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12V good. Fusable Link Good. Am2 Keeps blowing. ICP disconnected.

Discussion in 'Gen 2 Prius Main Forum' started by lmarcucci, Jul 19, 2015.

  1. lmarcucci

    lmarcucci Junior Member

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    Hi everyone,

    Customer's car died about 2 hours from me. Does anyone know off the top of their heads, what this could be? It is at a shop now, and i walked them through how to test the main fusable link in the engine bay, and they said it was good. They also checked the 12v battery and that tested good. Here is what happened.

    The customer was driving, then he said the triangle of the death and check engine light came on. Then, he kept driving for a little while and then all the sudden everything went dark and he coasted to the shoulder. The car hasnt had the inverter coolant pump recall done, so i am leaning towards that. The car's dome lights come on, the key can unlock and lock the car, but if you slide the key in and press the power button, nothing happens. What on earth would cause that? Thanks!
     
    #1 lmarcucci, Jul 19, 2015
  2. Beachbummm

    Beachbummm Senior Member

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    is the orange safety plug still seated correctly?
    check the 12 volt ground connector at the body.
     
    #2 Beachbummm, Jul 19, 2015
  3. lmarcucci

    lmarcucci Junior Member

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    Ended up being the AM2 fuse like the lucious garage posts says. Inverter coolant pump caused it.
     
    #3 lmarcucci, Jul 19, 2015
  4. Beachbummm

    Beachbummm Senior Member

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    they know their stuff...
     
    #4 Beachbummm, Jul 19, 2015
  5. lmarcucci

    lmarcucci Junior Member

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    I spoke too soon. The inverter coolant pump is disconnected now and the am2 fuse is still blowing. What could it be? CHRS pump?
     
    #5 lmarcucci, Jul 19, 2015
  6. bisco

    bisco cookie crumbler

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    are there any codes?
     
    #6 bisco, Jul 19, 2015
  7. lmarcucci

    lmarcucci Junior Member

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    I suppose a good way to find out is if I plug a scanner in when it is in ACC mode. The mechanic did not do this. I will have to drive 2 hours tomorrow and fix it myself. I offer warranties on my hybrids, so I have to do what I have to do. Could the wires actually have gotten so bad leading to the inverter coolant pump that they melted together and unplugging it did nothing? That's the only other thing I can think of. What else is on the AM2 fuse that would blow like that?
     
    #7 lmarcucci, Jul 19, 2015
  8. bisco

    bisco cookie crumbler

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    according to patrick wong in another thread, the am2 fuse covers engine control, ignition, interior light, push button start system, hybrid vehicle immobilizer system, shift control system.
     
    #8 bisco, Jul 19, 2015
  9. lmarcucci

    lmarcucci Junior Member

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    I saw that. I'm just going to do the trial access to the TIS. I'll post here if I fix it.
     
    #9 lmarcucci, Jul 19, 2015
    Last edited: Jul 19, 2015
  10. bisco

    bisco cookie crumbler

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    thanks, all the best.(y)
     
    #10 bisco, Jul 19, 2015
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. A short in the inverter coolant pump is the most likely cause of a blown AM2 fuse. Is it possible that the tech you were working with is unclear about the location of that pump (behind the driver's headlight assembly)?

    2. If the pump was disconnected and the AM2 fuse continues to blow, you could pull the IG2 relay to see if the fuse blows or not. Depending upon the answer, that would narrow down the short to the wiring which receives 12V from the AM2 fuse even when the relay is open - or the wiring that receives 12V power via the IG2 relay.

    3. If the AM2 fuse continues to blow with the IG2 relay removed, pull the INV W/P relay to see if that makes a difference. If it does then the wiring from the relay to the pump has a short.

    4. If the AM2 fuse continues to blow with the IG2 and INV W/P relays removed, maybe the Power Source Control ECU has failed or there is a fault in the wiring between the fuse and those two relays.

    5. The CHRS pump is not a suspect as it has its own 10A fuse for overload protection and does not receive power via the AM2 fuse.

    6. The fuel injectors receive 12V power via the AM2 fuse and the IG2 relay - so that is a potential area to investigate if the fuse only blows when the IG2 relay is installed. When the car is IG-OFF and the injector wiring harness connector is removed, measure the resistance of the terminals at the injector to ground, which should be infinite. Also measure the resistance of each injector wiring harness connector terminal to ground. The resistance measurement should be high because one side of the injector receives 12V power while the other side connects to the engine ECU which pulses the injector ground connection.
     
    #11 Patrick Wong, Jul 20, 2015
    Last edited: Jul 20, 2015
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  12. lmarcucci

    lmarcucci Junior Member

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    Patrick, thanks for your help. Where in the world is the Inverter water pump relay and IG2? My TIS is showing that the IG2 is in the inner circuit of the engine compartment fuse box and same goes for the inverter pump relay, but in the interior fuse box. Do I need to remove the boxes to get to the umderside or what?
     
    #12 lmarcucci, Jul 20, 2015
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Actually, it looks like my suggestion to pull relays is going to be very difficult to implement.

    The IG2 relay is part of the Unit B relay assembly in the main relay/fuse box. Unit B actually contains four relays as well as four fuses, one of which is AM2. You would have to be very persistent to pull that relay since you would have to short the switched terminals of the other three relays when you pull Unit B and figure out how you would implement fuse protection for the four circuits.

    The INV W/P relay appears to be unsocketed and probably is soldered directly to a circuit board in the relay box under the instrument panel. So that also will not be easy to remove.

    An alternate approach would be to physically cut a wire to break the relay connection - if you get desperate and cannot think of another troubleshooting method. Then you could repair the cut by soldering and using heat shrink tubing to insulate the soldered connection.
     
    #13 Patrick Wong, Jul 20, 2015
  14. lmarcucci

    lmarcucci Junior Member

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    Patrick, I have my bags packed for tomorrow. All I had to do was use my brain and a spare parts Prius to figure out. Like seconds after I posted that. The B section of the fusebox in the engine bay is an integrated relay/fuse contraption. It comes out and is connected is the back. IG2 is integrated inside of it.

    The inverter water pump relay is integrated into the driver side intrument panel junction box. There's a 4 pin connector , with 3 pins in use. I suspect that is the connection to the relay. The colors seem to match up.

    There's a "short connector" for the inverter water pump using a single white/black stripe wire above the fuse box and beside the inverter. I'll see if that helps finding the short.

    But, I am bringing with me the whole driver junction box and integrated relays/fuses. So, I should be good.

    Thanks for your help
     
    #14 lmarcucci, Jul 21, 2015
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  15. lmarcucci

    lmarcucci Junior Member

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    The tech I was working with over the phone pulled the fuse after he pulled the connector to the inverter water pump. I connected my multimeter to the pins on the water pump and it was competely shorted. I pulled the blown fuse and replaced it when the inverter pump was unplugged. Then the car drove fine to the toyota where they did the recalls and now the car drives perfectly. But, interesting enough, even when the car was off, i heard the relays clicking when i put the good fuse in immediately.
     
    #15 lmarcucci, Jul 21, 2015
  16. bisco

    bisco cookie crumbler

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    so post #5 was incorrect?
     
    #16 bisco, Jul 21, 2015
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