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Discussion Starter · #1 ·
I had OnStar run a diagnostic:
HCP - Hybrid Control ProcessorP1F64The Engine and Transmission System is not performing as expected. An issue has been detected in the Hybrid Powertrain System that monitors and controls the use of power between the combustion engine and the electric drive system.
ECM - Engine SystemP0AC4The Electric Drive Unit is not performing as expected. An issue has been detected in the Motor Control System which monitors and controls the electric motors used to propel your vehicle.

After AAA left, I drove it around for 40 minutes, turned it off and restarted fine.
Engine warning light is lit.
Oddly, the headlight knob's on/off function, when twisting the knob to the left, is inoperable. I can turn the headlights on by twisting the knob to the right, but twisting to left doesn't turn it on/off.

Next step go to the dealer or does anyone have suggestions I can try on my own?

Thank you!
 

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Replace the 12V battery if you haven't done so already?
 
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Discussion Starter · #3 ·
One other thing: Though the electric battery is showing as fully charged on the dashboard (i.e. green to the max) the fuel range for electric is not lit up.
 

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Thanks; is that a fairly reliable first step?
Before firing a $200 round from the parts cannon, you might want to verify the battery is the problem. Suggest you check the power draw immediately after shutdown and then after 30 minutes; some devices don't shut down immediately after shutdown. If more than ~15mA, there is something staying on that shouldn't be. If no large parasitic draw, check voltage of the battery after sitting overnight without the EVSE plugged in. If battery still reads over ~12.2V, the battery is probably good.
 

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I'd go with the 12v battery as well. Your car is five years old and you're right about the midpoint for 12v automotive battery life expectancy (3-7 years in general). Couple this with the fact that the car's computers fired up when it was jumped points me to the 12v battery not holding a charge or providing sufficient current to start the computers.
 

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Discussion Starter · #9 · (Edited)
Before firing a $200 round from the parts cannon, you might want to verify the battery is the problem. Suggest you check the power draw immediately after shutdown and then after 30 minutes; some devices don't shut down immediately after shutdown. If more than ~15mA, there is something staying on that shouldn't be. If no large parasitic draw, check voltage of the battery after sitting overnight without the EVSE plugged in. If battery still reads over ~12.2V, the battery is probably good.
I jumped the gun and replaced the battery for $225 without reading your reply carefully. How do I check the power draw on the 12v?
 

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I jumped the gun and replaced the battery for $225 without reading your reply carefully. How do I check the power draw on the 12v?
The simple answer to your question is to place an ammeter between a single battery terminal and the cable (in series). However. at this point, the next step would probably be to check for small (millivolt) voltage drops across each of the fuses to see which of the circuits have current flow after the normal shutdown time. However, I'm guessing that you would be best served by taking it to somebody with a bit of automotive electronics experience to track down the faulty component.
 

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clamp on amp meters are cheap - and most A/C electrician amp meters have a DC setting.
 
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