Hybrid batteries vs Hybrid ECU?

I've learned a LOT from this forum, thank you!
Now, i need to learn another thing... LOL
How can you tell when the ECU is going bad, and not the battery cells?

I should have replaced the whole pack when this first happened, but i replaced a single cell instead, and have been since then... Maybe 6-7 cells replaced in the last few years. I replaced another bad cell over the weekend, and cleaned the fan, it was DIRTY! Blew out the rubber lines, and wipe the black plastic tubing. I put it back together and all seemed to do well. Until i went out to the car at lunch today, to make some phone calls. I had the side doors open, but it got HOT with no wind the and the sun on my. So i turned on the car/AC. All was well. Then the dash lit up after 10 min, again with the red triangle, check engine light and (!). So i used the bluetooth scanner with the torque app and it showed P0A80 again. No back cells. The batter temps were about 102° (fan lvl 2), so i assume that is why the code came up? I'll scan it with my laptop when i get home from work, but i suspect it might show P3000, without indicating any bad cells, just those two codes... Over the weekend before i changed the bad cell, it threw P3000, P0A80, P3017, P3018 (after testing the two cells are fine), B1411 & B1421 (pertain to the AC, but it works fine and been on forever), and this one i think is new, C2318 "Low voltage error (power supply malfuntion) under the transmission tab in techstream. But i think C2318 might have to do with the other codes and bad cell (14.3v).

On Friday, i called the dealership (while still in traffic) and they said that they had no way of being able to tell if it is for sure the ECU or not... Just as i got stuck in traffic and the bad cell kept throwing a code, not matter how many times i cleared the codes. Then, i was stuck in traffic. It got so bad that i could feel something disengage and it no longer charged the HV batteries. I couldn't accelerate over 16mph! I was stuck going up a small hill, and traffic was passing me. Once i got momentum, they stopped again. Once i got to my destination, i turned off the car, waited a few minutes and turned it back on again. It started charging the HV batteries again, thank goodness!! So i was able to get most of the way home without the code showing again, and definitely no acceleration issues.

The car is a 2006 Prius with over 220k miles, i'd like to get past this Michigan summer and at least until spring, before i replace it. I think the cool weather will help, a lot. I just use it for work, not long trips across the state anymore, not reliable... This previous fall/winter, it would rev really high once all of the charge bars were green. It seemed to shift a little funny, but i think that was because of the cold. I started driving it last fall when my wife started driving our new 2012 ford flex. My wife did say it started shifting a little weird when she accelerated fast, that after i changed the transmission fluid. I drive it like an old man and haven't noticed that... lol Sometimes it shifts a little hard when going slow and switching between battery/gas. Not horrible, but noticeable... Not sure why????? Slightly low on fluid? Hard to check these things...

Summary: Is the ECU bad? Just replace the whole HV pack? Could the transaxle be going, too? Deal with the heat and keep clearing the codes, and see if it keeps happening this fall?

 

I don't know... I replaced the engine/belt driven water pump, i think last year. I'm not sure about the inverter... I feel dumb asking, but how can i tell if coolant is moving? I just googled "prius electric pump inverter" and it looks like it mounts to the inverter. I've never touched it and actually just learned the name of that unit, just now.... LOL I did replace the spark plugs slightly over a month ago, doubt that has anything to do with anything, but i've seen other threads ask about them being replaced for some reason....

Edit: I just read more about the inverter pump. I didn't know that it as linked to the transaxle fluid, i thought it was separate, just for the inverter. I bled it properly, but maybe it is a little low or some air bubbles left in it still? When i changed the transaxle/transmission fluid, i put the car on four jacks to get it off the ground and to make sure it was level. Just as fluid was coming out the fill hole, i capped it. Is there a way to check the fluid level, besides jacking it up, making sure it is level, then opening that bolt/cap?

 

Thank you VERY much for your response! Yes, definitely been playing whack-a-mole... While i've learned to test the batteries using my multi-tester and a vehicle headlight, i still feel like i'm missing something. From all of the posts that i've read, it feels like information overload and a bit overwhelming...

1. No corrosion. All is good. I took my time putting the battery pack back in and visually inspecting everything. I took a pic of the techstream screen, everything looked normal last night, minus the cell temps.

2. On some battery packs, if one was obviously low at 12v or 14v, i had only replaced one. But recently, i couldn't tell which was bad in the group, so i replaced both, the last few times. The last time, i only replaced one. It usually worked for 6 months, before another dash light came on with a cell group that went bad. This summer, all the time now.....

3. i have tech stream and torque pro. i use torque to clear the codes, when i assume it is just hot cells... then use tech stream when i get home to see if any cells went bad.

Last night, i scanned again, these are the pics. These are the only two codes that came up. In the active test, i only see the battery pack temperatures as high, everything else looked normal. Am i missing something?

 

Thanks, i was confused from the posts that i read. Each have separate coolants, but the inverter pump circulates both? I've replaced a jeep transmission, but this transaxle, i don't fully understand yet...
I checked the oil and inverter coolant levels before i left work yesterday. They showed showed normal. Also, there were "waves" in the inverter coolant reservoir. All appears normal.

 

Thank you very much for you very in depth explanation! I change the oil myself, using Napa Full Synthetic and a Platinum filter. I replaced the water pump about a year ago, maybe less. And just over a year ago, i replaced the transaxle fluid, using the expensive proper stuff and watching a good youtube video. I have not replace the inverter pump, but i still see waves in the inverter coolant reservoir. But i did not understand how everything worked within the system.... Good to know though, thanks again!!!

The screenshots were from when i was driving, should i test it again while stopped? I was going about 55-65mph...... By doing this test, will it balance the batteries? Or better show what cells are bad? Both? When i put the car in reverse, how far do i need to drive? Or keep my foot on the brake? Thank you for your in depth response!

When i most recently replaced a cell, i very thoroughly cleaned the fan, which was really dirty. Then cleaned the black plastic tubing, and blew air through the rubber hose the connects to the top of the batteries.

 

Thank you for your quick response! What if none of the cells are "bad"? Is there another possible reason why the batteries are running hot, other than it is really hot out, and they are getting older?

 

Makes sense, thank you! I'll try to test it tonight.

Last night, i drove more than just to/from work, which usually signals a dash light, as the last little bit of driving is in town, so i uses the batteries more... Plus the cells have been heating up. But it did show P3014 (Battery Block 4 Becomes Weak). So i'll have to take it apart again this weekend.

I did not use a torque wrench, just kinda guessed. They aren't loose, but i'm not breaking the treading off, again........

I did not know what the snowflake was for, thank you! I'll post those for sure, hopefully tomorrow! Working on this almost every or ever other weekend is getting old. Definitely wish i did it the correct way, the first time, and learned the correct way of doing this, since then. I had gotten lucky, because it would last usually 6-8 months, before another cell would go bad. Now it is all the time.....

 

And it is MUCH appreciated!!! As my wife and I work through the Dave Ramsey plan, we have everything paid off but the house and a 2012 Ford Flex. Once the flex is paid off, i can start saving for another car, probably a newer prius. But with my second child on the way(JUST found out) and still have an entire floor to finish in our project house (looked easy after watching HGTV), the more time i can work on the house and less playing whack-a-mole with prius batteries, the happier my wife will be!! LOL Thank you all for your input!!!

I'm decent with maintenance and before the ford flex, all vehicles were around 220k miles, or more! The '95 wrangler only at 156k. lol But with any other project, i find the issue, replace it, and back on the road. I'm having trouble wrapping my head around what all is involved with the prius, as it takes a little more know how. I'm very thankful for all of the input! I played hookey and took the jeep to the sand dunes yesterday, so i'll for sure test the prius tonight/weekend.

 

These 4 images are from the charge mode, just over 2 minutes and full green bars. HV control and hybrid battery tabs. I was rushing and accidentally unhooked the 12v battery, while taking stuff out. Amd remembered i needed to do this test still. But it reset the codes. So these codes are before the code came back on. But since it is the charge test, safe to assume it is ok?