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Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by SSimon, Nov 11, 2021.

  1. SSimon

    SSimon Active Member

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    Hello All,

    In August '20, a mechanic (not Toyota mechanic) messed up my '06 Prius. As soon as they were done with their work and I drove it off their lot the dash lit up with these lights. I brought it back and a third party diagnostic came up with POA93. The invertor fluid was found to be low. Since this I have had continual issues with these lights coming on.

    Toyota has been working on this issue since 8-20 as the lights sporadically appear. They see the 12 volt battery was low (at around 10 Volts). They replaced the battery under warranty and the car was operable without incident for a short time. The car has now died out (after throwing the same lights) and was towed to Toyota on Friday. They ran codes and they are C2300, C1241 and C2318. They know the 12 volt is getting discharged or is not being charged adequately yet they cannot find any reason for this. They replaced the 12 volt battery, again, and I now have dropped it off to another Toyota mechanic. Side note: Toyota test drove the car for around 40 minutes and cannot recreate the issue and the battery supply was ok so it's seemingly a slow discharge or slow recharge of the battery.

    Knowing you're speaking to a layperson, does anyone have any insight on what to look for as a resolution to this issue?
     
  2. nancytheprius

    nancytheprius Active Member

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    what was it in for the first time when it got “messed up”
     
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  3. SSimon

    SSimon Active Member

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    I ran over tire shrapnel on the expressway. It dented my front fender. My car was completely operable going into the shop with no issues. Repairs: Bumper, spoiler, bumper cover, license bracket, molding chrome, impact bar, energy absorber, temp sensor, bumper cover fastener, grille, disconnect and put back in headlamps, sight shield, color tint (painting of radiator support), tie bar, splash shields, side seals, lock support, upper tie bar, replace condenser in front of radiator, coolant, radiator insulator, radiator support, replace condenser for a/c, evacuate and recharge a/c, fender liners, pull horn out of the way and put back in, windshield washer reservoir, sensor (under restraint system category).
     
  4. bisco

    bisco cookie crumbler

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    sounds like wiring damage and a short somewhere in those repairs. gonna take a really good tech to find it.
    see if there are any electrical specialty shops in the area.
     
  5. SSimon

    SSimon Active Member

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    That’s what I was afraid of. I did find such a local shop just now. I’m calling them tomorrow. Thanks for the suggestion.
     
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  6. dolj

    dolj Senior Member

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    This sounds like the misdiagnosing of the C1241 DTC. Shame on the Toyota tech.

    My theory is the body shop ran the 12 V battery down while doing the repairs. When they were ready for you to collect, they botched the jump start (or connection of battery charger) but got away with not blowing any fuses**, but instead damaged the DC/DC converter within the Inverter assembly.

    This damage is not enough to stop the DC/DC converter dead, but when it has been running a while, something in the DC/DC converter overheats and shuts down. This causes the car to run off the 12 V battery which in turn runs down. When it gets low enough, it flags the C1241 DTC and triggers all the dash lights. It might also set the buzzer off too.

    Not sure where you will go from here.


    ** Or, who knows, they did blow fuses and the fusible link and replaced them without saying so.
     
  7. SSimon

    SSimon Active Member

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    The Toyota mechanic, and I, initially discussed that the body shop possibly wrecked the dc/dc converter and agreed the low inverter fluid can do this. They said there’s no definitive test to be sure. They also quoted a price of over $3,000 to fix it. An expensive experiment on an ‘06 with almost 200,000 miles. Later, Toyota ruled out a bad dc/dc converter, but I cannot recall why. I’m not convinced it’s not the problem based on the prior low fluid so it’s stuck in the back of my mind as the culprit.

    I do get a high pitched alarm when the dash lights are triggered.

    Updated info from second Toyota mechanic: the new battery that was installed last night by the first Toyota mechanic is already dead today. How does this new info change your theory, if at all?

    is $3,000 a typical price for a dc/dc converter?
     
    #7 SSimon, Nov 12, 2021
    Last edited: Nov 12, 2021
  8. rjparker

    rjparker Tu Humilde Sirviente

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    Good 12v battery and it runs.

    It stays running once it starts.

    Good grief Charlie Brown! Did anybody measure the charging voltage and current while it was in Ready (eg charging)? About two minutes.

    Did anyone run a parasitic draw test on the 12v battery when it is charged and the car is off. Maybe 10 minutes.

    Between the two checks you get an answer and it won't be a bad 12v battery. 90% it's a parasitic draw. Then they have to go beyond auto mechanic 101 and repair it.
     
  9. SSimon

    SSimon Active Member

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    The Toyota notes say “auxiliary battery failed load test w/ bad cell. Replaced auxiliary battery &test drove vehicle for approx. 40 minutes w/ dvom connected to auxiliary battery to monitor charging voltage—-ok (13.93v)”. They also note it was “steady throughout test drive”. Does any of this address the tests you say they should run?
     
  10. SSimon

    SSimon Active Member

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    One more piece of info I neglected to mention: when I arrived at the second Toyota mechanic last night, we powered the car down. We tried to power up the car but it wouldn’t when we attempted it with the key in the slot. One we removed the key from the slot, the car powered up.
     
  11. bisco

    bisco cookie crumbler

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    a para sitic draw test would simply measure how much draw on the 12v with the car off. there is a standard spec to compare with.
    the key fob revelation is another wrench in the works
     
  12. ChapmanF

    ChapmanF Senior Member

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    Settles it then. Your car is oppositional-defiant.
     
  13. rjparker

    rjparker Tu Humilde Sirviente

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    The new 12v battery is unlikely to be bad. But it could be low due to a charging issue or drains low when the car is off.

    The running voltage check is half of step one indicating the dc to dc is supplying charging voltage. The second part of step one uses a clamp on dc amp meter to measure charging current. There are other ways to measure the current but a dc clamp meter is fast.

    The parasitic draw when off "can" use a dc clamp meter to determine if there is a huge draw but the more sensitive and common method is to insert a amp meter in series with the battery cable. This is a little more time consuming but if the off state current is much more than 35 ma (thousands of an amp) the battery can discharge overnight or over a couple of days of non-use. For example we have seen plenty of rear hatch lights remain on and discharge the battery. Often aftermarket equipment gets flakey and draws power when it should not. Even an obd2 device continually plugged in has caused issues. There was a electric power steering module pulling a thousand ma all the time.

    Parasitic draw is normally 10-25 ma but can be higher for a few minutes after powerdown. That is normal. The draw can last longer if the battery has been disconnected as the ecus all initialize. Maybe 45 minutes gradually reducing back to < 30 ma. In the end a sensitive dc clamp meter eliminates the longer time periods when testing parasitic draw.

    A recent "Pine Hollow Diagnostics" youtube video demonstrates a couple of parasitic draw methods. The measurement is relatively easy with the right techniques and tools and is a common mechanic skill. If it is normal the issue can be discounted. If it is high, the skill level to repair goes up.

     
    #13 rjparker, Nov 12, 2021
    Last edited: Nov 12, 2021