I have to take the SS in for a P0234 over-boost. Coming home I rolled into the throttle a bit, felt a very slight bump in the engine and noticed the boost was limited to 3 PSI tops on the gauge. I never got an SES light. I scanned it and saw the code. I didn't clear the code (so the dealer can see it) but I stopped, shut it off, restarted and now I have 27-28 PSI of boost which is way too much for a Stage 1 kit (I usually get 20-23 max.)

I did a search and it appears there are a couple of possibilities:

1. Lower map hit the compressor and is leaking at the tube.
2. Wastegate control failure
3. Boost valve failure.
4. ????

I only have 49k on it but the 5/100k ended on 5/31. I am hoping they will still cover it since the failure occurred on 5/28 but I had to head out of town on business. We will see. This dealer is pretty good about getting GM to step up.

 

I'm going to guess its the bypass valve, they don't last too long.

 

Is that the valve that Forge makes a replacement for? Anyone know what fails on them?

 

Yep they make one that is a bypass like the stock one, and a new one that vents to the atmosphere.....I'm running the second one, it goes....PISSSSTTTT !!!

I believe it is the rubber diaphragm that fails. Been a long time, mine failed at 24K, I have 74K now. It most definitely could be a combination of those conditions that are causing your overboost, hopefully the Dealer will find it.

 

Good info, thanks! Yes, I will leave it to them but I love to speculate!

I'm leaning that way to too since the PCM can limit the boost when the code is active (wastegage.)

Terry

 

Yep. It could be this little fellow.

Attachment 14726

 

I do apologize that your car is giving you some trouble. I can look into this issue for you if you private message me your name, address, vehicle identification number, and current mileage. Also what is the name of the dealership you are working with?

Thanks,

Jessica L.
Chevrolet Customer Care

 

Thanks Jessica, I will leave it to the dealer for now to handle. They've been good to work with over the years. The SM didn't think there would be an issue with the power train warranty since it's so close to the end-date but if it's the maps, they aren't covered anyway past B2B. They did the TU install so if it knocked the lower map off, they will probably do something for me. If the turbo valve died, I expect GM to cover it since it's only got 49k on it even if they have to replace the whole turbo for a $100 valve. If GM decides otherwise for 3 lousy days, then I might be in contact! :)

 

That's the valve Forge makes? Is it available separately from the turbo?

 

No. The picture is the stock valve. The Forge unit has an aluminum housing with a screw cap end for easy access to the spring/diaphram.