My 2006 HHR with 2.4 L engine has exhibited codes (mid-week) P0114 then two days ago P0174. CE light went off by itself both times 24 hours later. What do these codes tell you ?
regards,
Hewbie

 

Welcome to the site

P0114. Is related to the MAF sensor

https://www.obd-codes.com/p0114

P0174 relates to the first O2 sensor

https://www.obd-codes.com/p0174

Things to check.....
Is the MAF sensor connection tight , check the wires plugged in just up under the air filter housing




That's the wire harness, the picture shows the elbow disconnected but that's not necessarily a requirement to check the harness

 

I doubt it is really P0174. The HHR does not have a bank 2.
P0171, maybe?

They both would indicate the MAF is reacting to something, either a bad MAF or more likely a broken wire.

 

I'm betting, dirty MAF or ops I forgot to reconnect the connection properly.