Help With HV Traction Battery - Voltage(s)

I'm back to tie up loose ends, and help anyone else that may run across this issue. I did manage to manually charge the battery cells (don't do what it did because it's dangerous, but I used a 12v 2A charger and linked batteries into 'cell packs' of 3, one at a time, and brought them up under supervision like that -- yes, all of them). So, they were all reading pretty damn close to what they should, and I got them within .2v of each other as well!

However, the car still refused to start. It still said "Check hybrid system" and wouldn't go Ready. I had a plethora of codes, that I was fairly sure was the issue. Codes for the HV circuit relay being intermittent, codes for the plug-in portion not functioning at all, all sorts of (seemingly) random codes. However, after many many many frustrating hours of trying, I found a very curious thing in AllData, advising about a feature that sounded a lot like "ignore the fact that the battery pack is low, and try to start anyways" (I forget the exact option). It is in Techstream (I used 12.10.019) under Hybrid System/HV System, then 'Utility'. It will basically ignore that the voltages are low, and allow you to start the vehicle to Ready / On. It eliminated that "Check hybrid system" message on the dash, for me, and allowed me to start it (but not without warning that if you turn this safety off, and don't have your issues fixed, you might set yourself or your car on fire -- so be careful!) When this is done, you can give the vehicle gas while in P and charge the HV battery, to what it wants to see.

And that, is how I tore my hair out for hours and hours, over a damaged ECU (I replaced it with a used one), and a battery that was too low for the Prius to want to start. Surprisingly, I never came across that tip anywhere, to try it. I hope this helps someone in the future. Thank you all again for all your help and suggestions!

 

Just came back to update for anyone else who may run across this thread in the future. The exact name is "HV Batt Cell Low Volt READY ON Prevention Cancel", under Hybrid System/HV System > Utility. Here is a PDF of some info related to this that I snagged from AllData, since I know many of you might not have access to it. I hope it helps someone!

 

Yes sir, I tried clearing the codes, everything -- and even after I swapped the main ECU (in the engine bay next to the fuse box) it still had the "check hybrid system" message. The only thing that allowed me to start the vehicle with that message was using the methodology I mentioned (the ready on prevention cancel option), after running that it started just fine.

On a separate note, I also realized that the 'low voltage cell stack' codes are permanent codes -- even after recharging the vehicle by running it and clearing things with Techstream it did not seem to get rid of them. Take note of whether they are X'd as "Permanent" or "Permanent" AND "Current". The only way to get rid of "Permanent" but not "Current" codes is to prove to the vehicle that the condition is fixed (and sadly most of the conditions, even in AllData, are listed as "Toyota Intellectual Property"). Even reflashing the ECU doesn't seem to get rid of it.

 

Yep, everything's good to go here. I just came back to update this post for anyone else that might stumble across it when trying to fix their problem.