P0A0D-350 High Voltage System Interlock

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by GreenTea&SaltWater, Jun 9, 2021.

  1. GreenTea&SaltWater

    GreenTea&SaltWater Junior Member

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    2010 Prius - A couple weeks ago the “check hybrid system” notification came up on the dashboard and a bunch of lights came on but the engine was still running. When I tried to start it two days later the engine wouldn’t start. And now there were even more lights on the dashboard, including the “check hybrid system”. 1.5 years ago I had a P0A80 where I had to replaced some battery cells to make the hybrid engine work again. But this time it’s different cause now the engine won’t start at all. The 12v is fine I had it tested.

    Today I was able to hook my car up to my laptop with a copy of TechStream and got some codes. One of my tire pressure sensors is off, something with the smart key sensor, and the permanent P0A80 to replace hybrid battery. And then there is the P0A0D code. When I click on it it shows me the following page - P0A0D -350 High Voltage Interlock System. In the slide where it shows the voltage battery readings there are two highlighted batteries that read 15.30V. Does this mean anything? Also, cell block #6 is reading at a voltage much lower than the rest at 15.11v, could this be an issue? Since my engine isn’t running I can’t test the batteries under load.


    Searching up the P0A0D code online doesn’t bring up any concrete answers, very ambiguous. But I’ve yet to find a single result for the P0A0D -350 High Voltage Interlock System message in completion on Google.


    So someone mentioned to me that their Prius had an issue where the dashboard looked exactly the same. They said they were driving the vehicle when it suddenly stalled out engine turned off dashboard lit up. Took it to Toyota and they repaired it for free because it turns out it was a recall with the IPM “intelligent power module”. Image attached from the recall notification on my OBD tool. “Toyota motor engineering & manufacturing (toyota) is recalling certain 2010-2014 toyota prius and 2012-2014 toyota prius v vehicles. Excessive voltage in the intelligent power module (ipm) within the inverter may cause the hybrid system to shut down, causing the vehicle to stall while being driven.”


    What catches my attention is the “excessive voltage in the IPM” which sounds similar to the issue TechStream is telling me “high voltage interlock system”. Are those 2 battery voltages it has highlighted at 15.30v maybe telling me that there’s a high voltage error there or something? Also I tried resetting the codes but the P0A0D stayed.
     

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  2. Raytheeagle

    Raytheeagle Senior Member

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    To further diagnose the issue, I'd spend $20 and get the correct troubleshooting tree for P0A0D from tech info ;).

    That will tell you what the next troubleshooting steps are for the 350 INF code:).

    Could be something simple and for $20, you get the correct steps to go about it(y).
     
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  3. TMR-JWAP

    TMR-JWAP Senior Member

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    For the Gen 2, the P0A0D code signifies one of the HV safety interlocks is triggered. There are 2 interlocks, hopefully the info is the same for Gen 3.
    1. the orange interlock on the HV battery (designated as "#2 interlock switch" in the manual). This interlock is made up when the third step of the plug installation procedure is completed. When pushed downward, the switch inserts a shorting wire across two pins at the bottom of the socket.
    2. the second is a switch that is made up on the inverter (under the hood) when the it's cover is properly installed (designated as "# 1interlock switch" in the manual). This circuit is completed when a metal pin on underside of the cover lid slides into a set of contacts as the cover is fastened into place.
    There are 2 subcodes available:
    1. 350 signifies the fault was triggered while the car was not moving and will disable the car
    2. 351 signifies the fault was triggered while the car was moving and will not immediately disable the car
     
    #3 TMR-JWAP, Jun 9, 2021
    Last edited: Jun 9, 2021
  4. ChapmanF

    ChapmanF Senior Member

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    Right, there's one "high voltage interlock" circuit that goes through a few safeties in series. "High voltage interlock" is kind of a tricky name: it's a run-of-the-mill low-voltage circuit. Its purpose is to detect if any of the covers giving access into the high voltage system aren't secured, and keep the high voltage locked off if so.

    The circuit runs from the Power Management Control ECU to the inverter, where it goes through some contacts on the undersides of the wiring access covers there, then from the inverter back to the traction battery, where it goes through a little switch on the orange service plug, and from there to a junction connector and to body ground. If that circuit is broken at any point, you will get the interlock code and the high voltage will stay disabled for your safety.
     
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  5. GreenTea&SaltWater

    GreenTea&SaltWater Junior Member

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    How can I troubleshoot this and inspect the wiring connections?
     
  6. GreenTea&SaltWater

    GreenTea&SaltWater Junior Member

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    Hey JWAP do you know how I’d be able to inspect the connections and wiring?
     
  7. ChapmanF

    ChapmanF Senior Member

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    A person who wanted to do that efficiently would find the circuit in the Electrical Wiring Diagram, and follow the troubleshooting steps for the P0A0D code in the Repair Manual, both of which can be obtained in any of the ways Elektroingenieur kindly described on this wiki page.

    For safety, don't forget that even though it's a low-voltage circuit, all the covers and switches where you might end up inspecting it would put you in close range of high voltage.
     
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  8. GreenTea&SaltWater

    GreenTea&SaltWater Junior Member

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    Anything else I should know? Also what are the chances it isn’t the Intelligent Power Module then?
     
  9. mr_guy_mann

    mr_guy_mann Active Member

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    Going by ChapmanF's description of the interlock circuit, it has no involvement with the intelligent power module.

    For now, get a copy of the service manual, start reading the code description, test procedures, and wiring diagrams. Then you can ask questions.

    Posted via the PriusChat mobile app.
     
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  10. Grit

    Grit Senior Member

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    pulease, manual is just another man’s opinion. Plug n pray is the way!!!
     
    #10 Grit, Jun 9, 2021
    Last edited: Jun 9, 2021
  11. TMR-JWAP

    TMR-JWAP Senior Member

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    Sometimes you can also keep it simple, initially.
    Have you or anyone else ever messed with the inverter cover?
    Have you or anyone else ever messed with the HV battery interlock switch?

    If so, those would be reasonable places to start looking just to make sure it's not something quick and easy.
    One end of the HV Battery interlock switch socket will have a small socket where a two wire harness plugs in. That 2 wire harness is the wires that get shorted when the interlock is installed. Verify that is connected properly and that the pins didn't get bent during any installation/removals.
     
  12. AzusaPrius

    AzusaPrius Active Member

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    Could be easy as replacing those blocks that are low voltage.

    Ebay is the way to drive another day.
     
  13. ChapmanF

    ChapmanF Senior Member

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    A code about the interlock circuit is not related to any battery module voltages.
     
  14. AzusaPrius

    AzusaPrius Active Member

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    He mentioned there were blocks with low voltage.

    These types of issues can cause random codes to pop up.
     
  15. ChapmanF

    ChapmanF Senior Member

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    There are people on this board who argue that low 12 volt battery voltages "can cause random codes to pop up", and the basis of their claim is that the 12 volt system powers the car's computers. The likelihood gets strongly exaggerated, but at least they've got a potentially plausible starting point.

    As far as I've seen on PriusChat, you've now taken the honor of being the first to suggest that a traction battery block voltage, being measured for diagnostic/reporting purposes by a computer that is powered from the 12 volt system, "can cause random codes to pop up" anywhere.
     
  16. Ed Beaty

    Ed Beaty Active Member

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    "These types of issues can cause random codes to pop up."

    Um, sir, could we have a reference to back up this conjecture? Thanks.
     
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  17. TMR-JWAP

    TMR-JWAP Senior Member

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    No they can't.

    Now that I'm home and have time to look at the photos, there's some wonky stuff in there. Things that jumped out at me:

    The freeze frame data:

    The 2 values of ambient temperature...is one 88F and one 419F?
    The 2 values of intake air temperature...is one 91F and the other 32F?
    The MAP (read in PSIG) one is -2 and one is -15?

    The first values, I can believe (88, 91, -2). The others? Not so much. If I was reading those values correctly, there had to be some whacky electrical transient? ECU glitch? idk if that kind of transient would be caused by the P0A0D opening the main HV relays. If I'm misreading them, then ignore my comments.

    The live screen data:
    None of your HV battery block voltages are abnormal.
    Your aux battery is 11.5 volts. Although this is within Toyota's 'tolerance' for performing troubleshooting, charge it, test it or replace it if needed before you end up chasing your tail.
     
    #17 TMR-JWAP, Jun 9, 2021
    Last edited: Jun 9, 2021
  18. AzusaPrius

    AzusaPrius Active Member

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    @chapman

    Hey look there is that code c1259 that goes away by replacing the bad modules.
     
  19. mr_guy_mann

    mr_guy_mann Active Member

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    Huh? What would that have to do with the OP's P0A0D-350 code?

    Posted via the PriusChat mobile app.
     
  20. mr_guy_mann

    mr_guy_mann Active Member

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    Possibly good point on the freeze frame capture- specifically how the B+ voltage reading drops from 11.67V to 11.44V in the next frame.

    Posted via the PriusChat mobile app.
     
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