hybrid system malfunction : ECU B No. 2 Fuse

Discussion in 'Gen 4 Prius Main Forum' started by ErickRival, Jun 12, 2018.

  1. ErickRival

    ErickRival Junior Member

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    Bought a 2016 Toyota Prius about a month ago and it was working perfectly fine! Until Last Wednesday I got a Hybrid Malfunction System error on the dash while using the A/C. I went to a trusted local shop and he was able to scan the system and a code over the A/C came up. I didn’t get the code number since I would be going to take it this upcoming Thursday since he was so busy and was asking for me to leave it. The code ended up removing on it’s about a 100 miles of not using the A/C and another 100 miles it came up again. Still not using the A/C. Now yesterday I found a cap for the Fuse which was concerning to me why it was out on the glove compartment instead of it being attached. I found 2 abnormal fuses which obviously weren’t original. 1 of them was in the ECU-B No. 2 fuse and the other on the radio if I remember correct. Since the radio is working perfectly fine I focused on the ECU-B No. 2 fuse and noticed it was a 25 amp instead of the required 7.5. I went to auto zone changed it and about 80 miles later the code has not came up. I still have yet to turn the A/C since I want to see if the code would’ve came up again on its own then test tomorrow with using the A/C if that’s what turns the error code back up.(hopefully not).

    With that being said is it possible that the wrong fuse caused the error code to come up? The previous owner said he drove with those fuses for over a year with no problem.
    My other question is what is the “meter” (dashboard?) which also is under the ECU No. 2?
    The reason the fuses were switched was due to a front end accident, that damaged the radiator and shutter grill. So he said his hybrid mechanic fixed it and he never questioned his work since the car was working perfectly fine.
    If you got this far I really appreciate any response, thank you!
     

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  2. Elektroingenieur

    Elektroingenieur Senior Member

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    Just an oversized fuse probably wouldn’t cause a diagnostic trouble code (DTC) to be stored.

    As you may know, a fuse limits the current that can flow in a circuit. If a fuse with a higher rating is installed where one with a lower rating is needed, and the circuit is otherwise working as designed, then the fuse with the higher rating is unlikely, on its own, to cause any malfunction. Indeed, the equipment powered from the circuit generally wouldn’t be able to detect the rating of the fuse at all.

    An oversized fuse doesn’t protect against an overload or fault from some other cause, though. For example, a circuit designed for a 7.5 A fuse might be wired with 0.5 mm² (similar to 20 AWG) conductors, which under some conditions can safely carry 9 A. If equipment on the circuit were to malfunction and draw, say, 23 A, then the 25 A fuse probably wouldn’t blow, but the wire would be overloaded and might melt or even start a fire.
    If the person who did the electrical repairs after the collision put in fuses not only of the wrong ratings, but also of the wrong physical size—preventing the cover from being installed on the bottom of the instrument panel junction block assembly seen in your photo—I’d be concerned about what else might have been done wrong.
    “Combination meter” is Toyota’s term for the instrument cluster: the pair of small displays and constellation of indicator lights under the glareshield.

    That said, I think the listing of fuses and loads you shared may be for a different vehicle: on the fourth-generation Prius, the combination meter is powered from the METER-IG2, ECU-DCC NO. 2, and HAZ fuses, not the ECU-B NO.2 fuse, which powers such items as the A/C Amplifier Assembly, Radiator Shutter Sub-Assembly, Network Gateway ECU, and Hybrid Vehicle Control ECU. (For a complete list, see the interactive Electrical Wiring Diagram, available by subscription to techinfo.toyota.com.)

    It wouldn’t surprise me if the current problem, which I wouldn’t ignore, even if the DTC doesn’t return immediately, stems from a faulty collision repair. With the actual DTC, we might be able to share more advice: each DTC corresponds to a section in the Repair Manual (also on techinfo.toyota.com and in the ChiltonLibrary service, to which your local public library may sponsor free access) with detailed troubleshooting information.
     
  3. alanclarkeau

    alanclarkeau Senior Member

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    I'd agree, it's worth checking. Crash repairers sometimes do the electrical connections themselves. The only problem I've ever had after panel repairs has been electrical - though all were to do with connections of lights or indicators.

    Usually more a problem with older cars. Several older cars I bought (cheap, one a project car, others for the kid's College cars), I ended up discovering a few appeared to have just had random fuses inserted - which I corrected.
     
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  4. ErickRival

    ErickRival Junior Member

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    Thanks for the replies, I wasn’t alerted and just saw them. Thanks elektroingenieure for the thorough description. So the car is still currently at the shop. They came across the code (picture provided under) and shop recommended to switch the battery and if that wasn’t the fix to the problem then they would put my battery back. 50 miles later after they drove the vehicle they were once again alerted with the “hybrid system malfunction” error code and have put my battery back. I’ve mentioned to them to check the ac compressor since that was switched from the previous owner and considering the fuses situation I can’t say they actually installed it properly. With my previous Prius 05 I was able to use Techstream to diagnose a inverter issue in which gave me a sub code. I’m almost 100% the code retrieved should come with a sub code also, so currently downloading Techstream to see if I can figure that out. I don’t know why the shop wouldn’t have been able to retrieve a sub code unless it doesn’t have one.
     
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  5. ErickRival

    ErickRival Junior Member

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    Here is the code from their monitor
     

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  6. Elektroingenieur

    Elektroingenieur Senior Member

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    I’d suggest reading through the diagnostic procedure for DTC P0AA649 in the Repair Manual, available by subscription to techinfo.toyota.com. There are two versions of the procedure, one for NiMH (ZVW50) and one for Li-ion (ZVW51) models. Neither version describes any INF codes for DTC P0AA649, “Hybrid/EV Battery Voltage System Isolation Internal Electronic Failure,” for which the detection condition is “Insulation resistance between the high-voltage circuit and the body has decreased.” There is a fairly long list of possible trouble areas, including—among others—the A/C compressor and its high-voltage wiring.

    If you’re inclined to do your own troubleshooting, you’ll probably need a Toyota Techstream diagnostic system (or equivalent), a megohmmeter, and appropriate personal protective equipment. See the warnings in the Repair Manual, which also gives hints like “When measuring insulation resistance using a megohmmeter, measure the resistance while jiggling the high voltage wire harness.”

    The text and illustrations from the Repair Manual are also available in the ChiltonLibrary service, to which the Los Angeles Public Library sponsors free access for anyone with a library card.
     
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  7. RRxing

    RRxing Senior Member

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    From your photo, this is a 5a fuse, not 7.5a.
     
  8. ErickRival

    ErickRival Junior Member

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    My car has now been fixed and it ended up being the A/C compressor. Yet as I mentioned before when they first thought it was the hv battery they had replaced it and claimed to put my old one back after they received the same error code. Got the car back yesterday and I noticed the hv battery fan is always on now. When I come to a complete stop the fan decreases and once I accelerate my speed so does the fan. I cleaned the filter today but still remains on. Is it normal on the 4th gen? I had the second gen for 4 years and it was very rare for the fan to come on, either driving for 4+ hours (road trip) or extremely hot days.
     
  9. Raytheeagle

    Raytheeagle Senior Member

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    For a 2016, why didn’t you go to a Toyota dealer first(n)?

    Some additional questions:
    • What shop did you use?
    • Was this the same shop as the hybrid mechanic used previously?
    • Wouldn’t this be under warranty?
    • How many miles on your 2016?
    • How do you know they put your exact battery back in?
    • Did you look at the pack they put in?
    Something doesn’t seem right:cool:.

    Good luck and keep us posted (y).
     
    #9 Raytheeagle, Jun 24, 2018
    Last edited: Jun 24, 2018
  10. ErickRival

    ErickRival Junior Member

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    It was in a minor front end accident back in 12/16 with 6,000 miles and considered salvage. Only parts replaced were radiator, radiator support, bumper, headlight, and ac compressor which wasn’t installed correctly. So got replaced. Credible shop in Los Angeles, rather not put their information until it gets resolved. That’s the same dilemma I’m in is if they actually put my battery back, I popped the back seats and found a vin on the battery but after research I haven’t came across anything to see if I can match original batteries vin to car.
     
  11. ErickRival

    ErickRival Junior Member

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    No warranty since it’s salvage.
     
  12. Raytheeagle

    Raytheeagle Senior Member

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    You’ll have to pop the lid and look at the modules to know for sure;).

    Each module has a unique code and knowing how to read those codes will let you know if everything is on the up and up.

    Since the car is salvaged, warranties are out the window, so making sure everything is right would be what I would investigate ;).

    Good luck (y).
     
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  13. ErickRival

    ErickRival Junior Member

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    Thank you!

    Can you elaborate on the unique codes please, such as the location on the modules, and if I were to retrieve the code what do I compare it to, or what’s the breakdown of reading them. I’d really appreciate it.
     
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  14. Raytheeagle

    Raytheeagle Senior Member

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  15. ErickRival

    ErickRival Junior Member

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    Thanks for the info!
     
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