No start, no lights on dash

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Merk_rr, Mar 7, 2025 at 4:19 PM.

  1. Merk_rr

    Merk_rr New Member

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    Hey guys, picked up a 2005 prius that wouldn't start. No lights are on the dash at all except door ajar light. No MFD.

    When I go to start it and press the power button, the orange power light comes on for a second along with green parking light, then turns off. I can hear a relay click on then off quickly nearby the cabin fuse panel.

    I have a brand new 12v installed, checked the fuses at the 12v connection, the fusible link and all the fuses with everything looking good.

    Any ideas on what else to check? Headlights, brake lights, dome light all work. I can also hear the brake actuator kick on
     
    #1 Merk_rr, Mar 7, 2025 at 4:19 PM
  2. Tombukt2

    Tombukt2 Senior Member

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    Sounds like you may have the battery isolation fault. You're locked out of the system The relays won't click open they immediately close back up because high voltage from the battery is leaking somewhere this is just a guess but I've had it two or three times. You may not even be able to read the code You might if you put it in the accessories mode so if you sit in the car and don't touch the brake and push the button once remove your finger and then push it again without the break all the dash lights should light up Is this so? If so then you need a capable scanner like an AP200 so you can get the code and probably the subcodes
     
    #2 Tombukt2, Mar 7, 2025 at 10:06 PM
  3. Merk_rr

    Merk_rr New Member

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    Hey thanks for the reply, but even with trying to go into accessory mode nothing changes.
     
    #3 Merk_rr, Mar 7, 2025 at 11:06 PM
  4. dolj

    dolj Senior Member

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    Does this mean you only checked fuses at the battery? And when you say, "They all looked good," do you mean you only visually inspected the fuses? If yes, you really need to use an ohmmeter to check fuses for continuity.

    Have you checked the fuses in the engine bay on the LH side, especially the AM2 fuse? If the inverter coolant pump shorted out that will blow the AM2 fuse which will make the car inoperable.
     
    #4 dolj, Mar 8, 2025 at 3:38 AM
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  5. Merk_rr

    Merk_rr New Member

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    Sorry, should have specified, I checked all the fuses under the hood, under the dash and by the 12v with a multimeter. They all show continuity. I'm only getting the clicking from the relay under the dash , not the hv relays in the back that you would typically hear
     
    #5 Merk_rr, Mar 8, 2025 at 8:27 AM
  6. Merk_rr

    Merk_rr New Member

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    I've read many posts with similar issues and found that I need to look at the power source control ecu and to make sure I have power going to it. I checked pins 12 and 33 and only have power at pin 12 (12 is power from am2, 33 is am1). I checked the fuse panel under the driver side dash and located fuse for am1, which tested fine with a multimeter. Also checked for power at this location and found no power.

    I've read that am1 is supposed to have constant power but also read that only 04 has the am1 fuse and the later years they did away with it? (Mine is 05).

    What would cause am1 to not have power? Am2 fuse is good
     
    #6 Merk_rr, Mar 8, 2025 at 11:55 AM
  7. Tombukt2

    Tombukt2 Senior Member

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    So you have no clicking at the rear relays at all then you're not even booting or attempting to boot the car I mean you are but the car is having none of it so it's like you're locked out kind of what I was getting at but maybe not I would quickly do the down and dirty test on the high voltage battery safety plug with the cover off and your test meter set for DC volts and you touch one of the silver screws on the plug and touch the ground or a bolt going through the battery case It should count down to zero if it stops at 70 80 90 110 volts whatever the battery is not isolated and voltage is leaking over to the frame of the car which is your 12 volt grounding point Not good if that's what's happening and testing what I'm talking about will rule that out quickly. It was just a thought The symptoms seem very similar I've had this problem twice in two different generation twos
     
    #7 Tombukt2, Mar 8, 2025 at 12:22 PM
  8. dolj

    dolj Senior Member

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    The repair manual (RM) for the 2006 shows an AM1 fuse, I doubt they got rid of it in the 2005 model and then brought it back. But never say never. I'd check the 2005 RM/wiring diagram so you don't end up chasing your tail.

    You can find info on how to get RM and wiring diagram info in this wiki page.
    Good old-fashioned troubleshooting using the wiring diagram.
     
    #8 dolj, Mar 8, 2025 at 9:06 PM
  9. Merk_rr

    Merk_rr New Member

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    Ended up being an easy fix even though I tore the whole dash apart lol. I found the am1 fuse was in the wrong spot. Thanks for all the replies
     
    #9 Merk_rr, Mar 9, 2025 at 7:10 AM
    Brian1954 and ColoradoCrow like this.
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