I have an 08 with an LNF with 80K (the original engine was porous.) I had the intake and exhaust camshaft position actuator solenoid valves replaced, and those codes disappeared. I now get P2090. Any suggestions?
I have low boost pressure, about 6# also.

 

https://www.obd-codes.com/p2090

 

Certain trouble codes will limit the boost to about 5 lbs. Fix the problem and/or clear the code and full boost should return.

 

It means that the exhaust CMP control signal is shorted to ground.
The OBD-CODES guy doesn't know what he is talking about. Another parts changer.

 

What codes disappeared? (The actual numbers.)

What parts were used for replacement? Cheapie generics or OEM/AC Delco?

P2090 Exhaust Camshaft Position (CMP) Actuator Solenoid Control Circuit Low Voltage

Possible defective exhaust solenoid or bad connector or wiring.

 

I do think it’s a worn or stretched timing chain.

 

Evidently the shop manual is just wrong.
It says :
If the circuit was open it would be P0013
If it was a bad signal it would be P0014
If it was the chain it would be P0017
P2090 is the cam position CONTROL circuit shorted to ground. It is a 2.0L only code
Here is a pdf of the article, you can look for yourself via the FREE service manuals link in my sig.
P2090.pdf

 

Very interesting!

 

That's what the code means for an HHR SS. But the OBD-CODES.COM article was written to help diagnose many makes and models. The first steps are pretty much what your PDF advises. Check for TSBs, check engine oil level and condition, check wiring. After that the steps are vehicle specific and require advanced testing equipment and procedures.

 

First line for common causes, worn timing chain