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Code P0AFA after HV battery repair, Car is running fine

Discussion in 'Gen 2 Prius Technical Discussion' started by wade101, Aug 1, 2017.

  1. wade101

    wade101 New Member

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    I need some help. I replaced two cells in the HV battery and put everything back together on my 2007 Prius. The car starts but I am getting Red triangle, VSC, Check Engine light, and ((I)) light all came on. The car starts and runs. I drove it around and the hybrid battery does charge. I replaced the 12V Battery because it was bad and I am still getting this error P0afa. I cleared the code with OBDII and pressed the power switch twice without pressing on the brakes so the engine didn't start. after a min I got the triangle and the above errors and code P0afa. I checked the HV battery and I get 220V on the out put and it looks like the gas engine turns off when I stop at traffic light so the car does run on the electric motor. I need some help on what could be causing this. I didn't find anything when I searched the forum for this. Most of the posts say the get this code and their car doesn't start, but mine is running fine. I drove it around for a half hour or more. Please help.
     
  2. fotomoto

    fotomoto Senior Member

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    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.
     
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  3. JC91006

    JC91006 Senior Member

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

    TMR-JWAP Senior Member

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    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.
     
    #4 TMR-JWAP, Aug 1, 2017
    Last edited: Aug 2, 2017
  5. wade101

    wade101 New Member

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    Thanks everyone for your help. I did think about the connections so I took the busbars on both side of the HV battery and Ohmed it each one to the connector to the battery ECU. They are all OK. I reinstalled and tightened all of them again manually. I haven't checked the battery modules under load. I will do that tomorrow.I will try the force charge first and see if the error goes away. One other thing, there was white battery acid corrosion on copper pieces and the busbar. I cleaned everything and sanded them before installing. Could there be damage to and corrosion to wires in the busbar signal cables that go to the battery ECU connector. Even though I Oahmed them out. I had the volt meter on sound and didn't see the actual resistance. Do you guys think I should replace the entire cable just incase there is corrosion inside the cable cover? Thanks again. I will let you know what I find tomorrow.
     
  6. wade101

    wade101 New Member

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    I started the car, cleared the code and put it on D and charged the batteries until it was green. turned it off and on and the code P0AFA came back. i cleared it again and it came back right away. All the nuts on the battery terminals and busbars are tight. I rechecked them to make sure. I am out of ideas now. I will purchase a busbar harness that connects to the battery ECM to see if that works. Thank you all for your help. I will let you know what happened. If you have any ideas please let me know.
     
  7. JC91006

    JC91006 Senior Member

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    Where are you in California?
     
  8. wade101

    wade101 New Member

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    I am in Oakley it is in northern California about an hour east of San Francisco. OK I did some more testing today. I checked each individual battery while the car was running. The two new ones were about 8.1 volt and all the other ones were between 7.7 to 7.9 volt. I drained the two new ones down to 7.5V. Restarted the car and forced charged the battery. All the batteries are around 8.2V now including the new ones. Cleared the code and after a minuet there is a beep and the touch screen says Problem. Then another Beep and Problem again and then the triangle comes on along with VSC and others. Same as before. I disconnected the 12V battery cable and same thing. now I am at loss. Do you guys know what the exact description of this code is.

    Either of the following conditions occurs (1 trip
    detection logic)
    • Voltage at each battery block is below 2 V
    • Voltage of all the battery blocks is -24 to 2V


    What does it mean voltage is below 2 volts and -24 to 2V. Where is this measured?

    Thank you
     
  9. grabjoe

    grabjoe Junior Member

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    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.
     
  10. dolj

    dolj Senior Member

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    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.
     
  11. Beachbummm

    Beachbummm Senior Member

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

    Hometown Hybrids Junior Member

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

    ericbecky Hybrid Battery Hero

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    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?
     
  14. Onemanadajack

    Onemanadajack New Member

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    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.
     

    Attached Files:

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  15. ericbecky

    ericbecky Hybrid Battery Hero

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    Thank you for sharing your problem and solution.

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