Code P0AFA after HV battery repair, Car is running fine

Hmmm.

Sounds like you didn't balance charge the pack after replacing those modules.

Here's what I'd try. Disconnect the 12v or otherwise cancel the P0AFA code. Then perform a force charge: In a safe location with car on and in ready mode, apply e-brake, brake pedal firmly pressed, place in D, and floor gas pedal until you get to a green bar. Drive and see if code comes back.

 

Your should have more codes if the battery modules are bad. I highly suspect the modules you put in may be an issue

 

Although the car appears to be running normally, I would go back and check all the torques on the module bus bars and the output cables. Most likely, you're checking the voltage when it's under no load. A bad connection typically won't show up under no load, but will definitely show up when current starts flowing.

You my end up needing another module or two if the threads are destroyed from arc damage.

I threw a HV battery in my car one time and forgot to tighten the nuts on the two output cables due to some unusual distractions occurring at the time. They were only on about two or three threads. The cable lugs were making contact with the studs only because of cable tension. Drove it 300 miles like that. Car appeared to work just fine, even hitting triple digit speeds. I thought about it during the drive around the 50 mile point but convinced myself there was no way I actually forgot, because I figured there was no way it would run this good if I didn't tighten the nuts. Checked when I got home. Whoops. Only minor arc damage. Nuts threaded right on and torqued just fine.

 

Where are you in California?

 

I know this is an old post, but I wanted to know if this ever got resolved. I have a similar problem on my 2007 Prius. I rebuilt the battery pack and all the codes cleared except for P0AFA. I have to press the power button 3 or more times to get the car started. The ready light will blink and I'll hear clicking from the main relay but the first few times the ready light goes back off. Even when I get it started and clear the P0AFA code it comes back in 30 seconds. I tested the voltage on the battery side of the main connector and got 224 volts.

I'm thinking about looking into replacing the ECU or main relay. Looking for ideas.

 

Seeing as the fortune cookie message for this code is Hybrid Battery System Voltage Low, I would focus first on the sense wires that feed the ECU with the voltages of the battery blocks. Look particularly for corrosion that goes into each wire back from the connector or other signs (maybe not obvious at first) of breaks. It maybe worthwhile replacing the sense wires entirely if you find corrosion or other damage.

 

I wish people would let us know what the final out come was.. Im having the same problem.

 

The problem is typically a fissure or corrosion on the bus bar sensors or a faulty hybrid battery ecu.

 

IIwould place my bet on the items Hometown Hybrids mentions.

Carefully inspect and probe each of the sensing wired at the crimped connection near the ring terminals. Get a magnifying glass if you need it. Or, if you have proper safety equipment, you can probe the connections live while watching the voltage data from your Diagnostic Equipment. (Techstream, Torque Pro, etc)

Unplug the orange connector at the hv battery computer. Inspect the pins and recepticals for any sign of corrosion. It is not uncommon to see green corrosion that has travelled down the wires all the way to the computer circuit board.

And I agree that it is frustrating when we don't hear back from folks. Maybe they weren't wear High Voltage protection when doing their repairs?

 

I too have been searching low and high for this gremlin. I finally found it today. The orange plug to the control module that connects to each of the cells was corroded and broke off. Specifically this is the module inside the hybrid battery case. I replaced it and allgood now. I truly hopes this helps someone else. Thanks. Pics attached.

 

Thank you for sharing your problem and solution.

As I mentioned in my previous email above, the corrosion is a common issue.

 

My orange connector looked like above (second pin from edge broke off), and replacing the ecu fixed the problem.