Hello all. I am nowhere near a mechanic but I've done a few repairs following information I've found online. As stated in the title, my car is a 2015 Impala LT. This morning my check engine light was on when I started my car. My cheap OBD tool tells me it's error code P305F, Engine Control Module has set a performance issue with the Dual Battery Control Module. What I've found online is that the vast majority of times this is a bad auxiliary battery. I could pick one up from AutoZone right now, but before indeterminately dropping $150 I figured it would be worthwhile to do a little testing. I checked the connections on the main battery, DBCM, and aux battery and everything is tight with no corrosion. Using a multi meter and info I found on YouTube, I tested the main battery and got a reading of 12.63v. I also tested the DBCM and read 12.63v. At this point I expected to find low voltage on the aux battery but when I tested it I read 12.8v. I'm not sure what more to check at this point. The car seems to be running fine other than the check engine light. Where do I go from here?

 

Based on some other advice I tested both batteries with the terminals completely disconnected. The main battery measures 12.48v and the aux battery measures 12.63v.

I also did some simple continuity testing on the fuses on the fuse assembly connected to the DBCM and everything was normal. I also removed the DBCM to try and inspect it. I found a picture online of what a burnt out DBCM supposedly looks like but without a good one to compare it was difficult for me to figure out what about it looked bad. Still I figured it couldn't hurt to take a look at mine. Does this look like it's in good shape?