This is the problem. Voltage sensitivity. And, it has gotten a lot worse in the years since. When some module decides the voltage is too low, it can throw a code, or just act unpredictably. That threshold is a lot higher than you might think, too. Years ago, you just needed enough to get it started. Now all the modules need to be happy.

New cars today throw codes saying Module A can't communicate with Module B, and there becomes a pile of codes, and it can be hard to sort out. For example, if the BCM decides voltage is too low, it faults. Then the ABS module says it can't communicate with the BCM. Once the ABS is faulted, your backup camera is faulted and your parking assist, etc... So, the first thing to do is get the vehicle on stable voltage, and then see how many of these are still active. The faults come easier now in an attempt to keep the modules from getting flaky.

 

Yep, sometimes I miss the simpler times.

 

Broke down and bought a new battery for my daughter's '07 HHR. It still had the original battery in it. We're at 95k miles and I just found out she's been sticking cheap 87 octane gas in it. I told her if she doesn't want to spring for the premium then get the 89 because the last owner used 89 for the first 94k miles. She's got the 2.4L engine.

 

Seems the OE batteries really last a long time. I feel it is because it's away from engine heat. Mine was 11 year old & still testing good. I was leary heading into winter so I got a new one.

I have the 2.4L also, & have run 87 in it, the computer will de-tune the engine. but mine seems happiest running 89 at least, & I only run 100% gas.