Topic: P0299 (Turbocharger Engine Underboost)

[Gentleman Jack]

Callling all:

I have been trying to help a quiet forum member with a problem.  I have tried all the normal solutions to no boost / low boost problems ie: clamps, IC, tubes etc.  He brought his car in to the dealer and this is the code he pulled and the TSB that goes with it (see below).  I was wondering if this seems to make sense to anyone.  A little background info:  he has aftermarket tune (GMR), intake (fujita) and IC pipes (not sure) as well as a catless exhaust.  He also has a really nice interior, but I am pretty sure that has nothing to do with it    He does have the Tbolt clamps.  Stock IC, but it looks ok from first glance.  Never heard anyone having this code before.  His car has been set up this way for the past 40K miles and just started with this problem after a good hard run with some Vettes.  The TSB is fairly clear in it's description, but before he tries it (or I help him) I wanted to bounce it off of you.  So here it is - copied from a PM he sent me.

Steven,
Greg and the technician (I forgot his name) mentioned that this might not be  the case for my car even the computer said so. They suggested I put everything back to stock, then goes from there.


TSB:

"#09-06-93-004: Intermittent MIL/Check Engine Light On, DTC P0299 or P0234 Set (Adjust Turbocharger Wastegate Actuator) - (Jul 21, 2009)


Subject: Intermittent MIL/Check Engine Light On, DTC P0299 or P0234 Set (Adjust Turbocharger Wastegate Actuator)


Models: 2008-2009 Chevrolet Cobalt, HHR

2008-2009 Pontiac Solstice GXP

2008-2009 Saturn SKY Redline

2008-2009 Opel GT

2008 Daewoo G2X

with Engine RPO LNF and LDK (Europe)

Please Refer to GMVIS




--------------------------------------------------------------------------------

Condition
Some customers may comment that the SES light is on. Upon inspection, you may find DTC

P0299 (Turbocharger Engine Underboost)

or P0234 (Turbocharger Engine Overboost) set.

Cause
This condition may be caused by a mis-adjusted wastegate.

Correction
Note: The wastegate adjustment is sometimes a very fine process. When adjusting the wastegate, only small adjustments should be made. Loosen one nut at a time and only adjust the nut one turn at a time; then tighten the other nut against the shaft and test drive to verify. This may have to be performed several times to achieve the desired boost level. To ensure proper adjustment, the vehicle should be at full operating temperature when testing. The vehicle will be very hot and may need to cool between adjustments. Too large of an adjustment can cause repeat DTCs.

Adjust the turbocharger wastegate. Refer to Turbocharger Wastegate Actuator Adjustment in SI.

Troubleshooting Tips for DTC P0299 - Turbocharger Engine Underboost
To increase boost, adjust the nuts (in) towards the actuator; in essence making the shaft shorter.

Troubleshooting Tips for DTC P0234 - Turbocharger Engine Overboost
To reduce boost, adjust the nuts (out) towards the end of the shaft; in essence making the shaft longer
 

Thanks in advance for any help or thoughts!

GJ
just trying to help mankind one trouble code at a time

[Arabas]

Did he have a wastegate mod?
what about the wastegate spring? maybe the spring got wasted..

[Gentleman Jack]

I don't believe he had ever adjusted his waste gate, but I will check.  The problem only occurs if he drives it hard.  He says it will happen if he goes over 18 psi. if he stops, turns off the car and restarts, its gone.

I will let him know to check out the waste gate spring.

GJ 

[spicy3480]

I was going to suggest checking the little nut on the wastegate adjustment rod.  Sometimes they loosen up and, depending on which direction it moved, can either cause overboost or underboost.  Have your buddy remove the heat shield and take a look at the wastegate nut. 

[Gentleman Jack]

Spicy,
How do we know where it should be?  Is it marked somehow? We can mark a ref point now, but any way of telling prior?

[spicy3480]

I believe there is something like 7-8 threads showing from the nut to the end of the wastegate rod. 

My GF just got this same code in her 2005 Audi 2.0T.  Any ideas there?  Does that car have a wastegate rod also?

[Kelu]

Spicy: 2.0T if that is 2.0 TFSI that engine is very similar to ours. Pretty sure they have a WG too.