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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. RunnerCNY

    RunnerCNY Junior Member

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    I need to replace the transmission ecm/ecu. Since the dealer is only going to charge $40 labor, I'm thinking it's easy to get to. Does anyone know where the ECM is located? Anyone have a schematic. The dealer wanted $650 for the unit. I'm thinking of getting one from a junk yard. My 2005 Prius has 164,000 miles. (I did have the dealer diagnose the problem--Transmission P lock error. 12V battery is just fine)
     
    #1 RunnerCNY, Jul 16, 2012
  2. Paradox

    Paradox Prius Enthusiast / Moderator
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    Moved from the Prius c forum to the Gen II forum (maintenance section).
     
    #2 Paradox, Jul 16, 2012
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    A reasonable idea to obtain a used unit from a salvage vehicle. It is installed in the dash, on the passenger side. I suggest you subscribe to techinfo.toyota.com to obtain repair manual and electrical wiring diagram info.
     
    #3 Patrick Wong, Jul 16, 2012
  4. RunnerCNY

    RunnerCNY Junior Member

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    Is it behind the glove box?
     
    #4 RunnerCNY, Jul 17, 2012
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    It might be; that is not obvious from the repair manual drawings and I have not needed to find it. An alternate location might be to the right of the radio.
     
    #5 Patrick Wong, Jul 17, 2012
  6. Britprius

    Britprius Senior Member

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    See my post No9 on Gen2 technical discussion "Red triangle light on (PS) off" for ECU positions.
     
    #6 Britprius, Jul 17, 2012
  7. RunnerCNY

    RunnerCNY Junior Member

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    I couldn't find the post. Can you give me the URL? Thanks
     
    #7 RunnerCNY, Jul 17, 2012
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  8. Britprius

    Britprius Senior Member

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    Please see below.
     

    Attached Files:

    #8 Britprius, Jul 17, 2012
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  9. ahmeow

    ahmeow Prius Lover

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    Wow so many ECUs in our Gen 2. Learn something.
    Thanks.
     
    #9 ahmeow, Jul 17, 2012
  10. RunnerCNY

    RunnerCNY Junior Member

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    Thanks!
     
    #10 RunnerCNY, Jul 17, 2012
  11. RunnerCNY

    RunnerCNY Junior Member

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    The Transmission ECU is located behind a black panel just under the glove box. (The ECU is much larger than I thought.) A good yank easily pulls the panel out exposing the electrical connection to the Transmission ECU. Two bolts on either side of the ECU hold the unit in place. The ECU slides out. For my 2005 Prius, the part number is 89535-47010. Average price is about $85. The dealer quoted me $650 plus $50 for installation. Transmission ECU_1.JPG Transmission ECU_2.JPG
     
    #11 RunnerCNY, Jul 18, 2012
  12. Britprius

    Britprius Senior Member

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    Good picture and just about spot on for the diagram.
     
    #12 Britprius, Jul 18, 2012
  13. RunnerCNY

    RunnerCNY Junior Member

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    The diagram you sent me prompted me to unbolt the silver box and "voila" it was labeled Transmission Control.
     
    #13 RunnerCNY, Jul 18, 2012
  14. RunnerCNY

    RunnerCNY Junior Member

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    It wasn't the Transmission Controller. The counter guy at Benwood Auto in Baldwinsville, NY, let me install/test the used unit to see if the light/message would go out. It didn't. I even turned the car on and off quite a few times to see if it would help. So I drove off with the old unit in the car. I'll be calling the dealer back to see about their misdiagnosis. This is a quote from my receipt. "Transmission ECM output voltage is not within threshold. Replacement of the transmission ECM is required at this time."
    I have no driveability problems, gas mileage is normal, and transmission locks in 'P'.
    Any suggestions?
     
    #14 RunnerCNY, Jul 18, 2012
  15. Britprius

    Britprius Senior Member

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    Number 1 suspect the 12v battery. Try disconnecting the negative lead and leaving it a short while then reconnect to see if it clears the dtc. Then check the voltage on the 12v battery.
     
    #15 Britprius, Jul 18, 2012
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  16. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Glad to hear you determined that unit may not be the issue - although a more complete test would have been to disconnect the 12V battery after the replacement unit was installed, to clear the ECU memory. Then reconnect the battery after a few minutes and see what happens.

    Exactly what warning light and message is present?
    What DTC had been logged by your car?
     
    #16 Patrick Wong, Jul 18, 2012
  17. RunnerCNY

    RunnerCNY Junior Member

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    I have a call back into the dealer to get the list of error codes. When I tried out the used module, I didn't clear the codes first. I might go back to Benwood and try that . But first, I'll disconnect the battery, reconnect the battery, and see how long it takes for the error to come back. Then I'll know how long to wait at the parts place. P Lock Error Message_1.JPG
     
    #17 RunnerCNY, Jul 18, 2012
  18. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    That is a classic sign of a weak 12V battery. I know you said the 12V is fine but I've seen this error so many times here and the solution has always been, 12V battery.
     
    #18 usnavystgc, Jul 18, 2012
  19. Britprius

    Britprius Senior Member

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    If you have not already done so check the voltage of the 12v battery this may be your problem as I reported in post 15.
     
    #19 Britprius, Jul 18, 2012
  20. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I agree that the 12V battery is suspect. The OP says that the battery is "just fine". What is your basis for coming to that conclusion?

    If the battery is more than four years old, I would replace that now without further thought.
     
    #20 Patrick Wong, Jul 18, 2012
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