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2005 DTC P0A80 Diagnosis

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Eeyore, Jan 12, 2018.

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  1. Eeyore

    Eeyore Junior Member

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    Hello all, new member here.

    My 2005 Prius gave me some errors this week. After a short trip of about 20 miles, the HV battery was acting a bit strange towards the end. I noticed it drained and charged rapidly the last couple miles. I'm the span of a few blocks in a residential area before the end of my first trip it went from 1 bar to completely full. The car sat for roughly 20 minutes before setting off again. About 1 mile later, the Matter Warning Light, Check Engine Light, the yellow (!) light, and the VSC light popped up on the dash. "Problem" was then displayed on the multifunction display and the info panel shows a red car with a ! in the center of it. I immediately pulled into an AutoZone parking lot that was conveniently next to me. I had an employee check the codes and 12V battery. No codes could be read, so I assumed his scanner wasn't able to read Toyota codes. There 12V battery read 12.3V with the car off and tested in good condition. I then called my local Toyota dealership. Their mechanic said the car should be fine to drive to their location as there was no difference in performance. I chose to park it and troubleshoot it myself, seeing as I am an Electronics Engineering Technician. When I arrived home, 20 miles from point of incident, the car drive flawlessly. No extra noises, change in power, breaking force, or anything in the smallest manner that would hint at an issue. The HV battery did read some odd numbers when driving under electric power only.

    After parking the car, I turned it off, then on again. The VSC and (!) Lights disappeared. The HV battery does seem to drain and fill rapidly and randomly some of the time.

    I read many posts on this forum and others about similar issues. I then purchased an OBDII Bluetooth adapter and the Torque Pro app to check the block voltages of the HV battery and read the DTC codes. I noticed that the majority of blocks were reading 17.7V, a few were at 17.6V, and 2 were at 17.2V (block 1 and 14). The fault chose came back with P0A80, signaling the hybrid battery needs to be replaced.

    So, am I correct in assuming that blocks 1 and 14 are at fault? If so, should I balance them, or replace them?

    This should be a factory replacement battery from Toyota. The previous owner informed us that the HV battery was replaced roughly around 150K miles. The vehicle currently has 230K miles. We live in Salem Oregon, so heat isn't an issue.

    Original errors:
    IMG_20180110_090428603.jpg
    After driving back home and restarting the car:
    IMG_20180110_095640948_HDR.jpg
    After letting the car run for 5-10 minutes:
    Screenshot_20180112-171048.png
    After "force charging" the battery:
    Screenshot_20180112-174839.png
     
    #1 Eeyore, Jan 12, 2018
  2. JC91006

    JC91006 Senior Member

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    You can log onto the Toyota website and check the service records. See if there's a battery replacement around 150k miles.

    Premature failures happen, but it's very unlikely
     
    #2 JC91006, Jan 12, 2018
  3. Dxta

    Dxta Senior Member

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    You're right about the two blocks that are showing below 17volts. In my opinion, they're weak, and if you've hot a prolog charger, you could cycle the pack at once, or get dome hubby chargers to do em. But you sure need to replace those two weak modules.

    PS: As you work on the pack, carefully inspect the voltage sense connectors and wires for corrosion
     
    #3 Dxta, Jan 12, 2018
    Last edited: Jan 12, 2018
  4. JC91006

    JC91006 Senior Member

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    Blocks 1 and 14 usually look like that. They are not in line with the rest. It does not necessarily mean they are bad.

    P0a80 could point to ecu, which is usually not replaced with new battery
     
    #4 JC91006, Jan 12, 2018
  5. Eeyore

    Eeyore Junior Member

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    I checked the service records and there is no recorded replacement of the HV battery by Toyota. Considering this information, I'm not sure if there battery has ever been replaced. If it was, then it was not through Toyota. How would I go about testing the ECU for faults? And what part number is that?
     
    #5 Eeyore, Jan 12, 2018
  6. JC91006

    JC91006 Senior Member

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    If there's no records from Toyota on the replacement, then the code most likely means the battery is bad again. Not related to ECU

    Let the car sit a week and take another voltage reading, you should be able to identify the bad block
     
    #6 JC91006, Jan 12, 2018
  7. Dxta

    Dxta Senior Member

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    I don't think its your ECU that's the problem.

    The code is related to your HV battery pack being weak.

    There's a different code for the ECU

    Grid charge the pack, or disassemble it, and cycle the modules, after getting replacement ones from eBay or anyone over here.
     
    #7 Dxta, Jan 12, 2018
  8. Eeyore

    Eeyore Junior Member

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    Thanks for the replies! I really hope it's not the ECU...

    My college has its own hybrid battery reconditioning equipment and the automotive department owes me some favors. I'm going to try to balance the low blocks before purchasing new ones. I found a seller on Amazon that has them for $37 each and they even offer prime shipping.
     
    #8 Eeyore, Jan 13, 2018
  9. Dxta

    Dxta Senior Member

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    I don't think its the ECU from your codes.

    Get the two bad modules and cycle them, then you've to do same for the rest
    But if you've got no time, then a whack a mole approach, just maybe if you're lucky, might work.
     
    #9 Dxta, Jan 13, 2018
  10. Eeyore

    Eeyore Junior Member

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    Would cycling all the batteries be worth it?
     
    #10 Eeyore, Jan 13, 2018
  11. davecook89t

    davecook89t Senior Member

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    I agree with @JC91006 about Blocks 1 and 14. Our 2007 has shown the same pattern since I first started using Torque Pro a year and a half ago, and the car has never thrown a code. I would check for corrosion first and then balance using the reconditioning equipment before buying replacement modules. You may not need them.
     
    #11 davecook89t, Jan 13, 2018
  12. Dxta

    Dxta Senior Member

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    Depends on your time, and chargers you've got.
     
    #12 Dxta, Jan 13, 2018
  13. Eeyore

    Eeyore Junior Member

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    I've watched the voltages and block one swings out by 500mV.
     
    #13 Eeyore, Jan 13, 2018
  14. TMR-JWAP

    TMR-JWAP Senior Member

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    Are you able adjust your torque display to show internal resistance of each block? That would more than likely help show which block is creating issues for you. Just another data point to verify where the problem is, prior to pulling the pack. And a P0A80 can be caused by the HV Battery ECU. This is the ecu that is installed in the battery pack, not the car.
     
    #14 TMR-JWAP, Jan 13, 2018
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  15. Eeyore

    Eeyore Junior Member

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    I did watch the internal resistance. Everything was the same.
     
    #15 Eeyore, Jan 13, 2018
  16. strawbrad

    strawbrad http://minnesotahybridbatteries.com

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    You want to look at the data while doing a forced charge, not after.

    A forced charge is just half the test. Run a forced discharge also. Add battery current to the Torque display. To run a forced discharge first warm up the gasoline engine so that it can remain off while testing. Turn on the headlights, high beams, and rear defroster. Put the car in reverse and give it some gas but not enough to start the engine. If it's warm out you can also run the AC on max cold. The goal is to put as large a load on the battery as possible. Within a minute or two the voltage of the weak module block will drop off. Codes are set when the voltage difference is 1.2 to 1.3 volts. Usually the discharge test shows the weak blocks more clearly than the forced charge.

    I agree with JC9106 that blocks 1 and 14 often read lower than the rest. The spread on yours is larger than normal.

    Brad
     
    #16 strawbrad, Jan 14, 2018
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  17. Eeyore

    Eeyore Junior Member

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    So I have an extra 2005 Prius with a blown engine. It has a refurbished HV battery. The car has been sitting for a year or so. Can I just swap the packs between the two cars?
     
    #17 Eeyore, Jan 20, 2018
  18. Prodigyplace

    Prodigyplace 2025 Camry XLE FWD

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    You could, but a refurbished (used) HV battery that has been sitting for a year may have issues too.
    Refurbished batteries have not had a good track record for reliability here.
     
    #18 Prodigyplace, Jan 20, 2018
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  19. Eeyore

    Eeyore Junior Member

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    It was running reliably before the engine blew. It was my sister-in-law's car.

    What about the ECU? Can I simply swap the two to rule out or confirm my ECU is toast/good.
     
    #19 Eeyore, Jan 20, 2018
  20. edthefox5

    edthefox5 Senior Member

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    Yes.
     
    #20 edthefox5, Jan 20, 2018
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