P0B51 - Check Hybrid / Check PCS

OK - a few months ago our head unit just quit - no codes - just quit. That was the first issue of importance on our 2013 Prius.

In the same manner, as we noted on the head unit quitting, I went out to cool the car down before using it, when I started the Prius, the dash showed that the Hybrid System needed checked, as well as the PCS system.

I tried resetting things, useless I now know, and then saw that this is common with HV Batteries in Prius'.

After research here and elsewhere, and trying all the tricks I could find, I dug into the area of the HV battery, actually hoping to find a clogged or burned-out cooling fan. To my surprise, as I removed seats, panels, and covers, I was impressed at how clean the vehicle was, which was why I bought it about 8 years ago. Upon uncovering the squirrel-cage fan, it looked clean and brand new.

My next gut feeling told me to check the HV battery out - I pulled the cover and it looked brand new too. So back to the drawing board and research, and seeing all the issues corrosion causes in the HV battery, I pulled the cover off again, removed the plastic terminal covers, and found what I felt like is/was the problem. So I pulled the back busbars off and they were nasty, went to take off the front busbars, and it seemed like 6-8 terminal nuts were not even hand-tight.

After much consternation, I upped and ordered some nickel-coated busbars and SS Nuts. I'll clean the nickel-plated lead ends with contact cleaner before assembly.

I did not test voltage while the battery was assembled, as my meter only goes up to 12v DC, so I began and tested each model. I was happy and worried, as each module showed between 7.93 and 7.91 volts. I was glad to see the battery pack is probably good, but concerned this isn't the issue I am trying to resolve. I'll know by Saturday evening, it all goes well.

What I would like is brain trust here to give me direction to go if, when the battery is reassembled, the P0B51 code remains, and the pullover and check the Hybrid System and Check PCS system still remains, limiting the car functions.

Oh - and a big thanks for all advice here. I hope to add to the pot of cures soon.

2013 Prius (the one with the larger alloy wheels) - 76,000+- miles

 

Thanks, Brian1954

- I'll check out the ECU connection - just as soon as I find out where it is located. Dang, these newer cars have a lot of modules that have wires plugged into them. Any guidance there. I find a ton of stuff on the 2002-2009 Prius', but nothing for GEN 3 - so far.

I can still remember the dwell and points number on my former teenage ride (32 degrees & D-106 P) 327ci. Impala SS. Looks like a have a lot of catching up to do.

I'll keep the forum updated - with a final conclusion and results, with loses and wins.