Project 166k miles w battery code, order of approach?

This is my first post, although I have been reading the posts for a few months. I am trying to remember all the threads. I did buy a factory service manual, the car was inspected by a non dealer shop, and I test drove it for a couple of hours. They did a scan, but I would like to buy a scan tool that will work in addition to Techstream, which I also plan to try. I am trying to just get it running, and will try to go for a 2015-2016 wreck used battery.
The car has been parked for 2 months, and I started it for a few minutes. The battery fan went on (on high it seemed?). Here is my plan prior to locating a wreck gen 3 battery:

1) Inspect trans fluid for clear, and change if dark red (engine oil looks new). Check all other fluids.

2) Try to read any stored code info with the scan reader you might suggest (other than Techstream)

3) Disconnect 12 v battery, then Red HV battery plug (using one hand, DMM, HV gloves, etc.)

4) Remove HV battery, and both bus bars, measure voltages, and do a brief load test on the modules with only current state of charge (probably one minutes at 45 watts head light bulb load). I will try to determine if another cause is present for the code other than the modules.

5) Replace up to 4 modules, balance pack for 24 hrs. Thinking to skip module cycle conditioning, and resistance matching.

6) I plan to find wrecker gen 3 modules if car goes for a few days without a lot of problems. The cost of the RC chargers would go to the gen 3 battery purchase (28 modules).

I am a retired Technoid, and this Prius (2005) can take the slow project path since I have a bunch of other wheels I keep running.
The motive to buy was simply to keep learning about Toyota products after owning 6 Corollas.

Thanks to everyone for helping to keep such a great forum going, and for all your suggestions.

 

Ran car for 2 hours, used Torque Pro with a Gemwon WiFi scanner, and a BAFX OBDII blue tooth scanner. Was able to get: P0A80 (voltage between modules too great), P3018 & P3017(not in my factory service manual?), and P0420 (catalyst system and possible other systems). The 12v battery (monitored under hood) started at 11.2 (no smart key), 14.4 upon starting,and immediately after shut down, 2 hours later, was 14.1 volts.
The charging bars went to green all bars after about an hour, the ICE never turning off. The charging path arrows would go on at 1200 rpm, and off at around 1k rpm in a cycle of about 1or 2 minutes.

The engine is very smooth, and the overall appearance of the car is very nice, seemingly well cared for.

Besides the modules needing attention, might I need catalyst, or cat sensor, or related trouble shooting? Dealer mentioned that after the battery condition is fixed, often the other codes go away... but I am wondering now. The other non dealer shop mentioned a code for solar sensor, or perhaps it was the P3018, P3017 (which Torque Pro labled Powertrain pending?). All codes were in a yellow (pending?) color except the P3018.

I will move the car to a better spot once the snow melts, and then open the HV battery. I thought Torque Pro would show HV battery block voltages????

Thanks for reading, and any thoughts.

 

I was able to search out many of my above questions, and will try Hybrid Assistant, and Hybrid Report tomorrow.

 

Thanks TMR. I will try to get some DMM reading on the sensors you mentioned, and put some PB Blaster on the CAT sensors.

 

Ran Torque with the Gen II battery PIDs. I added all blocks to display HV block voltages, and here are the values shortly after power off:
Block 1) to Block 5 )16.7
Block 6) 16.6 Block 7) 17.1
Block 8) to Block 11) 16.6
Block 12) 16.7
Block 13) and Block 14) 16.6

Delta SOC is 1.1 %
It's funny when I test drove the car 7 weeks ago, it sat or rolled a bit under battery power before the ICE started. Now it seems, the ICE always starts even when showing full green bars to the top? Is my battery control ECU perhaps going out? The car at this time is stuck in snow. The 12 v battery was low from sitting in the snow for 7 weeks, but is climbing slowly to 12.4 volts (target 13 + volts) by these scanning runs. Will be able to 110 AC charger the 12 v battery once the snow melts (at 2 amps, of course).

Now what is really funny is that I also found HVB Min # (Num) reading at about 6 volts right after the ICE started (ICE now always starts seconds after Power on). After a few minutes running, this PID was varying its voltage erratically and rapidly all over a range of about 1 to 16 volts, and then settled only after Power off at 13.0 volts. All the bars are green and at the top, HV (SOC%) was always showing 100% throughout the entire run. The blower motor seems to always be on high no matter even if battery temps are like 60 degree F?

Block 7) did drop to 13 volts when I went into drive (part throttle) with the brakes on for perhaps 30 seconds.

I am so hoping to find only a corroded or loose bus bar, but will not know until the snow melts away and I take it all apart.

 

I need to move it closer to 110 AC and out of the way of coming projects. Once it is in a better spot to perhaps sit for a few months, I will take chances to disable it. I read in the posts that a fully charged 12v is needed to avoid weird stuff, and I do think some weird stuff is happening even though I am a total newbie to Prius. Once 12v is fully up, I might get a chance to hook up Techstream, the catalyst system voltages can be checked, and a look for whatever OBDII data might still be being maintained by the 12v before I disconnect the 12v.

This is so utterly complex a car that it is fun! I can not believe there is no PID for oil pressure, but I get to know 0-60 times, the angle of lean of the car, and its altitude (lol). My avitar pup is showing his take on the priorities of data acquisition.

 

Today, 8 days since I last idled the car for an hour to charge things after a snow burial of about 10 weeks, I came back to it to find it completely dead with only 3 volts showing on the 12 v battery. I used a jump pack to start it, and the Christmas tree lights were gone (Torq was showing the pending codes of P0A80 and P0240) as I started to check voltages by using Torq. Most of the blocks were showing in the 17-18 volts except for the block 7 at around 13-14 volts. The MFD was showing one purple bar at start, and in about 10 minutes I had the green bars to the top, and the engine did turn off at that point. The battery cooling fan was off or at 1, and it seemed to start to behave as I believe a normal Prius would. After the engine stopped, I disconnected the jump pack alligator clips, closed the hood, and started to drive to the planned work spot some 100 feet away (up a small hill). The engine restarted after about 30 feet, and I drove to the out of the way work spot (110 volts ac here). Once stopped, the engine cycled on and off in a cycle of about 10 seconds and on about cycle 10, the Christmas lights came on again. It is now parked with the 2 amp charger on the 12 v battery, and I will likely start to disassemble the HV battery tomorrow. I noticed the engine coolant tank was showing NO coolant, so I will buy some to add as a 50/50 distilled water mix before I run the engine again.