Error code P0AFA (2006 Prius)

Discussion in 'Gen 2 Prius Technical Discussion' started by Scorpion101, Oct 15, 2017.

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  1. Scorpion101

    Scorpion101 New Member

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    Hi all,
    I own a UK Prius 2006 model with over 90,000 on the clock. In recent months I was intermittently getting the triangle of death light as well as engine, VLC and some others. The car would appear to go into limp mode. After parking for a short time.and returning the lights would have gone off. This happened approx once every couple of weeks. Now they stay on permanently. My odb2 brought back the code P0AFA - Hybrid Battery System Voltage Low. I initially spoke to my dealership who advised me to replace the 12v battery. No joy. I took it to my local dealership for a health check and they told me it needed a new hybrid battery. They had block V01 down to 15.81 where as others were approx 16.20. They quoted me £1859 for a replacement battery. I opted to get a replacement cell online and took the hybrid battery out yesterday. All cells were registering as 7.7 on the volt meter except one which was 7.6. There was a large amount of corrosion on the plates so gave them all a good clean. I replaced the one cell with a smaller voltage than the rest. Put it back together and back in place but again, no joy. I cleared the codes, and they came straight back after 30 secs.

    I spoke to the guy who I got the cell from and he said about balancing the 12v battery with the hybrid battery?? Not too sure what that means.

    Is anybody able to offer any advice as to what could be causing my problem?

    Thanks in advance.
     
    #1 Scorpion101, Oct 15, 2017
  2. Prodigyplace

    Prodigyplace 2025 Camry XLE FWD

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    @jeff652 can advise whether his Prolong system could help rebalance your battery.
     
    #2 Prodigyplace, Oct 15, 2017
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    I don't believe the P0AFA would be triggered by individual modules. You may want to take a look at the integrity of the voltage sensor harness, it's plastic plug/pin receptacles and the pins on the ECU. It's not uncommon for corrosion to buildup in those areas. Unfortunately, it doesn't usually get inspected, as most people focus on the bus bars instead. You've stated the bus bars have already been cleaned, so they should be good to go. Just make sure all fasteners are torqued to 48 inch-lb. (5.4 N-m?) Including the orange output cables that are fastened to the main contacts.

    If the problem is not found in the above areas, look at the rest of the electronics in the battery case.

    Check the integrity of the orange safety disconnect and it's internal fuse. The fuse is bolted in place inside the disconnect.

    Check the main contactors and wiring.

    An, as always, the possibility exists that the ecu is a problem.

    If all else fails to find the problem, turn the car on as if you were going to drive it. If the code is there, trace where the high voltage is lost.

    The battery side of the main contacts will have 210+ volts as long as the safety disconnect is installed.
    The side of the contacts where you attach the two orange cables should have 210+ volts as soon as you press the Start button. If it doesn't then you know one of the main contacts isn't shutting.


    As for balancing the 12v with the hybrid battery, it would be safe to assume there was a miscommunication, or he is clueless. The 12v system is used as control power for operating the relays/contactors/sensors and for powering the ECU.
     
    #3 TMR-JWAP, Oct 15, 2017
    Last edited: Oct 15, 2017
  4. Dxta

    Dxta Senior Member

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    In addition to what @TMR-JWAP has said, you'd need to balance your existing modules, and the one you bought. Replacing it without implementing the cycles, would only be short term. Although some Fox's over here said they've done rebuikts without cycling.
     
    #4 Dxta, Oct 15, 2017
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