then I discovered the chemical cleaning process in the "Power Enhancements" section and decided to give it a try. You can read more about it here:
http://forums.tdiclub.com/showthread.php?p=4020434#post4020434
Car is back to normal. Here's a teaser photo:


Has anyone else tried this?
 
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travelin77

New member
Joined
Feb 17, 2013
Location
Madison, Alabama
TDI
06 beetle tdi
My 06 beetle did same thing, i found the vacuum hose bundle that runs along top of intake hose had rubbed a hole from the intake hose clamp...looked normal up top but found when turned it over.
 

lavimia

New member
Joined
Dec 31, 2011
Location
san bernardino ca
TDI
2003 jetta tdi
can anyone tell me what the max boost on the bhw mine shows 2400 milbar, is this the stock boost pressure or is this a tuned value??
how can i tell if my car is tuned??
it runs very strong passat wagon tdi 2.0 bhw.
thank you for any responses.
 

spartan

Veteran Member
Joined
Aug 25, 2011
Location
MI
TDI
05 Passat Wagon
I am having the dreaded under boost issue on my newly purchased 05 BHW Passat. I have looked at all of the vaccuum lines, pulled apart and resealed the intercooler pipes (after inspecting them for leaks). I am still getting the code and it is sending me into limp mode, here are details:
-Mainly occurs when going 70+ mph on the highway, on a slight grade (sometimes it will go into limp mode right after a cold start in the AM).
-I logged my requested vs. actual boost while cruising and it is always 200-400 mbar lower than requested. It seems to set off limp mode at more than 500 mbar difference.
-I logged requested vs actual under heavy throttle and the difference does not occur, they are very close to each other.
-I ran an output test on the N75 valve at idle. I read that it was supposed to change the actual boost around 150 mbar during the cycle. Mine did not change at all.

Long story short, should I be looking for a new N75 valve? I am going to run a boost leak test (hopefully tonight) and make sure I don't have any leaks. I have also seen recommendations to swap the N75 with the EGR solenoid as they are the same thing, is this something I should try?

Edit: check your actuator, mine doesn't hold any vacuum at all!
 
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spartan

Veteran Member
Joined
Aug 25, 2011
Location
MI
TDI
05 Passat Wagon
Edit on my post above, spent 6 hours replacing the actuator (without removing the turbo), got the arm moving freely and adjusted correctly, went for a drive success! That is until I got in the car again later and it went into limp mode again going 40 mph :(. I am seriously at my wits end, just bought the car and it has been nothing but problems, to top off the day I found that I have the dreaded torque converter code! I have no boost leaks, a brand new N75 valve, and new vacuum hoses, any suggestions would be awesome.
 

Biodezl

Veteran Member
Joined
Aug 8, 2002
Location
Davis, CA
TDI
Passat, 2005, Teal; Golf, 1999, Metalic Green, Auto
Hey Spartan,
I share your frustration. My wife won't drive the car anymore because of the infrequent, but very unpredictable loss of power due to the underboost code.
We really need a fool proof troubleshooting guide or something that will help us get to the bottom of this.
 
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