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Where is the Transmission ECU located-2005 Prius

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by RunnerCNY, Jul 16, 2012.

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  1. Britprius

    Britprius Senior Member

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    The OP said the dealer said the 12v is fine, that is reason enough to suspect the 12v battery.
     
    #21 Britprius, Jul 19, 2012
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  2. RunnerCNY

    RunnerCNY Junior Member

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    The battery is less than 2-years old and the dealer tested out the battery. I have a call into them to get all the details but they haven't called back yet. The car drives normally.
     
    #22 RunnerCNY, Jul 20, 2012
  3. mikednpv

    mikednpv Junior Member

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    I got that exact same screen about the transmission P lock mechanism right before the 12 volt aux battery died.
     
    #23 mikednpv, Jul 21, 2012
  4. RunnerCNY

    RunnerCNY Junior Member

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    The battery is 1.5 yrs old. This sound like too much BS--any opinions? Here's what the dealer said. The transmission computer needs to be synchronized with the rest of the computers on the system and all the new transmission ecu updates installed. I guess that would be like firmware. They told me that the recycling yard was incorrect and that just plugging in a new transmission ecu will not turn off the warning light. And who's to say the used part wasn't defective.

    Here's what I'm going to do: Go back to the auto recycler and I'm sure he'll let me try out the part again. But this time, I'm going to disconnect the battery, take out the old computer, reconnect the battery, and then plug in the new part. This should be an interesting test. Otherwise, it's $700 to the dealer.
     
    #24 RunnerCNY, Jul 24, 2012
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I suggest you make sure that your 12V battery is fully-charged, using a battery charger, before you do your test at the auto salvage yard.
     
    #25 Patrick Wong, Jul 24, 2012
  6. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    It is BS. Yes it has to be synchronized. All computers have to sync w/ each other. That's how they talk but, they do that every time they power up. I agree that plugging in a new/different ecu will not "turn off" the warning light but, disconnecting the neg cable of the 12V for about 5 minutes will. What he's/she's doing to you is speaking the truth but leaving out the details. Its all semantics.

    Here's what I would do.

    1) Disconnect the 12V battery and completely charge it to 100% charge
    2) Hook it back up and see what happens
    3) If your problem comes back, go to the recycler and try the ecu swap (by disconnecting the 12V, plugging in the new ecu and reconnecting)

    The thing you have to realize is, this must be done in a certain order or if not, you may end up spending money unnecessarily. The priority is ensure a good 12V batt, then ECU. Don't trust what the dealer says about the battery being fine or that its only 1.5 yrs old. Crazier things have happened.

    I'm telling you we've seen this problem b4 and it always turns out to be a low/defective 12V battery. If it doesn't, yours will b the first case I've seen.

    If none of that works, bargain w/ the dealer on the price. I would be utterly amazed if all 3 ecu's were bad and needed replaced. Tell the dealer you don't have $700 and need this fixed as cheaply as possible. The few times I've used the dealer for service, I have bargained w/ them and they did come down on their price.
     
    #26 usnavystgc, Jul 24, 2012
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  7. Britprius

    Britprius Senior Member

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    Plus one for Usnavystgc. Please if you do nothing else at a minimum charge that 12v battery, or post the voltage reading in accessory mode with the headlights on, ideally both. You are being offered sound advise by this forum stop guessing at the condition of the 12v battery, yes we could be wrong but the odds are on our side.
     
    #27 Britprius, Jul 24, 2012
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  8. RunnerCNY

    RunnerCNY Junior Member

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    Here's the battery test using the on board battery test through the display. The battery reads 12.6 V With lights & AC on 11.8 to 11.9V. Switching to the traction batter: 14.0 to 14.1 V. With lights/brights and AC on 13.9V. IS this to low?
     
    #28 RunnerCNY, Jul 24, 2012
  9. RunnerCNY

    RunnerCNY Junior Member

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    I spoke to the auto parts guy at the recycling yard. $75 for the part and I can't try it out after I disconnect the battery to "reboot" the system. Maybe it's worth the $75 if the battery checks out ok.
     
    #29 RunnerCNY, Jul 24, 2012
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    $75 is a reasonable price. It appears that your 12V battery is OK, and it makes sense to try the part to see what happens.
     
    #30 Patrick Wong, Jul 24, 2012
  11. RunnerCNY

    RunnerCNY Junior Member

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    I think I'll take a chance and buy the $75 transmission ecu and disconnect and reconnect the battery to reboot the system before I install the new ECU.
     
    #31 RunnerCNY, Jul 25, 2012
  12. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Good luck. Let us know how it works out for you.
     
    #32 usnavystgc, Jul 25, 2012
  13. RunnerCNY

    RunnerCNY Junior Member

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    I ordered a used Transmission ECU for $55. As soon as I did that, the warning light/message on my car went out and has stayed out. Go figure! At least I'll have a spare ECU. I'm out $55 not $700--a big difference. I'm sure this saga will continue so stay tuned.
     
    #33 RunnerCNY, Jul 28, 2012
  14. Britprius

    Britprius Senior Member

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    Lets hope it stays out and you have no more problems. I still believe this problem comes from the 12v battery but time will tell. Hope it works out ok.

    John.
     
    #34 Britprius, Jul 28, 2012
  15. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    I'm betting it will. If you would have let them, the dealer would have replaced 3 ECU's for nothing. Oh yeah, I forget, they have to be synchronized (yeah, that's the ticket!!! :)).
     
    #35 usnavystgc, Jul 30, 2012
  16. Britprius

    Britprius Senior Member

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    NO I think they would have charge a fortune. I know what you mean rely.
     
    #36 Britprius, Jul 30, 2012
  17. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    What I should have said is "for no reason" vice "for nothing" (lol). You better believe they would have charged him for every ECU.
     
    #37 usnavystgc, Jul 30, 2012
  18. RunnerCNY

    RunnerCNY Junior Member

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    The warning light comes on--goes off--comes on--goes off. No pattern what-so-ever. So I keep driving without a problem and keep the $700 the dealer wanted in my checking account.
     
    #38 RunnerCNY, Jul 30, 2012
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  19. Britprius

    Britprius Senior Member

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    Sounds like a sensible solution to me.
     
    #39 Britprius, Jul 30, 2012
  20. RunnerCNY

    RunnerCNY Junior Member

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    While the warning was off, I installed the used, $55, transmission ECU. (Takes 15 minutes max--two 10mm bolts and one wire harness) After some driving, the warning came on and then quickly went off. I'll keep you posted as things progress.
     
    #40 RunnerCNY, Aug 13, 2012
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