2009 Prius P0A0D error, reset but returned

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Dr Mark, Jul 28, 2023.

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  1. Dr Mark

    Dr Mark New Member

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    newbie Dr Mark here.

    'Check Hybrid System' message. New 12v battery. Carista code reader: P0A0D High Voltage System Interlock Circuit High.

    Paid Toyota dealer (Hadfield Rd Cardiff) for diagnostic. They just told me what i already know, and say "Sorry guv, we only replace the whole wiring loom for £6k.

    This seems absurd. I just need to know WHERE the fault is in the high-to-low circuit is, ie. between which two terminals. I don't think I'm getting what I've paid for, ie. diagnosing rhe specific problem.

    So, is there a wiring circuit diagram for the HVIL anywhere here (2009 prius, gen 3)? This would allow me to ask "have you checked the connection between terminals X and Y?"
     

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    #1 Dr Mark, Jul 28, 2023
  2. Tombukt2

    Tombukt2 Senior Member

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    I think if you search the forums here you'll find the work up for that code I've seen it before
     
    #2 Tombukt2, Jul 28, 2023
  3. PriusCamper

    PriusCamper Senior Member

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    Fastest way to become an expert on this code is to go to Google and enter the following:

    upload_2023-7-28_17-52-5.png
     
    #3 PriusCamper, Jul 28, 2023
  4. PriusCamper

    PriusCamper Senior Member

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    But more to the point, the orange safety plug to the left of the spare tire well needs to be checked to insure it is pushed all the way down and then clear the code and usually that fixes it.
     
    #4 PriusCamper, Jul 28, 2023
  5. ChapmanF

    ChapmanF Senior Member

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    If you've already checked that service plug handle and you're sure that's not it, it's a simple matter of tracing the interlock circuit. Runs from the HV control ECU, to the inverter for some cover safeties there, back to the battery for the service plug safety, then to body ground. The wiring diagram shows the routing.

    Toyota Service Information and Where To Find It | PriusChat
     
    #5 ChapmanF, Jul 29, 2023
  6. Dr Mark

    Dr Mark New Member

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    Right then, FOUR MONTHS after the original fault my 2009 Gen 3 Prius is resurrected from a true Near Death Experience.

    Long story to follow, but short story: Corrosion had infiltrated almost everything, and I needed a Prius-genius friend, £1500, lots of patience and the courage and financial wherewithal to gamble the £1500 since it might not have worked.

    Step 1: Onvious corrosion in the fuse box. £30 second hand, but £500 of his time to replace it using the 461bpage Wiring Harness Repair manual.

    Didn't work.

    Step 2: He gets the massive Hybrid battery out on a bench and finds obvious corrosion everywhere but especially the busbars, with evidence of actual electrolyte leakage. Clean up, replace a few modules.

    Didn't work

    Step 3: Obvious corrosion of the inverter up front, so newer 2nd hand one ordered and fitted. This is now Last Chance Saloon.

    Hallelujah, engine finally starts, no codes. The crowd goes bananas.

    He said this was the closest he's ever seen to actual death. Had that been so, i wouldve paid £1500 to own a dead car worth a few hundred quid. A working one of similar age and mileage is worth maybe £7k (2nd hand prices have shot up I've noticed, maybe the ULEZ Effect?) So I think he's effectively saved me over 10 grand.

    Will compose a proper techie post in the Gen 3 forum some time with his input.
     
    #6 Dr Mark, Oct 10, 2023
  7. bisco

    bisco cookie crumbler

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    Well gov, it sounds like you’re sorted
     
    #7 bisco, Oct 10, 2023
  8. Tombukt2

    Tombukt2 Senior Member

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    Pretty much how I guess I would have done it here and I have all the parts here so I don't have to buy anything which is always good but corrosion I don't know what part of the world your city is in but wow that's a lot of corrosion You must be right on the ocean or something must be in the air.
     
    #8 Tombukt2, Oct 10, 2023
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