Hello, I have a 2008 HHR SS 5 speed. gsm1 with K&N filter. Recently purchased it at an auto auction. At first I drove it around and noticed I wasn’t getting past 5lbs boost and figured it was running on some kind “Limp Mode” because the dic shows a Service ESC and airbag light. Plugged in the scanner and nothing. Check all the tubing for any cracks or leaks that would cause the low boost. Everything seems to be clamped and tight. Drove it around again and in 3rd gear got to around 4500 rpm and finally got a code. P0299 underboost and a pending P2261. Not sure we’re to start first to diagnose the issue. Maybe the BPV is stuck open. On idle the gauge says the vacuum is between 18-20 so that seems normal. Any help is appreciated.

 

Welcome - mmm WHISKEY!!!! Gotta try 40 Creek from Alberta if you can

Check out this thread for a p2261 error someone else encountered - https://www.chevyhhr.net/forums/ss-s...61-code-59833/

 

It is sort of strange; P0299 means underboost and P2261 means the bypass valve is stuck open.

Here is my guess: the charge air bypass valve vacuum tank has a malfunction. Or, the typical Stage 1 problem with the lower TMAP banging on the AC because the installer didn't modify the TMAP mount. Or, the crimp connections from the upgrade have corroded.

 

Welcome to the site, read causes, and possible cures

https://www.obd-codes.com/P0299

 

yes it is strange, actually this morning i got up to about 8lbs which it has never done. i will add though that the car wasnt moved or used in 6 months sitting in the auction parking lot. maybe the BVP is stuck because of non use. i will open it up today and see.

 

I think it opens with vacuum so a cracked vac line could do it. the 2 are related.

 

Just for kicks and giggles look at the wires and connector that are connected to the TMAP sensors to see if they are crimped or not.

 

i will have a look at them tomorrow. It definitely does not have the plug and play. Now when I accelerate and I get those three or 4 pounds of boost I do hear it blow off but not like a normal SS does, kinda sounds weaker.

 

Ok so I checked the diaphragm of the BPV and it looks good. Checked the wastegate actuator and i was not able to move the rod. So I added some WD to the lever and it moves now but is very stiff. I have to use my whole arm strength to even move it a bit. So I called it quits for the day. Then it hit me. The vacuum lines coming off the solenoid that is attached attached to the intake manifold were routed wrong. The one coming from the charge pipe was going into the intake manifold nipple. The one on the top of the solenoid pointed towards the windshield was coming from the vacuum tank. The one on the left side of the solenoid was going to the BPV (which is ok) and the bottom hose was going into the vacuum tank. So in actually the BPV was never getting vacuum. Would this be a reason for my issue? I feel this would cause overboost and not underboost. I have yet to put everything back the way it should be, but will be making those adjustments later today.

 

Here is the tube diagram, if you need it.