This car is doing 'it' again. Posted earlier how it acted when trying to start.
This is a push button system, no key, fob only.
Pushing button results in lights on dash flashing, o/h courtesy lights also flash as do the front leds.
Radio powers on with no station - static only.
Relay (starting I am assuming) clicks several times.
I have an X700 reader but I cannot make sense of what it says- mostly because I can't start the car as it directs me to do.
There are faults on many systems.; I see low voltage faults to several systems - the battery voltage reads over 11 volts so I have an issue with these faults.
I have no way to start this car. Last time a similar thing happened it seemed to cure itself after a few days. Doesn't give me a good feeling for dependability.
I suspect the current sensor on the negative battery lead but have no way, to my knowledge, of verifying this.
Also suspect an issue due to cold weather within any one of several modules. Again, no way to verify which module is actually causing this as there are faults for several modules.
I don't know where the voltage (not current) sensor is, I do suspect that. I believe it is a part of one of the modules but not sure which one.
This is one of the most difficult faults I have attempted to fix, partially because I believe it is an intermittent probably due to excessive cold (been in the SD'* or below zero nights) and car is not garaged.
Does anyone know of any history of any of the modules used in this year of impala'* to be common areas of concern? Any ground pads that are common problems? Any connectors that have common issues?
It doesn't easily communicate with the X700 scanner. The scanner does read what the car is, VIN etc. But it is showing something like seven modules as faulty.

We are ready to trade this car, shame because the wife really likes how it handles and rides. Still, it has to be running before trading.

You should be able to get codes without starting the car. Do you know how to use a DVOM?

11 volts without cranking? Sounds like bad or discharged battery.

Wasn't it having signs of bad battery last time?

I vote new battery. A good one, too.

A battery load test is definitely a good place to start. A fully charged battery is 12.6 volts. If the battery is 4 years old or older then you probably need a new battery. Start there!!!

Thank you all for your input.
The 11.1 volts was measured after multiple attempts to start the car - none of which resulted in any motor cranking.
The codes at that time were all over the place, multiple modules.
This happened a few months ago, similar situation. The wife started the car remotely - it time out and it wouldn't even crank when she got in and tried the pushbutton.
Same thing this time, weather outside cold, very cold which isn't a friend to battery life or voltage.

I put a smart charger on it last night. The voltage today was 12.6, totally expected with the overnite charge.
And of course the car started right up, now today the temp was in the 30s.
It still had codes on it: The most meaning to me is C-0800 which is low voltage sensed.

The dash has the icon for the immobilizer lighted. Car goes into gears and drives. Also remote start works and car starts after inside started from inside. Immobilizer icon still lighted.
Unsure why this is lighted. All buttons on remote work.

I will have the battery checked as this appears to be the probable culprit. Could be the battery was getting weak and the cold finished it off.
I will add an update after the battery load test.

Thanks again to all.

How old is the battery?

Age of the battery unknown! Probably at least three years old.
The recent cold snap did not affect the car at all.
I do suspect the battery as the most likely cause of this. Still I don't want to change it in a 'shotgun' approach ( where one just starts changing parts ).

It could be a temperature sensitive component in one of the PCBs, sensors or even a microscopic crack in a cable/connector.

For now, all is well and spring is coming. I expect to have more issues with this car on this. Load testing did not show any problem, also showed alternator as ok.

That'* good news!

If you don't know the age and/or quality of the battery, and suspect it is over 3 years, I'd replace it. Does it have a manufacturer and/or build date on it?

What did it have for CCA?