As I said, clear the code and see if it come back. A HV isolation fault can CAUSE a no charge 12 volt problem. SO replacing the 12 volt battery will not solve it if there is a HV isolation problem.
If you clear the code and charge the 12 volt, and the POAA6 code come back right away, you know you have a problem. When it is linked to a start interlock code, it is more likely to be an honest HV isolation problem.
When the HV battery is making contact with the chassie, and the 12 volt battery is grounded on the neg side to the chassie, you have a situation where the DC-dc converter can't work (or at least not properly) and can cause either a draw or at best not recharge the 12 volt.
Trying to solve problems by throwing parts at it, isn't productive, Even if the codes are caused by a failing 12 volt, you should re-charge the 12 volt and look for DC-DC charging and trouble codes before "just replacing the 12 volt battery" because you don't understand the problem and it "might fix it"
I worked on heavy diesel trucks for years, and every engine that had a coolant leak into oil sump, the owner said it needed a oil cooler, and almost never did. oil pressure exceed coolant pressure when the engine was running so oil would leak into coolant if that was the cause, only leaking coolant back when the engine was shut down hot. Most often it was liner issues requiring a full teardown and re machining or liner replacement. I mention this, because people wish for the problem to be simple and waste money on "hope" rather than proper diagnoses. I also saw countless battery changes for bad charging systems and charging system replacement for bad wiring and/or batteries.
Any vehicle I have with trouble code, I clear and see if they return, and note the conditions under which that happens.
Continuing to push 'bromides" as the only cause, can make people throw good money after bad, that they could put toward the repair if they instead diagnosed properly.
This case is one that proves my point, it was a HV isolation problem all along.
I have 3 vehicle that use the small group 51 battery, One is a diesel tractor and has the oldest battery, I don't know its age because it came (used) with it when I bought it 5 years ago, the other is at least 4 years old and starts a Saab, these batteries shouldn't need replacement every few years. I don't know the age of the one in my Leaf, but it "started" the car in -20F temps.
I am not saying that a low battery can't throw a strange code, but a low battery is already something that should be diagnosed before replacing the battery, then once the problem is proved to be a battery that can't hold a charge (by recharging fully, then testing, only then replace and clear codes, re check the DC-DC charging system, and see in a few day if codes resurface.
