HV Battery Voltage not even moving to different cells.

Ok, I have a 2008 Prius. I had all the fun lights come on. Pulled the codes (Don't have them written down) but the original code was a bad temperature sensor on the HV battery after taking it to dealer and getting ripped off for 400$ to be told that it was a bad temp sensor and the only recourse was to replace the battery I brought it home and took it apart.

I found that one of the wires going to the third temp sensor was broken and that several others were frayed. I used some high temp shielded butt connectors and fixed the issue. Put the car back together and it ran for 2-3 days. Lights return and I have a code stating that cell 7 is lower than the others, I assumed maybe the contact bolt had come loose so I went back in and tightened it up. (wasn't aware of torque spec at the time they are all over torqued.) It ran for another week or so and then I got the same warning for battery cell 10, again re-tightened but this did not correct the issue lights came back after about 20 minutes of driving.

Monitoring the battery while the car is running the cell it is saying low is often the high cell. It seems more like the cell is slower to respond to voltage changes than the others. Do I have a bad a cell or is it possible I'm just overlooking something?

 

Ok, I visibly inspected the wires without totally removing the harness and see no damage. It looks like one wire is showing a tiny bit of bare wire at the ecu connector. With the vehicle running I attempted to wiggle the wires up and down the length of the harness to generate a either a code or just to see a jump or drop in voltage. This never happened including poking and slightly tugging on the ecu plug for the wires. I tried this with the battery charging and with the battery under load and saw no issues. The highest voltage variation I saw was .5 volts. Is there anyway to diagnose an ECU without just replacing it? Because of the battery codes I'm sure the dealership will insist on a new battery even if it could be the ECU. I have an extended warranty that would technically cover an ECU replacement but I have to have an authorized mechanic diagnose it as such.