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Weird, intermittent indicator lamps (VSC, Battery, Triangle of Doom, "(!)", and Hybrid System) P0A08

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by HDuncan, Apr 2, 2016.

  1. HDuncan

    HDuncan Member

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    I've been struggling with this one for a while and am finally breaking down to ask for help =)

    Seemingly randomly, these five indicators/icons will suddenly appear:
    Red Triangle of Doom
    Yellow (!)
    Yellow VCS
    MFD Battery
    MFD Car divided by an "!"

    The MFD will usually say "PROBLEM". Then after some time, the battery light goes away, and after turning the car off and back on, the VSC and (!) lights go off, leaving just the large red triangle of doom and the MFD icon showing the car with the exclamation in it.

    Eventually, even those lights will go away as well (sometimes after an hour, other times after a day or two). About a week later, they will pop on again.

    First sign of trouble: Lights and icons show up:
    thumb_IMG_1813_1024.jpg

    After about 20 minutes, the battery light goes away on its own (car hasnt been turned off or on, it just goes away)
    thumb_IMG_1815_1024.jpg

    after turning the car off and back on (within about 1 hr of the lights coming on), the VSC and (!) have gone away, leaving the triangle and the "!car" icon.
    thumb_IMG_1816_1024.jpg


    (as I write this, the dash board shows NO lights or icons), but I suspect they will return....
    ...they always return...



    History:
    Car was just recently, low-speed rear ended, though I can't recall whether this was happening prior to that or after..

    I used an MVCI to look at the codes when it first showed up and pulled the following:
    thumb_IMG_1701_1024.jpg

    I then did a battery load test and the battery wasn't terrible but I replaced it anyway (with yellow top optima). Seemed like everything was great for 4 days then today -- wham, the lights came back on UGGHHHH

    I pulled out my MVCI to see if the lights happen be associated with different codes, but of course tech stream is no longer working (unable to connect to VIM).

    I'm not sure what to do at this point. I could take it in, but I'm wondering whether this issue might be related to the accident, and if not/their insurance won't cover it -- how expensive will it be to fix.

    Seriously appreciate any help!
     

    Attached Files:

    #1 HDuncan, Apr 2, 2016
    Last edited: Apr 2, 2016
  2. bisco

    bisco cookie crumbler

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    how many miles on her? have you tested the new battery?
     
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  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Usually P0A08 means the DC/DC converter (within the inverter) has failed. Usually the converter fails if the car has been subject to a botched jumpstart. Did that occur to your car recently?

    A rear end accident would not impact the DC/DC converter.

    You will also need to figure out why you can't get Mini VCI to work as the presence of the battery icon in the MFD implies the traction battery has failed or is about to.
     
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  4. HDuncan

    HDuncan Member

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    Thanks Patrick! I can't remember jumping the car anytime recently... a long time ago I jumped a car with it, and may have botched that -- but that was 2-3 years ago. Could it have taken this long to manifest?

    The car is a 2005 with 160,000 miles. No major repairs in the past, except I replaced the water pump after it failed and caused overheating.
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    No, a problem with a jumpstart would immediately appear. Regarding the water pump replacement, was that the engine coolant pump or the inverter coolant pump?
     
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  6. HDuncan

    HDuncan Member

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    It was the one that is driven by the serpentine belt, held to the block by 3 bolts. I did that one in my driveway, but I think the other one was replaced as part of a recall.

    Good idea! I let the car sit overnight then used the "Display Signal"/MFD method to check the battery voltage this morning before I drove the car:

    PowerButton pressed once:
    thumb_IMG_1834_1024.jpg

    PowerButton pressed again, with headlights+highbeams, AC AUTO, front and rear defrost buttons pressed:
    thumb_IMG_1835_1024.jpg

    PowerButton pressed again, with brake, putting car in ready mode, engine running.
    thumb_IMG_1836_1024.jpg

    By the way, Patrick and Bisco, I'm searching through threads to learn more about this issue out and I noticed that you both are always jumping in to help other members with their troubleshooting -- just wanted to say thank you so much for everything you do for the members and lurkers of this forum, even when you so often don't get much in return. This forum wouldn't be what it is without members like yourselves =)

    UPDATE: Got Techstream working again!
    There's a great write up that works for me every time on my 64bit computer (attached to this post)

    The only code I see now is good ol' P0A08. I can't seem to find any more information. When I click the little blue icon it takes me to a page called "Freeze Frame Data" with a readout of various parameters.
     

    Attached Files:

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  7. bisco

    bisco cookie crumbler

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    12.2 is a bit low for a new battery. it may not be your problem, but you might want to charge it up just to be sure.
     
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  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. Use a digital multimeter to measure voltage across the 12V battery, or from the dedicated positive jumpstart terminal to body ground, when the Prius is READY. Report the voltage.

    2. If the voltage is much below 13.8V then the DC/DC converter has failed.

    3. If the voltage reading is good, clear the DTC P0A08. Keep the multimeter with you as you drive the Prius around.

    4. As soon as warning lights appear, leave the Prius READY and measure battery voltage again per #1 above. Report the voltage reading.

    5. Upload the freeze frame data as an image.
     
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  9. HDuncan

    HDuncan Member

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    Patrick, I didn't have my voltmeter in the car when it happened today, but will use it to get the readings you requested. However, the light did appear again and I immediately pulled over and used the MFD method. I know it's not ideal but it was all I had at the moment.

    The MFD readings were:
    ACC --- 12.9v
    IG ON --- 11.7v (with Headlights/Defrost)
    READY --- 13.8v


    When I got home, I hooked up Techstream and did a health check. Same codes as before: P0A08 and C1357.
    healthcheck.jpg

    Here is the FFD for both:

    P0A08:
    Page 1
    P0A08 P1.jpg

    Page 2
    P0A08 P2.jpg


    C1357:
    Page 1
    thumb_IMG_1841_1024.jpg

    Page 2
    thumb_IMG_1842_1024.jpg
     
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. Check the tightness of the 12V battery cables, including the negative cable where it bolts to the body. If there is any corrosion between the fender and the negative cable, clean that up.
    2. Check the condition of the positive battery terminal fuse block (remove the red plastic rubber cover to carefully inspect.)
    3. If the above checks do not reveal a problem, and you want to troubleshoot further, get the factory repair manual from techinfo.toyota.com as there are various wiring harness checks that you can do. You can also check the tightness of the inverter cable connections.

    Based upon the 14V reading in the freeze frame, it does not appear that the DC/DC converter has actually failed, hence you need to look for an intermittent connection somewhere.
     
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  11. dolj

    dolj Senior Member

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    A reading of 14+ V could also mean the 12 V battery could be completely flat. I used to see 14.4 - 14.7 V all the time until I changed my 12 V battery. Since changing my 12 V battery I can't recall the last time I saw above 14.3 V. From my observations, 14.4 V supplied by the DC/DC converter means the car thinks the battery is completely flat.

    The images you posted in post #6 pretty much confirm for me that your 12 V battery is less then stellar (my nice way of saying your battery is pretty much dead.). It certainly looks like it finds it hard to hold a charge.

    Hope that helps.
     
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  12. HDuncan

    HDuncan Member

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    Just wanted to post an update:
    I found my DMM, cleared the codes, and will report on the above tomorrow just to make sure I'm not getting biased readings from the MFD signal display method. Once the DTC pops up again, I'll pull over immediately while the car is still in READY mode and report that voltage reading.

    Car drives normally, no symptoms whatsoever. MPG is consistency 42mpg, 75% highway driving.
    One odd behavior is that when the VSC and (!) indicators appear, I can't use cruise control. Once those go away, I can use cruise control again, even if I still have the red triangle.
     
  13. HDuncan

    HDuncan Member

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    Well, Patrick - I tried to clear the DTC but it comes back immediately, like I click the erase button and it blinks off for a split second and comes right back on. It used to be more intermittent but now it seems to be sticking around.

    Oddly, even though the VSC and (!) lights are on, I only see the single P0A08 code.

    Took direct battery measure in the engine bay with DMM this morning after the car sat for the night, before starting the car: 12.61
    In ready mode it was 14.08
     
  14. HDuncan

    HDuncan Member

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    Patrick -- here's an update.
    Lights were intermittent (would turn on and off seemingly at random -- sometimes just the large triangle, sometimes all 3 lights) but have now become permanent. Even if I reset the codes, the lights come on immediately when the car enters READY.

    Responses to your recommendations:
    1.) I basically uninstalled and reinstalled the new 12V battery and cleaned up/tightened everything down. Used battery cleaner on the posts and clamps as well as the ground clamp bolt that goes into the chassis.
    2.) Positive battery terminal seems okay. Checked tightness of the bolt and it seems good. Anything specific I should look for to indicate the condition is acceptable?
    3.) I am beginning to think there might be some sort of electrical short that was caused (or worsened) when I was rear-ended.

    Also -- How do I check the tightness of the inverter cable connections? Is it this:
    from: Dredded pa092 error on 2005 prius | Page 2 | PriusChat
     
    #14 HDuncan, Apr 29, 2016
    Last edited: May 1, 2016
  15. HDuncan

    HDuncan Member

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    Oh, I've also been keeping a log of battery voltages taken from engine bay pos terminal to nearest grounded bolt using my DMM:

    4-8-16
    Light turned off
    READY = 14.28

    4-11-16
    Morning after sitting for a couple days
    READY =14.06

    4-12-16
    After a day on the way home at gas station
    OFF= 13.08 off
    READY =14.55

    4-13-16
    cold start lights back on after days being off
    READY = 14.1

    4-27-16
    After battery clean
    READY = 14.05
     
  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Well, you could try that. Actually, what I had in mind was checking the high voltage orange cables that connect the traction battery to the inverter, as well as the cables that connect the inverter to the two motor generators in the transaxle. However the post you cited is certainly relevant to your car's problem, so you can try what was suggested and see what happens.
     
  17. HDuncan

    HDuncan Member

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    I finally gave up and took the car to the Dealership -- after a couple days and a $385 diagnostic charge, they have settled on it being the DC/DC Converter.

    They want $1,800 to replace the part.

    I called around and got one quote from an independent shop for $5000

    I know this is supposedly a project someone like me might be able to do, but I'm concerned about safety risks -- is there a risk of electrocution when swapping the inverter with a used model?

    Also, I heard it can be pretty painful to bleed the inverter coolant. I've done spark plugs, oil, and TB cleaning. Is this the kind of repair a person like me could handle?

    Any advice is greatly appreciated -- if it's something I should be able to do myself, I'll take photos and make a guide.
     
  18. M in KC

    M in KC Active Member

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    Changing the invertor coolant is a walk in the park compared to changing the ICE's coolant. There are good Youtube vids for it. Sorry can't help you on the inverter swap itself.
     
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  19. HDuncan

    HDuncan Member

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    Looking at some images of the process of unbolting the inverter, I'm wondering at what point the coolant even needs to be changed?

    Spring maintenance
     
  20. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Spend the small amount to subscribe to techinfo.toyota.com so that you have access to the factory repair manual info and the safety precautions, such as removing the orange traction interlock on the traction battery and allowing time for the electrolytic capacitors in the inverter to discharge. Then you don't have to worry about being zapped.

    If you DIY you can probably buy a used inverter for $200 or so, along with investing half a day of your time.

    Draining the inverter/transaxle of coolant is one of the first steps when you want to remove the inverter. The inverter coolant loop is not difficult to refill. The engine coolant loop is the one which can be troublesome if you totally drain the system including the coolant heat recovery system part of the loop.
     
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