P0AFC... Terrible Wire and Voltage Module Corrosion

2012 Prius V, 204k miles

Hey everyone…I just wanted to share my recent adventure with the Prius. It has been a while since I’ve been on the forum.

June of 2023 I had a battery failure in my hybrid system. I replaced modules 1 & 2 (block 1) (some people refer to them as packs or cells…I truly don’t know which is correct). All of the buss bars were cleaned. The primary ground cable (attaches to module 1) was very corroded. I ended up peeling back the insulation only to find the cable was so corroded it was actually brittle. I replaced that cable. I did notice corrosion on several of the voltage sensor wires/terminals so they got a little attention and were also cleaned. After putting it back into service…all was good! NOW…let’s jump ahead one year…

This past Sunday, were ready to go to Church, and as soon as things lit up, I had lots of warning lights come on. I had the P0A80 code. Dr. Prius was showing a failure on blocks 2 & 3 (modules 3-6). I ordered some used modules. I was so sure it was cell failure…that I didn’t even load test the suspect cells (that was dumb on my part…so no comments are necessary about that!) I installed the four modules but was again concerned about the visible corrosion on the little voltage sensing wires where they solder to the connector (at the battery end). We put everything back in the car and brought the system up. No Joy! Dr. Prius was showing the same thing as before but it now included the P0AFC code (Hybrid Battery Pack Sensor Module) along with the original P0A80. I hooked up my TechStream (should have done that at the beginning of this event). Block 1 was 0 volts, block 2 was 1.87 and block 3 was 24.98! Blocks 4 through 14 were all around 15.30 volts (which is all good).

I removed the Sensor Module and noted corrosion on two of the terminals. The male plug had a crack in the plastic at the worse one and the same two pins were very corroded. I used my volt meter to read the block voltage between and then attempted to read the voltage at between the blocks and the terminals on the male plug. What a mess… The wires were so corroded that there was virtually no reading from the battery terminal to the plug on the end of the sensor wire cable (where it plugs into the Sensor Module). Obviously the corrosion had moved through the wire and into the plug and then into the Sensor Module itself. Inside the module was a lot of corrosion on the pins and on the actual PCB (circuit board).

So, I have ordered a refurbished sensor cable assembly and a module. I am in hopes this will take care of this problem. I will update once those are in and installed.