Previously posted this in the wrong place, your CEL sounds a lot like mine:
2012 with about 38K on odo. I've had some cold temp issues with the ICE not starting. started happening 2-3 weeks ago when temps were 24 degrees and I got a warning message on DIC that the battery was cold and needed to be plugged in. Message appeared 2x during my 3 mile drive home. when home I popped hood and ICE ran. Put car in garage, closed hood, it was still running. I shut it off and restarted and no ICE. Next day temps between 12 and 14, no ICE. again, popped hood and ICE ran, switched to watch Power Flow on dash and saw no power from ICE to battery. Next coupe days seemingly no issue as it had warmed some outside. Week going in to Christmas with temps down, no ERDTT happening but did get the check engine (engine icon on DIC). Called dealer and made an appointment and by the time I got it in the light had cycled off, dealer called me and advised that 4-5 modules needed software update, out of warranty so I gave ok, cost was about $360. When I picked it up the service writer had called GM technical and had been advised based on stored codes that updates were needed and SHOULD solve the issues. I did notice that Mountain mode (I was using it to be sure that I was getting any charge from ICE so I didn't get stranded altogether) didn't seem to start ICE until there was 10 miles of battery left, previously when ever I put it in Mountain, the ICE would start.
Had check engine light come on again and due to timing and needing to use car I cycled through it again but took it out to have them do and OBD on it and it showed stored codes from prior. I told the writer when the light came on again I'd come right there so they could scan it. Well, that happened last Friday Dec 29th. Five years and one day from purchase. I don't remember what the code was but was told they'd need the car, I deferred appointment until today because I didn't want to tie the car up all weekend, just in case.
Light was still lighting this morning prior to dropping vehicle off.
Dealer called me at about 3PM this afternoon to update me that tech had called GM Technical again and technical has authorized/advised replacing the hybrid battery. He felt that "SHOULD" solve the problem. Fortunately it's warranty. battery due at dealer tomorrow, I may have vehicle back tomorrow night.
I will follow up with result. I am hoping that this does solve it, while it is a great car, it may be time to move on. I gave up an HHR for the Volt and have missed the room ever since.
I got the car back today, the advisor had given me wrong info about what was replaced. They replaced the Drive Motor Battery Charger. On the way back to my office the ICE ran almost the whole way (watching the "power flow" animation on dash showed ICE running but not charging battery), last 3 blocks it switched to battery power and almost immediately I got the warning "battery too cold, plug in to warm". That was the third time since Thanksgiving this year (never before since 2012) I had seen that.
I am confused as I thought when the ICE ran it ran to charge the battery and the vehicle always ran off battery, now the power flow shows the ICE powering the vehicle and when backing off accelerator it shows regen.