Won’t Start, Desparate

Sounds like HV is failing . But usually that means that ice engine is going to be running all the time and you're going to be getting 34 to 37 miles to the gallon so that is kind of interesting.

 

P0AFA is a code about failure to properly sense the battery block voltages. You don't get this code because the battery is old and tired and the block voltages are drifting a bit out of spec. You get it when some of the block voltage readings are patently bogus, usually indicating a bad no. 2 frame wire, or its connection plugged in at the battery ECU.

 

I recommend being afraid to chase things inside the high-voltage battery, at least until you have completely absorbed the way it is put together and the precautions you need to work on it safely.

You could start by looking at these troubleshooting steps for the P0AFA code.

You will notice it talks about checking the "busbar module", also known as the "no. 2 frame wire" (don't call it "wire frame no. 2", that's something people do when they don't grok alphabetical catalog names with commas. If you see it in a parts catalog, you might see "wire, frame, no. 2", but that's just the name turned inside out with commas so it alphabetizes with "wire" instead of "no.".).



That frame wire carries voltage samples from across the battery modules back to a connector at the battery ECU, which measures them.

Bad Things can happen to it, or to the battery ECU connector where it plugs in.

 

I had never looked inside of one before so I just lifted up my back carpet and tray took the top off the battery with the orange plug out of course. And then flip down all the plastic covers on that exposed the bus bar nuts and then my '05 almost all of them were frosted quite well and the battery was failing miserably and it was a green tech rebuilt thing from Charlotte North Carolina in 16 or 17 and it failed in 21 not too bad. I figured something caused the frosting not sure what didn't seem like the car gets wet or anything in the back it's bone dry and looks like it's never been damp so I have no idea this car's been parted out and is almost stripped now It had dents in it really wasn't worth fixing It would have been a good beater for a service vehicle and that was about it. On my '09 when I put the new battery in and I mean new battery I sprayed the bus bar nuts on both sides with the CRC red spray that I use on other battery terminals and connections and I have not fully put the back end of the car together so I can take a look in there every so often and right now after 4 or 5 months they're still all red and look like they're supposed to and working great.

 

When introducing things to a new member, it's good to put a little extra emphasis on a few things, like:

• Pulling out that orange plug is important preparation for working on parts of the high-voltage system outside of the battery itself. Pulling it makes the rest of the high-voltage system safe to work on (as long as you wait long enough, after pulling it, for capacitors in the inverter to bleed off).
• Pulling that orange plug is not all you need to think about for working inside the battery itself, and especially not if you are going to flip down those plastic bus bar covers.

Another member here quite recently learned that lesson by vaporizing a bus bar and ruining a couple battery modules. No injury, fortunately.

 

Most folks are genuinely afraid of electricity they cannot see it and costly tools to measure and locate it. But usually that orange plug out and go wash your hands and get a drink and most everything is subsided enough where you can do what you need to do.

 

Except inside the battery itself, where troubleshooting for P0AFA has to take place, and we've already had one person learn that this way:



so we may as well help pjmc09 not have to learn the same thing the same way.

 

The capacitors bleed off faster than that. It's in the repair manual; minutes, not hours.

For a P0AA6, though, you have to remember that "pull the disconnect" does not protect you for the kind of inside-the-battery troubleshooting we're talking about here. With the disconnect in, your battery has 27 live potential 15-volt loops, and any of those can source enough current to do what you see in #9. When you "pull the disconnect", you open one of those 27 potential loops, and all 26 others remain live. On top of that, because of the P0AA6, you know there is at least one live current path in there that the engineers did not plan and couldn't warn you about. Another PriusChat member has just, I hope, treated his still-breathing nephew to a very fine dinner after a brush with one of those.

Need to be on your very best behavior when working inside the battery with a P0AA6.