P0AA6 256-614 - My attempt to diagnose so far

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by kjermzs, May 25, 2026 at 2:54 PM.

  1. kjermzs

    kjermzs New Member

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    Vehicle:
    2005 Prius
    Model:
    II
    I'm looking for verification that I'm on the correct path to repair this 2005 Gen 2 Prius. It was primarily driven by my step-son and his father while my step-son was learning to drive over the winter. As spring came and it warmed up, the Prius started displaying the red triangle error. Doing some basic troubleshooting, I found there was no turbulence in the inverter coolant tank. I replaced the inverter coolant pump and now I have turbulence in the tank, that issue is fixed.

    I was still occasionally getting a red triangle that became more persistent. I borrowed a friends fancy engine reader and found a P0AA6 256-614 error. I downloaded the service manual and started following the troubleshooting guide, using high voltage gloves. I started on step 19 and found the primary problem on step 21, photo attached.


    I noted that besides the corroded/burnt terminal, all other terminal nuts were suuuuuuuper loose. I had a mechanic diagnose this car about a year ago and suspect they had no idea what they were doing. The car was originally giving me the red triangle and when they returned it to me it wouldn't start at all or give me codes. I found that it was returned to me with the service plug disconnected. after reconnecting the service plug the car has worked until now. I suspect the loose terminal nuts were due to that mechanic doing a shitty job reassembling after attempting to diagnose.

    Anyway, step 21 fails. I am supposed to measure below 1 ohm between the disconnected terminals as shown in the photo. I am measuring OL between all 3 sets of points shown in the photo.


    My plan is to ebay the main relay complete set and the inverter-to-battery wiring harness and replace.

    I'm hoping someone who knows better can let me know if I'm on the right course and if there are any considerations I should be taking. Should I continue the troubleshooting guide just for the sake of physically inspecting the rest of the battery? I have it pulled from the car on a table in my garage right now.
     
    #1 kjermzs, May 25, 2026 at 2:54 PM
  2. kjermzs

    kjermzs New Member

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    2005 Prius
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    additionally, where can I find a guide to replace the fame wire? My youtube search is failing me.
     
    #2 kjermzs, May 25, 2026 at 3:11 PM
  3. PriusCamper

    PriusCamper Senior Member

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    Vehicle:
    2007 Prius
    Model:
    Two
    Howdy... It's so rare for the relays to go bad that most everyone who has worked on Prius for enough years has a spare relay on their shelf because error codes told them it was the problem when it eventually turned out it wasn't. Though based on your photo you might be the exception. I've had one on my parts shelf since 2019 you can have for free you if send me the shipping money soon as I send a tracking number. Just private message me with a mailing address.

    As for wire frame, you're gonna wanna open up the ECU next to the relay and look for corrosion on the pin and clean that up, then replace your wire frame and bus bars. http://www.ACENbay.com makes higher quality voltage sensor wires than OEM. You can either clean your existing nuts and bus bars or buy new from ACENbay. And you get a 10% discount for you if you follow instructions in my signature.
     
    #3 PriusCamper, May 25, 2026 at 8:01 PM
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