I hope you realize that disconnecting the battery cables while replacing your battery, will clear the codes stored in the computer.
That's the poor-mans reboot or as some around here call it, a battery "lobotomy".

 

So, what’s the next step? I had no idea. My other vehicle is a 2005 GMC Canyon with 300,000 miles. The maintenance was easier. Do I wait for the codes to reappear?

 

There isn't a next step. The codes should not reappear. It sound's like you fixed it.

The Canyon maintenance wasn't easier, you just never had problems. It would have done the same thing with a bad battery. I'd bet there's a few Canyon owners out there with bad batteries that experienced most of the same issues you had with your HHR. I had the same issue a couple of years ago with my GMC Sierra. My battery was at 12.3 volts. It wrecked all kinds of havoc, what made it worse was that it was -5 outside at the time.

 

Drive it...

 

At next break in the weather I'm going to spray my seats with staticguard. Why? I get shocks from my 2008LE even in humid weather. I think MAYBE it's just static from the upholstery, but the radio used to "snap" randomly when I drove, and I thought that could be related. I have since replaced all audio including speaker w/ aftermarket speakers and vintage GPS/radio, plus retrofitted an OEM subwoofer. No more "clicks" but the unit crashes periodically, and I still get shocks. I'm leaning toward upholstery cause both shock and radio problems. Hope so because I dunno what else would cause it.

 

https://www.wikihow.com/Get-out-of-a...ic-Electricity

 

What is The Canyon maintenance ?
Is that slang for changing the battery ?
Thanks

 

Update, the display has shown the 'low tire pressure' light. I will wait later until I do the scanner to check the codes. I'll look into spraying the seats with static spray as well. Thanks

 

Post #43 (his other vehicle)