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Sudden power loss while driving

Discussion in 'Gen 2 Prius Main Forum' started by prius-survivor, Mar 26, 2021.

  1. prius-survivor

    prius-survivor New Member

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    Hi PriusChat,

    Long time lurker, first time poster. This forum has helped me do so many repairs on my Prius in the past.

    Today I was driving my '07 Prius when the power suddenly cut out and the car could not turn back on. I coasted the car off the freeway and managed to get to a traffic light. Emergency hazards work, the remote key fob can lock/unlock the car, but pressing the power button does nothing.

    I attempted to disconnect / reconnect the 12V, but no luck there either, so I towed it to a mechanic nearby.

    From reading forum threads here, it seems like there's a large chance this is from a blown AM2 fuse caused by a bad inverter coolant pump (I can confirm that the coolant pump has been acting up, and I had been meaning to replace it). However, the mechanic told me that their diagnostics revealed no blown fuses. As far as I know, no engine codes either. What's even more strange, they said all they had to do was "reprogram the ECU" for the car to be working again. As far as I know, the ECU is reset when the 12V is disconnected, so I'm even more confused since this is exactly the first thing I tried.

    Needless to say, I'm a bit unsatisfied with this diagnostic, since I was hoping for more of an answer for ~$300 (150 initial diagnostic, and then another 150 for "extra" diagnostics relating to the hybrid). Do you guys have any ideas what it could be?

    Thanks so much!
     
    #1 prius-survivor, Mar 26, 2021
    Last edited: Mar 26, 2021
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  2. dolj

    dolj Senior Member

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    I think you are correct to suspect a failed inverter coolant pump and a blown AM2 fuse.

    Isolate the failed pump by disconnecting at the plug shown below.
    Prius Gen II Inverter 3 Power Connector.jpg


    The location of the AM2 fuse (15A) is shown below. Pull it and test for continuity with an ohmmeter.
    Prius Gen II Inverter 2 AM2_Fuse.jpg

    If it is blown replace it to get your car operational. Drive it under 45 mph to a better mechanic if you cannot change the inverter coolant pump yourself.

    Let us know how you get on.
     
    #2 dolj, Mar 28, 2021
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  3. prius-survivor

    prius-survivor New Member

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    Hi guys,

    I got the car back from the mechanic today. No blown AM2 fuses. Here are the DTC codes they provided:

    - B1650, B1271, C1242, C1256

    In addition to this, they said reprogramming the BCM (not the ECU) made the car start again. What does reprogramming the BCM mean? Whatever it was, it cost 200 dollars.

    The C-codes seem to be brake related, and I still think there could be something wrong with the inverter coolant pump. Could something weird in the brakes cause sudden power failure?
     
    #3 prius-survivor, Mar 29, 2021
  4. prius-survivor

    prius-survivor New Member

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    Update: I just checked the coolant reservoir and there was little to no visible flow.

    There's no coolant pump related codes. Should I change the pump anyway?
     
    #4 prius-survivor, Mar 30, 2021
  5. dolj

    dolj Senior Member

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    There are no pump-related codes, the closest you get is the Inverter Cooling System Performance (P0A93) DTC which alerts you to the fact the Inverter is getting too hot. You won't necessarily even get this if it is cool out, and/or you are driving fairly sedately at low (inner-city) speeds.

    If there is no coolant flow observed in the inverter coolant reservoir, then that is a pretty sure sign that the inverter coolant pump has failed. It is time to replace.
     
    #5 dolj, Mar 31, 2021
  6. w2co

    w2co Member

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    I think by "BCM" he means battery control module. There should be absolutely NO reprogramming of anything by anyone besides a trained Automotive Tech. And that goes for most of these supposed ASE mechs who don't know jack of what they're doing. I would ask him what exactly did he reprogram first, get the codes read and printed out then go from there. Cannot be done with a "generic" code reader. When you disconnected the 12v neg, (this resets all 5 ECU's) did you wait at least 5 mins before putting it back? What lights are on in the dash?
     
    #6 w2co, Mar 31, 2021
    Last edited: Mar 31, 2021
  7. prius-survivor

    prius-survivor New Member

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    Thanks for all the comments guys!

    @w2co: I should have waited longer when disconnecting the 12v. I waited only around 20-30s (wasn't using my head). After the diagnostic, no lights are on in the dash.

    @dolj: I ordered a new pump and will be replacing it myself. I was hoping there would be some code that is a dead giveaway. The CEL currently is not flashing any codes.

    I have techstream on my computer and can re-read the code myself tomorrow. Will update this thread again when I do!
     
    #7 prius-survivor, Apr 1, 2021
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