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Discussion Starter · #1 ·
I’ve been trying to research this, but I’m having difficulty finding a solution. Recently, my CEL came on and when I checked the code, it came up with P0299, Turbo Underboost. I noticed at the time, that the car did accelerated poorly as if there was no boost. It would still accelerate but very sluggishly. Not that this car is any type of rocket. So, I connected my ODBII and ran the torque app to observe the boost level. I cleared the code and the car seemed to run fine. I was getting adequate amounts of boost when accelerating. But then later the CEL came back on and I lost my boost. When I would try to accelerate, vacuum would go down to “0” but no boost. Funny thing is, I went and cleared the code while I was driving and the boost came back. Then a few minutes later the CEL came back on and the boost was gone. I tried stopping the car, turning off the engine and then turn it back on to see if the boost would come back and it did. I did not clear the code, the engine light was still on, and I had boost.

If it were a vacuum leak, I would think that I would never have boost. If the turbo was broken, it would not be able to produce any boost. It seems as if the cars computer is turning off the boost, but not telling me why it’s doing this. I did clean out my air box and filter. I did a visual inspection of connection. I also disconnected the waste gate actuator to see if the lever mighit be stuck. I sprayed some PB Blaster on it and it seems to swing just fine.

Any ideas why the car is doing this?
 

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Check this video.

 

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Discussion Starter · #3 ·
Yup, I’ve watched all of his videos. I figured it would take some time to zero in on the root cause. I was just hoping if anyone else had the same issue and found the problem, it might point me somewhere more specific. I’ll try to post up what I find. I pray I don’t end up having to replace the entire turbo.
 

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First thing to do is check for leaks by pressurizing the system. I made myself a gizmo when I suspected a leak.





You pressurize to 20 PSI and it shouldn't drop more than 2 PSI in 60 seconds. Mine was leaking a bit and I sealed everything up by tightening clamps and grease. Gained a few PSI.
 

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Discussion Starter · #5 ·
Ordered a boost pressure tester. Also did the corrugated PCV hose modification using better hoses mentioned on the cruzeforum. Checked the flow of the PCV on the turbo connection and it seems to be failing. So maybe that is causing the boost leak, or at least one of them. Ordered a check valve that I’m going to install inline on the hose since it doesn’t seem I can order the connector with built in valve separately.
 

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Discussion Starter · #7 ·
I think I need a bigger compressor. I can’t get the pressure past 18 PSI. However, even at only 18 PSI there is no way it’s holding between 16 and 18 PSI for more than 60 seconds. It pretty much drops immediately. According to the video, it shouldnt’ take less than 20 seconds to go from 20 down to 10 PSI and timing mine, it took about 28 seconds to go from 18 down to 10 psi. I couldn’t hear any hissing so there is no obvious leaks. The highest boost I’ve read driving is about 13 PSI but that is very hard to get to. Most of the time boost is under about 7 PSI. If I have a leak it must be above 10 PSI.

I also checked the wastegate lever again this morning and though it moves freely for most of its range, I did feel it catch at two points. One would be the extreme wide open where it actually sticks in place and has to be jiggled free. I doubt that it ever gets open that far though. The other point seems to be just before being completely closed tight. It’s a slight catch but I’m wondering if that’s what causes the CEL to be triggered.

If I drive gently enough, I don’t seem to trip the code. I went several days after clearing the code without it coming back up. But it I try to trip it and drive hard up long hills, I can get it to come up after about 10 to 20 minutes of driving. Next time it comes up, I think I’ll pull over, pop the hood and see if the actuator is stuck in an open position.
 

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Try moving the 2 nuts on the actuator a couple of turns in favor of more boost, mine had that same catch just before full close. There is no bushing there and grease just gets burnt off. Mine works good lately and see 8PSi regularly.
 

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Discussion Starter · #9 · (Edited)
Thanks Traxy. I tried tightening the actuator arm one full revolution and it does seem to have helped. I’m getting boost more freely and I couldn’t trip the code on my usual test run where I’ve tripped it previously. I’ll have to see how it holds up over the next few weeks.
 

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Same issue PO299 ...I haven't noticed any power change ...they just said car is fine and cleared the check engine light. said bring it back if it comes on again
 

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P0 299 check engine light comes on and lose turbo boost...had it in twice they just reprogram and works for awhile then same thing.....had it to two different dealers..now what?
 

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You obviously have a turbo issue. If it's still under warranty bring it back to the dealer and leave it there, if warranty is out then bring it to a real mechanic, he will look at it with an endoscope and find the problem.
 

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Discussion Starter · #13 ·
My problem hasn’t come back. I checked the pressure, tightened some clamps, loosened the waste gate lever with some brake cleaner and tightened the actuator arm one revolution and the code hasn’t come up again. I’m way past my warranty now so been doing most repairs myself.
 

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Discussion Starter · #14 ·
It’s been a month and the P0299 hasn’t returned. However, I did have the coolant reservoir tank fail at the connector which lead to an engine overheat.

I replaced the tank and the water outlet after finding some coolant seeping around it.

All the while I’ve been getting a P0420 error code. I’ve had it before but I would clear it and it would stay off for a month or more at a time. Now it has narrowed down to popping back up within days or less.

I haven’t found any loose connections or obvious leaks in the exhaust. I’m wondering if exhaust might be leaking out through the wastegate lever. I sprayed break cleaner into it to loosen it up and I wonder if now exhaust might be escaping out through it.

I’ve seen P0420 mentioned before but I haven’t found anyone post a fix. Any suggestions would be appreciated including how to find potential leaks.
 

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2017 Trax here...this seems to be my problem too...just replaced turbo due to code and saw turbo was not working correctly...but now with no check engine lights on...still losing power...car often "chugs" runs fine occasionally..gas consumption has increased...lost at what to check next😔
 

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Check for leaks at intercooler and throttle body. If you live in an area with winters the constant thawing and freezing of moisture at the inlet and outlet of the intercooler causes dirt to accumulate at the bottom between the neck and the hose eventually causing a leak. I just did a 2015 Cruze that was leaking at both and had the same problem at the bottom of the inlet to the throttle body. Cleaned all 3 and added a bit of grease then pulled everything tight. This Cruze had been to the dealer 3 times for P0299, works fine now and guy said he doesn't remember it having this much power ever. His fuel consumption dropped by about 30% too.
 

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Hello, I’m having issues with my P0299 code on my 2015 Buick Encore (I know it’s not Chevy Trax but the people posting seem to have knowledge on what’s going on). I first got the code and pulled the turbo and there was a crack on the inside of the turbo, obviously bad. Then on the way home the light came back on, took it to the dealership and my intercooler had a hole in it. Now every time I turn my AC on the same code pops back up and has cleared itself after a few days in the past. The dealership smoked my lines so there’s no leaks and there’s a brand new turbo and intercooler, what could be the issue??
 

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A crack inside the turbo is fairly normal for these. Hard to get a perfect casting. But this crack would not be enough to give you a P0299.



What part of the turbo did you replace?

Make sure the PCV orange valve is still in the intake.

 

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I had a crack and a hole in the intercooler. Since then I have reset the computer and the check engine light has gone away and it is driving normal. We ordered the Dorman turbo from oriellys, everything that is in that kit got replaced as well as the intercooler.
 

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Here is where the original turbo had cracked.
4027

We have it pulled apart right now, we don’t know which part of the intake the PCV valve is supposed to be, but we found that this hole on the valve cover was blowing air.
4028
 
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