P0299 Turbo/super charger underboost

unameiti'lltryit

Well-known member
Joined
Dec 8, 2006
Location
Owen Sound, Ontario
TDI
2003 Golf
The service engine light came on when my wife was driving to Toronto and she said that she was not losing any power but the service engine light would go off and would come on again after a bit. On my code reader the code was P0299 Turbo/Super charger underboost. Any suggestions where I should start looking for the problem?
 

hobbyshop

Veteran Member
Joined
Nov 17, 2004
Location
Toronto
TDI
Jetta TDI Sport, 2004, Platinum Grey
i think i recently got that code yesterday too!

on acceleration, it'd boost.. and then the turbo would cut out, and not much boost would be felt, so drop in power. after a restart, the boost would be back.

it's not as responsive as it used to be. sometimes it wouldn't boost at all, and would get lots of smoke on acceleration
 

Windex

Top Post Dawg
Joined
Apr 1, 2006
Location
Cambridge
TDI
05 B5V 01E FRF
This code can result from an exhaust leak before the turbo. Typically, the only thing that can cause this is a leak on either of the egr pipes, or their associated gaskets.

There is also a chance that the vnt actuator is stuck, either by the vanes being frozen or the diaphragm being ripped, but check for exhaust leaks at the EGR pipes first.
 

hobbyshop

Veteran Member
Joined
Nov 17, 2004
Location
Toronto
TDI
Jetta TDI Sport, 2004, Platinum Grey
i have blocked EGR... soo... vnt actuator is stuck? how do i unstick it. ha
 

Windex

Top Post Dawg
Joined
Apr 1, 2006
Location
Cambridge
TDI
05 B5V 01E FRF
The best way to diagnose a stuck actuator or vanes is with a vacuum pump on the vacuum line from the N75 to the VNT actuator.

Use the pump to pull a vacuum on the actuator, and the actuator should draw in the rod attached to the turbo. The rod and actuator arm should move smoothly and evenly. If not, the vanes are likely sticking. If the rod doesn't move, and doesn't hold vacuum, then the diaphragm in the actuator is ripped, and needs to be replaced.
 

unameiti'lltryit

Well-known member
Joined
Dec 8, 2006
Location
Owen Sound, Ontario
TDI
2003 Golf
I will check the egr pipes and see if I can see anything for leaks. My wife was out with the car today and the service engine light didn't come on and she said the car was working good.
 
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