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2005 Prius ECM replacement reprogram.

Discussion in 'Gen 2 Prius Technical Discussion' started by Brandon Mason, Jun 19, 2019.

  1. Brandon Mason

    Brandon Mason New Member

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    Leavenworth
    Vehicle:
    2005 Prius
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    One
    I just recently replaced the ECM due to a bad lead causing it not to read my position sensor. Now I'm getting a code that says lost connection with ECM, which I expected. I can not find a reprogram or repairing procedure anywhere... Any help would be awesome!!
     
    #1 Brandon Mason, Jun 19, 2019
  2. landspeed

    landspeed Active Member

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    If it was the lead, is the original ECM still,OK?

    ECUs can be reflashed via tech stream and .cuw files - from Toyota - but immobilisers are another issue and I don’t know how to fix that issue
     
    #2 landspeed, Jun 24, 2019
  3. Brandon Mason

    Brandon Mason New Member

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    Location:
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    Vehicle:
    2005 Prius
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    One
    The original ecm was okay, but the sensor wasn’t getting any voltage for the crankshaft position sensor. I tried the reset procedure where you jump the obdII and let the car go on acc mode for 30 minutes with no luck. I’m not sure how to swap the e proms still trying to find information on that.
     
    #3 Brandon Mason, Jun 24, 2019
  4. ChapmanF

    ChapmanF Senior Member

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    I don't think there is any reprogramming/repairing needed for the ECM. I'd hunt for some other problem.

    Between the HV ECU and the immobilizer, there is a pairing relationship, but you didn't swap either of those. IIRC, they re-pair just by leaving the ignition ON for 30 minutes without trying to start. Or maybe that was just for Gen 1.
     
    #4 ChapmanF, Jun 24, 2019
    landspeed likes this.
  5. landspeed

    landspeed Active Member

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    I didn’t know it was just the HV ECU that linked to the immobiliser - that is good to know!

    Can you let us know more about what happened, and what was wrong with the old ECU? Which ECU was it? Did the old one lose communication? If not, could it be a bad replacement ECU? Was the wiring loom damaged in any way?

    If it was the HV ECU then pairing it might be needed - but it seems the engine ECU and others won’t need that.
     
    #5 landspeed, Jun 24, 2019
  6. landspeed

    landspeed Active Member

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    Do you still have the original ECM? Also, when you say it wasn't getting voltage from the crankshaft position sensor, could it be somewhere between the sensor, and the wiring, or was that checked out to be OK? (e.g. is the fault something on the original ECM circuitboard?).

    It might be worth putting the original ECM back in and seeing if is still unable to communicate, assuming the ECM isn't doing anything like shorting out the connected sensors. If the original ECM can communicate, then it points to bad luck with the new ECM being faulty in some way?
     
    #6 landspeed, Jun 24, 2019
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