P3000-123, strange behaviour of hybrid system

Hello people.
I have a 2004 Prius with about 210000 miles.
I had some roof cracks and a lot of water in the trunk. After I drained the trunk and fixed the cracks, check engine and all the other lights came and the code was P3000-123.

I removed the battery cover and the contacts were corroded:







I cleaned all the bolts/plates but I still get the code P3000. When the check engine is on, the MG1 turns the ICE at full speed to drain the battery.

The orange plug on the battery ECU had a lot of rust. I cleaned it.

Now, the block #7 goes up and down, when I regen it goes from 15V to 17V in one second, and then back to 15V when I discharge.










Any advice?

 

Thanks for your reply. I checked all the nuts and they are all properly torqued.
The fan connector is deleted and the connection is good.

I checked the voltage on all the cells and all of them are between 8.1V and 8.5V except for the 14th cell which measures 7.6V. I think that is the culprit.

Now I need to buy a used cell but how to measure it’s capacity?