GEN 2 P0A09-591 the ol' red triangle

First off ~ I'm no mechanic with years of experience! I just started doing my own brakes last year....

I'm a network/computer/phone guy ~ somewhat handy with tools. NOT A GENIUS

Long story ~ my 2014 Prius V with 200K had the morning rattles that turned into blown head gasket after I did all the EGR/intake manifold cleaning. Had a mechanic do the head gasket and water pump with the head milled/decked whatever the correct term is.... $2,000 and had my baby back after driving my 06 4runner around for 2 months spending $400 a week on gas.....whine/piss/moan ~ anyway, got her back on the road and back to 43mpg VS 15mpg of the 4runner. She felt like she was running great, day two of driving blew a hole in the crank case.

While on the hunt for a gen 4 1.8L to swap into my gen 3 prius V I picked up a 2005 with 179k one owner no rust gen 2 with a bad HV battery for $3,000.

I swapped the modules out of my gen 3 into my gen 2 and she still showed the red triangle and showed a P0A09-591 & P0A08-264 with techstream. I've read through the other posts on P0A09-591 and will ordered a repair manual if I can't find one cheap or free online. (I'm a CHEAP bugger)

Thus far my findings and repairs. the previous owner an 89 year old guy purchased a new 12v
Diehard AGM S46B24R 06/2021

it appears to have the usual water leak that corroded the connection in the pic above the 12v batt ~ see repair, even though the yellow & purple wires weren't corroded if I touched/moved the connector I could hear some electrical component click on/off. so I eliminated that failure point as well. I would like to know if anyone knows what these wire function are??

Also, opened the fuse panel under the hood and found the corrosion failure of the blue wire pin 4 on this connection at the top of the fuse box. Does anyone know what this wire goes to?

** the cruise control doesn't work or light up when I push the button(no codes on techstream) & I have an 02 sensor code that I'll work on after the HV codes are cleared.

The car runs great with my gen 3 modules & I'm getting 44mpg in-spite of having the codes

*** the p3000 code is gone ~ the only remaining codes are P0A09-591 & P0A08-264 & 02 sensor

I put some red liquid electrical tape at the top of the shrink melt butt connectors for peace of mind of water running down.

I don't know how I should fix that corroded off blue wire issue in the fuse panel under the hood??? ~ I'm guessing that that is the cause of my low voltage DC problem?

I don't ever hear the HV battery fan come on or blow, would that throw a code? I did clean it ~ was caked with crud. I did spin it fast with air compressor while cleaning and I think someone warned about that??
Any insight or thoughts or criticisms of my disorganized explanation are welcome....