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Various issues; told they originate with a failing battery & ECU

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by kaiz, Jun 9, 2024.

  1. kaiz

    kaiz New Member

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    2008 Prius
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    II
    To preface - the car is an 08 gen 2 with just under 250k on it. For the past few years it has had some intermittent issues (1-2x a year) symptomatic of a failing combination meter (dashboard not lighting up on first startup, and further issues shutting off if the car is driven with the dashboard dark.) It only happens when it is cold out and I know a couple workarounds so I have not replaced anything there. And after a lot of P0A80 issues and inability to start the car without clearing the code, it had a gen 3 battery swapped in last year and brand-new wiring harness. I was aware of some compatibility issues between generations but thought we worked around them appropriately. It drove decently for a bit, and I had not seen P0A80 since the swap nor experienced an inability to start the car. I've had a few times where the car display information shows the battery drained, and the accelerator drags when I step on it, but obd2 shows that all of the cells are fully charged. Efficiency usually long-term averages 38-41mpg.

    It has had all of the following over the past few months:

    • c1249
    • c1310
    • No code, but flickering tail light. I thought the bulb was failing, but when I went to buy a new one, the auto store employee was extremely helpful and checked it out and told me the light was still good and it was probably a wiring issue.

    A few weeks ago, I got the P Lock Mechanism issue and had the following codes turn up as well

    • c2300
    • p3000
    • p3102
    • The check engine light and red triangle came and went intermittently while I was waiting for my appointment.
    I took it into the Toyota dealership (mistake #1). While I was dropping it off, the service advisor saw the check engine light on in the car and at first told me there was probably something wrong with the engine. They contacted me to tell me the battery needed to be replaced and the ECU was failing. They sent me a screen shot of P0A80 (I thought I was done with this code and I haven't seen it in nearly a year). I asked to have the full diagnostic report and they have given me the run around and failed to present it. I asked for more information on the failing ECU and they have given me further run around on the matter. They were not able to tell me why they believed the ECU was failing, could not provide me with any proof or indication of it failing, or any diagnostic documentation whatsoever. A couple employees at the dealership implied and/or stated directly they didn't know what they were doing, and they quoted an FU amount to replace both, so I was really leery of having the work done. I repossessed the car and have not had any work done on it, but have made an appointment with an independent mechanic for a second opinion.

    I reviewed some other threads and reddit posts and have found a few others with similar problems, with suggestions of parasitic drain or wiring issues. I am getting a second opinion from a real mechanic in a couple weeks (they didn’t have anything sooner) but in the meantime was hoping for a third opinion so I can mentally prepare ($$$) for the verdict. Does this sound like a failing battery & ECU?
     
    #1 kaiz, Jun 9, 2024
  2. ColoradoCrow

    ColoradoCrow Active Member

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    Location:
    Leawood, KS
    Vehicle:
    2008 Prius
    Model:
    I
    Hi. Well if you keeping this car and want to invest in it life. Texashybridbatteries.com does an excellent combination meter repair that is WELL WELL Worth it. IMHO. Also When my 12 volt battery died I had all kinds of codes. Those batteries last about 4 years in a hot TX or FL environments. Id make sure your 12 volt is in great shape and the ground nut is tight to the body panel. Was the third Gen battery new? If not...it could be failing if it was aged. Again If you want to keep the car long term. A New Hybrid battery is worth the investment. Either OEM or Project Lithium. Both will cost about $1900-$2400. But then you should be good for 10 years.
     
    #2 ColoradoCrow, Jun 9, 2024
  3. Tombukt2

    Tombukt2 Senior Member

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    I second the Texas hybrid thing unless you are competent soldering station operator and desoldering guy and can handle all that seriously then don't even fool with it the $150 or 160 bucks you'll have in it after you return your old one is money well spent I've done it here We have four of these cars I've done it the other way by taking them out of other cars too The Texas hybrid solution works without fail once they take care of the capacitors and what not You will not be dealing with this again this creates a bunch of other intermittent problems I drove with this situation for over 2 years I can tell you all about it I'd rather not. The generation 3 battery and the generation 2 is not a thing you mean you have the rack of modules clamped up from a generation 3 in your generation twos battery case because that's not swappable per se You need the case from the generation to the fan arrangement and the front end arrangement with the ECU so dropping in a generation 3 battery wouldn't be a thing using the modules is quite a different thing The code that they pulled for the battery could be permanently stored in your computer I have a generation 3 with the same problems had the battery replaced twice supposedly you can drive this out but we have an attempted or done anything it's just sitting in the memory. So the car runs fine. The p lock issue you can take a look at the blue wire coming out of the white plug I think it's the fourth wire in at the very top of the plug and receptacle in the fuse box It has a cover over it there are pictures all over the net and here about a jumper wire from the p lock fuse. To this blue wire making it have 12 volts so you can activate the solenoid I guessed it undoes the parking lock
     
    #3 Tombukt2, Jun 9, 2024
  4. fragglestickcar

    fragglestickcar Member

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    I presume you mean you had gen3 cells installed, not the whole gen3 battery assembly that includes the ECU.

    I'd start with the simplest explanation which is last year's battery reconditioning (swapping in those gen3 cells) lasted for as long as they usually do -- about a year. The P0A80 tells you that much, but says nothing about a failed ECU.

    As for your combo meter and all the other codes, yeah, welcome to the misery of old cars.
     
    #4 fragglestickcar, Jun 9, 2024
    bisco likes this.
  5. maleko

    maleko Member

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    I have had a failed combo meter on my 2008 2nd gen since 2014 and it has not caused any issues besides the obvious: no speedometer, odometer, or fuel gauge, etc. So I'd say you can probably set that aside for the time being.

    Just my $0.02
     
    #5 maleko, Jun 15, 2024
  6. ChapmanF

    ChapmanF Senior Member

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    The combination meter failure is a widely known and discussed issue for gen 2. It can have a number of effects, including trouble turning on the car, and trouble turning OFF the car. If you've not had "any issues besides the obvious" you've been lucky, but the OP is reporting a bunch of symptoms that are known to be associated with the combination meter.

    It's an easy fix and ought to be fixed, so the OP doesn't have to keep dealing with those issues while also figuring out whatever else the car needs.
     
    #6 ChapmanF, Jun 15, 2024
    Brian1954, maleko and Tombukt2 like this.
  7. Tombukt2

    Tombukt2 Senior Member

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    This is an inexpensive issue One of the cheaper ones you will do on any of these kinds of cars a screwdriver some plastic spluges and an hour and a half of your time or so and you can replace this part with the part from Texas hybrids and not have this issue The rest of your life with the car however long or short that may be it's a good idea I have several that I did not fix and one that I did and the one that I did fix was quick painless and easy messing with the workarounds for the other ones well takes time and playing around and maybe some of you don't have that In that case do the fix and be done It's an easy one
     
    #7 Tombukt2, Jun 15, 2024
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