Hello. I am a new owner of a 2009 HHR SS and I bought it with a problem and I thought it was a easy fix and now I'm a little stumped. I was hoping the community can come by and help me out. I am kind of mechanically inclined i have done some things but nothing super major.
When I first bought the car it had code p2261 bypass valve stuck. Would not make boost past 7 unless it was random then would go back down and made a turbo turbo flutter like a aftermarket BPV/BOF or something was done to it. I thought it would be a super easy fix.. I bought a forge bypass valve NOT VENTED ( I wanted factory feel but with metal not plastic), unplugged battery and then I installed the valve. I went and drove it for about 25 miles and it was so good! I got around 15 psi maybe more. I went to start it about 5 hours later and engine light is on.. now it is down to 7-8 psi on a good pull depending on gear and most of the time its 3 psi.

84k miles
Back round on the car as I know and inspected.
ZZP INTAKE
Has ZZP stuff on the driver side of the block. I have no idea what they are.. I can get pictures if everyone wants.
It does have the factory Gm performace upgrade with LSD and Brembos
It also has GM PERFORMANCE under the hood on a badge/sticker and says premium only in the gas door which from what I have read that is a GM Upgrade to turbo? How do I make sure it is? Is 15 psi too low if it is upgraded?
Car does have a turbo flutter? the stu tu tu tu noise when let off gas at all even if PSI is very very low. I thought again turbo flutter was from BPV so I was hoping forge would stop it.

Went to autozone and code pulled now was P2178 and secondary DTC is p2261.

What I think and I'm not a good mechanic. I believe that the Bypass solenoid is bad and is not releasing the BPV in time? or is that all pressure biased? If pressure is being released into air by the fluttering and not through BPV then it will cause car to be rich under deacceleration?
I did use the weaker of the springs for the forge BPV because I don't think the turbo is building enough boost to use the hardened spring to higher boost pressures.

Please any ideas would be great and I hope I can learn a thing or two about turboed cars and how to fix them. Thank you all!

EDIT I just pulled the Carfax and Map sensor was replaced at 83k miles.

 

The P2178 refers to air fuel mixture, could be the MAF sensor, dirty or the O2 sensor after the catalytic converter could be fuel pressure please read all the article before you buy any parts

https://www.obd-codes.com/p2178

What causes the P2261 code?
Intake manifold vacuum leak
Dirty air cleaner
Wastegate that is stuck open
Wastegate that is stuck closed
Faulty intercooler
Bolts between the turbocharger and exhaust manifold that are loose
Faulty boost sensor
Boost sensor wiring that is shorted or open
Boost sensor reference circuit connectors that are loose, disconnected, or corroded
Turbo failure caused by internal oil leaks and/or oil supply restrictions
What are the symptoms of the P2261 code?
Difficulty with acceleration
Rattling sound coming from the turbocharger and/or turbo pipes
Smoke coming from the exhaust
High engine temperatures
High transmission temperatures
Hissing sound coming from the turbocharger wastegate and/or turbocharger hoses
Loss of engine performance
Unusual boost pressure levels
Fouled spark plug
Cylinder combustion
Other diagnostic trouble codes stored along with P2261, such as boost codes, engine misfire codes, or knock sensor codes
How does a mechanic diagnose the P2261 code?
Inspects wiring and connectors for shorts, burns, and corrosion

Clears the codes and runs the engine (if the P2261 code does not come back, it is an indication that an intermittent problem exists, which cannot always be diagnosed immediately)

Makes sure there are no misfire conditions

Makes sure that the turbo hose clamps are tight

Makes sure that the turbo intake hoses and intercooler hoses are free from leaks and cracks

Makes sure that the air intake hoses are tight and not damaged in any way.

Makes sure that the vacuum lines are not cracked, torn, or disconnected.

While running the engine, gets the RPMs up to 5,000 and releases the throttle (uses a boost gauge to observe boost pressure levels)

If boost pressure levels are above 19 lbs., this is an indication that the westgate is faulty.

If boost pressure levels fall below 14 lbs., this is an indication that there is a problem with the turbocharger or exhaust.

Uses a vacuum pump to see if the wastegate is functioning properly
If an extreme drop in boost pressure is observed, this is an indication that the wastegate is not closing completely.

If low boost pressure is observed, this is an indication that the wastegate is not opening completely.

Inspects the inside of the turbo outlet hose for standing oil

Inspects the impeller for damage and whether the impeller is making contact with the inner housing and checks to make sure that there are no loose bearings (if any of these conditions exist, it is an indication that the turbocharger is defective)

Checks the voltage and resistance of the turbocharger boost sensor electrical circuitry and connectors (if the voltage and resistance readings do not coincide with the specifications that have been predetermined by the manufacturer, the circuitry will need to be replaced or repaired, as necessary)

Common mistakes when diagnosing the P2261 code
One common mistake when diagnosing the P2261 trouble code is not inspecting the turbocharger oil system to determine whether it is necessary to clear debris and/or obstructions.

Another mistake that is commonly made is replacing the turbocharger before making sure the wastegate and circuitry is operating properly.

 

All of those clues do indeed mean you have the GMTU. And some ZZP extras.
If the MAP was replaced I wonder if it was replaced with the correct part for the GMTU? And is it banging into the AC compressor.
I'm pretty sure the code is causing the drivability problem; since clearing it made it run better. A lot of codes turn certain functions off.

My guess is the P2261 has something to do with the vacuum tank leaking.

 

If it was the lower TMAP sensor that was replaced, did the tab get trimmed off of the sensor? This would be if the correct upgraded 3-bar Bosch TMAP sensor was installed.

Perhaps a boost leak test would help diagnosis.

 

Thank you all so much for all the information. I got a lot to diagnose as i can tell with the first post and a little worried this may have been a mistake but I will hang in there if this community sticks in there with me. I really appreciate all of your help and expertise. I am also worried that maybe someone flashed the tune to factory and it needed the upgraded tune with the zzp stuff because they don't know what was altered before messing with it. Is there any way to tell if it was tuned? The map sensor I was thinking the same thing but tried giving the gm tech benefit of the doubt.. If it had the wrong sensor then it would last awhile without engine light correct? About 1k miles ? I got 84k on it now and it was replaced at 83k. Anyone have pictures of the new vs old tmap sensor. And what that shaving looks like.
can a bad tune cause turbo fluttered? When I let off gas it seems to flutter like bpv isn't working with my new forge none vented bpv.
can I test leaks for vacuum system easily?
I need to do a boost leak test.. I will try that asap..
If I reset battery and everything feels so good For a little bit does that give anyone anything I can check that may be easy?
Can I do a removal of any solenoids to see it picks up?
if it was a boost leak wouldn't it be bad even after a battery reset?
Thank you all! Will try to get under hood tonight and try to diagnose more. Just need a easy area to start.

 

The tune can be changed from stock to performance

 

If the vacuum tank is leaking the fuel trim could be affected. The vac tank operates the bypass valve. Thus my suspicion.

 

I had a similar journey chasing that code, tired new 3 bar sensors, vacuum tank, etc, etc ,, it was very sporatic, I wanted to upgrade the intercooler to eliminate the issue with the plastic side tanks, and low and behold the plastic factory clamp on the lower charge tube was loose like it had cracked or something. New charge pipes and new intercooler no more sporatic boost issue and no more codes..

 

I would agree with donbrew, first look for a vaccum leak associated with the bypass valve. This includes the lines, vaccum tank, bypass solenoid, bypass valve.

Also be sure that the P2261 is a current fault code. You say secondary, could be historic code. If it's historic, we should be concentrating on the current code P2178.

Yes, pictures may give us some information we don't have yet.

 

Symptoms of a P2178 engine code may include:
Malfunction Indicator Lamp (MIL) illuminated
Lack of power
Occasional misfire
Poor fuel economy
Potential causes for this code to set are:
Faulty air/fuel ratio sensor/oxygen sensor (AFR/O2)
Faulty mass airflow sensor (MAF)

Read more at: https://www.obd-codes.com/p2178
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I’m still thinking MAF is dirty, use MAF sensor safe to clean it.

https://www.chevyhhr.net/forums/hhr-...-sensor-54289/