Over boost code solution questions !!!
 

So I'm new to the hhr ss been reading a lot of forums and comments just bought the car runs great other than throwing the P0234 code, so the question when doing a tune or tuner which creates more boost you have to do wide band o2s correct ? So if I did the o2s would I still be getting the over boost codes ? And if so what are good o2s other than the Aem ??? Thanks !!

Welcome to the site! Try plugging P0234 into the search window there are many threads with solutions to your issues of overboost , most point to loose or broken wires, not the O2 sensors

P0234 Turbocharger/Supercharger 'A' Overboost Condition OBDII Engine Light Trouble Code | AutoCodes.com

Does your SS have the GMTU (GM turbo upgrade ) or Stage 1 kit as it's commonly called.
If so, check the wire splices at the upper and lower Tmap connections.

No it's completely stock with 90k miles im leaning towards the wastegate im hitting around 20lbs-23lbs what should stock be hitting ? Want to do the stage kit, would that solve the problem where I wouldn't have to change the wastegate for less boost ? Been reading also that if I do the stage kit have to have it tuned also can't just plug and play ?

20-23 lbs. sounds just like the GMTU or another tune. Any chance the former owner had it tuned but didn't pass that on when it was sold ?
If it has the GMTU, it will have a sticker inside the fuel door that says : Premium Fuel Required
The stock sticker would say : Premium Fuel Recommended
Stock numbers are generally in the 14-17 range depending on the variables such as elevation.
Mine was around 14 stock. 19 when I got the GMTU.

The GMTU kit is not a plug/play. It's just the 2 Tmap sensors and some stickers. The new tune is then downloaded by the dealer and is a VIN specific upgrade to the purchased kit.

I'll check for those ! I don't know the previous owner bought it off a lot... If it had the tune and the 2 tmap sensors it wouldn't throw a p0234 code though under full throttle right ? Where do I go from here ? What can I do to stop the code and limp mode, it's frustrating lol

Everything I have looked at looks stock and the fuel door says recommended, do you think the spring in the wastegate worn out giving me a higher boost ?

Very possible!

May be the bypass valve sticking ? Or the vacuum line to it is off or broken. Easy to pull and check. Only a spring and rubber diaphram. (honestly. It's a little tricky to get the tools to it. 10mm socket on a 1/4 inch drive setup worked for me )
Here's a link with some pics: https://www.chevyhhr.net/forums/how-...acement-43763/

Thank you ! Looks like I have some trials and errors to try and hopefully fix the issues ! Thank you everyone for the input !