Just wanted to post a big thank you from across the water. I got the Check Hybrid system at 107,000 miles and dealer wanted $7,500 to replace the traction battery. But after checking around a few other resources and this thread decided to give it a go. Ordered 3 cells from Belarus just to be sure I had extra parts. Took me an hour to remove the traction battery. All of my cells tested at 7.3 - 7.6v though and I didn't have to replace any individual cells. But my copper bus bars were quite corroded. Was quick work with a rotary tool with sandpaper attachment to polish them up and have it reassembled. If it helps anyone though, I used a small power drill to remove and replace the nuts on the bus bars...bad idea. I didn't think it had much torque, but it sheared one of the battery posts off. Doing it by hand it much was more reliable. Another dumb move was in reassembling the unit I forgot that the service disconnect had to be inserted and slid all the way over...dumb. On the other hand, I can now reliably disassemble and reassemble the unit in less than an hour each way. An hour to check and clean the battery and voila. No more error codes. I posted a copy of my bus bar before and after cleaning, it seems this is also a common problem, and not just bad cells.