My gf got a 2008 hhr 2.2 lt it has just under 150k ran great, we met at school so during the summer her and I live 4 hours apart. on her way home from visiting the check engine light came on and had a po171 and p2270 and p2271 codes which leads me to believe it is the o2 sensor. it struggles to start but when it does it runs just like normal, it happened out of no where. does anyone have experience with this same issue?

 

Welcome to the site, yes but it was a dirty MAF sensor. It could be the start of the flex pipe failing also, per

https://www.obd-codes.com/p0171

 

That is odd! The O2 sensor is stuck lean AND rich.

I would look for wires going to the #2 O2 sensor laying on the exhaust pipe. Could be the the #2 O2 sensor is bad. #2 is the one after the cat, under the car.

Also look for vacuum leaks around the manifold and check the EVAP purge valve.

 

P2270, yes exhaust leak in system prior to the O2 system, hmm flex pipe? Flange gasket?
Or burnt wire harness

https://www.obd-codes.com/p2270

P2271, second verse same as the first, exhaust leak prior to O2 sensor, or burnt wire harness

https://www.autocodes.com/p2271.html