I just had the same issue. Mine would flash the Problem with Aux Battery message randomly. I checked the aux battery and it was sitting at 12V and charging at 13.8 but the voltage would not get above 12.0V. The dealer wanted $300 to replace it. I found a replacement on amazon for $45. It took longer to get the covers off than to replace the battery. I have not had any messages since. It was the original battery so it was six years old.

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Dave
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