Hybrid Battery Diagnosis and Differences Prius Plug-in Vs Prius

Hi! I have a 2012 Prius Plug-in with 270,000 miles.

A few days after replacing my head gasket, I received the code p0aa6 and a message on my dashboard stating, "Check Hybrid Battery System Stop vehicle in a safe place." The car still goes into ready mode and is still driveable.

I've already checked the 12v battery, AC, and inverter and found in the Dr. Prius App that the Delta SOC number is often in the red.

Knowing that the problem likely lies in the hybrid battery, I wanted to know if there was an easy way to tell which of the four battery modules needed to be checked. I wasn't entirely sure what to look for or what all the graphs meant on the battery monitor portion of the Dr. Prius app.

I did perform a life expectancy check on the car on Dr. Prius, but all it told me was that my battery had an 80% life expectancy. I also tried recording my data on the app, but it gave me a lengthy document of data I had no idea how to interpret.

Another question I had was, once I'm into one of these battery modules, are the isolation/insulation tests the same between the Prius plug-in and standard Prius? I know that on the regular Prius, they're split into 14 different segments with two cells per module, but on the plug-in, it says eight on the Dr Prius app. When looking at the Hybrid battery, I see that each module is numbered on the four modules on the Plug-in, but they reset halfway through and say "1 2 3 4".

Overall, I'm seeking guidance on how to fix the P0aa6 issue. Will I have to check every single cell, or is there a way I can only check one of the four modules?

Attached are a couple of pictures of using the Dr Prius app.

 

I’ve used the car for about half a year now and have driven about 7,000 miles in it. I think I may have been using the wrong terminology in my question as well. I have the case opened up in the battery and can see the individual smaller batteries amounting to 56 as you say, but they’re in four separate containers and I was wondering if there was a way I could be able to quickly see which of those four packs had the bad 3.7v cells, so that I wouldn’t have to take apart all of them.

The number 8 came from the 8 bars in the dr Prius app and I was just trying to make sense of why was there 8 instead of many more and saw that those packs on the battery were numbered 1, 2, 3, 4 then repeats halfway through saying 1, 2, 3, 4. I assumed that had some relation.

I appreciate the lead though! I’ll take a look into the resources and tips you’ve provided me!