Post engine swap: Code P0AA 526 614

Discussion in 'Prius v Technical Discussion' started by RunningOnMT, Mar 13, 2020.

  1. RunningOnMT

    RunningOnMT New Member

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    Hi all,

    After completing an engine swap in my 2012 v, I've got a persistent hybrid system trouble code P0AA, with detail codes 526 and 614. See thread "JDM Engine in a US Prius?" for details on the swap itself, if interested.

    From what I'm reading, 614 indicates "inverter or DC cables". 90% sure this code occurred only AFTER the engine swap, so I'm looking for places I might've messed something up during the process.

    The inverter option seem straightforward enough, but I'm skeptical of that explanation as the inverter was not disturbed during the swap. Push comes to shove, I do have a 2011 liftback as well and I may be able to swap the inverters between them to test.

    The DC cables option I'm less clear on; anyone have any insight into this?

    Are there any tests that I should be running with Techstream to further isolate this?

    The car is running and driving; the only overt symptoms I've observed aside from the MIL are that 1) the "eco" indicator light does not illuminate and 2) the cruise control doesn't work. I'm also only seeing about 35MPG average on the dash, though that may be entirely unrelated. The car will operate in EV mode as well as normal.
     
  2. RunningOnMT

    RunningOnMT New Member

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    After some more reading, I monitored the short wave highest value while first setting the car to on ready off, then ready on, then drive engaged.

    Initial reading was 4.9. As soon as I switched to ready on, it dropped to 1.73. Engaging drive made no difference. This seemed to confirm an inverter fault.

    However, when I switched the car off and then repeated the test, I got 1.73 from the get go (switch on, ready off). Going to ready on made no difference. I then shut the car off, pulled the hybrid isolation plug, waited approximately 10 minutes, then reinserted the plug and repeated the test. Once again, 1.73.

    This is a bit perplexing.

    I then removed the isolation plug, waited 10 minutes, and removed the battery to inverter wires at the inverter end. I grounded one end of my ohm meter on the frame and applied the other end to each of the cables separately, and had open loop readings. This seems to eliminate the cables.

    The inverter in the liftback does not have the same part number, so I'm reluctant to pursue my original notion of swapping the inverters.

    At this point I'm leaning toward the inverter as the culprit, though the somewhat inconsistent testing results are concerning. Open to suggestions for additional test scenarios.
     
  3. ChapmanF

    ChapmanF Senior Member

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    Couple of things:

    • There can be insulation flaws that an ordinary low-voltage ohmmeter won't reveal, but a megger will. The repair manual fault tracing steps call for a megger. They have become cheap enough these days they could even be a casual purchase, but don't get too casual; at 500 volts they can be less healthy than most casual purchases. A document called "A stitch in time..." by the actual Megger company is not hard to find, and well worth reading; it will tell you a lot more about effectively and safely using the instrument than you'll find on the maybe one page of instructions that might come with it from a cheap offshore seller.
    • If you test between the center cable conductor and body ground, you have to make sure that the cable shields are still continuous with body ground at one end of the cables or the other. If you've disconnected them at the inverter, you're relying on the battery end still having the shielding clamped down. On another thread recently, somebody pointed out a sequence of steps in the repair manual, no less, where they showed the cables disconnected at both ends and still said to measure between the center conductor and body ground. There aren't a whole lot of errors I know about in the repair manual, but that is one of them....
     
  4. cnc97

    cnc97 Senior Member

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    I would swap the inverter to see if the problem follows the inverter.
     
  5. RunningOnMT

    RunningOnMT New Member

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    Thank you - this is super helpful. Didn't realize there was such a tool, got one on order. I'll educate myself on the necessary precautions.
     
  6. Joe I

    Joe I New Member

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    All I can tell you is that it's likely not related to your swap. I just performed the same swap with a JDM engine on a 13 V, and I'm not having the same trouble. The only high-voltage things you disturbed should've been the HV battery disconnect and the A/C plug.
     
  7. RunningOnMT

    RunningOnMT New Member

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    I suspect you're correct. Still, I'm always suspicious of apparent coincidences with these things.
     
  8. RunningOnMT

    RunningOnMT New Member

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    Ok, update time.

    It does not appear to be the inverter or the frame wire. I've swapped both, and the issue is exactly the same. Also tested the frame wire with a megger and it tested good. I wasn't fully confident in my results, hence the frame wire swap.

    I'm leaning toward a relay or battery issue. Here's why.

    Looking at the short wave highest value in Techstream, I get 4.98 with the power on and ready off. Foot on brake, press power button to go to ready on, SWHV goes to 1.73ish. Turn car off, repeat test, and now the SWHV is 1.7 while still in ready off. Letting the car sit overnight, the initial test will again show 4.98 until I go to ready on.

    Additionally, the above test goes exactly the same with the HV safety plug removed. If I'm not mistaken, this indicates the issue cannot be downstream of the safety plug, which leaves the battery and relays, no?
     
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