beercan

If the battery pack fails completely I believe the car will not run, it has internal safety checks to verify the integrity of the battery pack/hybrid system (in case of accident) and will not turn on unless it passes those tests. The first check is the safety fuse in the trunk. It's not enough to just put the fuse back in, you have to slide it fully to engage it, otherwise the car won't start as you've noticed. Even if the hybrid battery were fully discharged, I believe that the car would still start if the system was intact and use the gas engine to recharge the battery. There are two orange safety plugs, one on the connectors over the high voltage wires and one closing the case of the battery itself. they are removed using the tool built into the end of the orange safety fuse in the trunk (so that you can only remove those covers when the fuse itself is disengaged).

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.