An engine code you will likely see that sucks....

[TooMuchBoost]

PO299 Boost Regulation not Achieved - Turbo won't fully boost and typically its intermittent at first anyway.

This is like an engine code that says the car isn't running right...no chit huh? If you view the following thread this is more common than not even on stock TDI's and a common characteristic is the turbo 'limps' out of the blue and you only have power on level road. You don't have any smoke either of any kind.

This happened to me yesterday and after looking at IC and vacuum lines until my eyes bled I believe I'm going to throw a $75 N75 valve at it and see what happens. The vacuum hose coming off the boost regulator on top of the turbo goes to the N75.

Note: You can usually trick the computer by turning the motor on and off.

This is a major PITA but I thought would warn you up front. I talked to a TDI mechanic yesterday and he said he's seen N75 (boost vacuum control valve on the front of the motor) go as early as 50K and as high as 200K with no noticeable pattern.

Here is a good thread on TDI Club of what the causes can be:

http://forums.tdiclub.com/showthread.php?t=127821&highlight=po299

 

[TooMuchBoost]

http://www.dieselgeek.com/Detail.bok?no=351

Here's a link to an N75 (street name aka Turbo boost regulation solenoid/valve if you are shopping for one).

With shipping this place is less than a local VW dealer so I ordered it from him.

Note that the cars still run when the N75 goes bad but you lack power. In my case I have a bit more than stock HP but a stock TDI would be scarey slow.

 

[Timbeaux]

Diesel geek.com huh?

Never woulda guessed LOL

 

[TooMuchBoost]

Diesel geek.com huh?

Never woulda guessed LOL

Sad but true. LOL

 

[philly04passat]

I have a po299 code popping up every time I hit 3000 rpm's. The N75 (diverter valve) was replaced with no improvement. No leaks were found, and the turbo has been checked and it works. I was able to hook up the vacum line directly to the turbo by-passing the N75 valve and the turbo is on overload, which tells me the turbo works. Does anyone have any ideas on what I can check?