Complete shutdown while driving. ECU-IG fuse blown. Why??

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by rickster2, Jun 2, 2014.

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  1. nh7o

    nh7o Off grid since 1980

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    The fact that the coolant pump failure would sometimes blow that AM-2 fuse is the reason why the recall was made, as it is a real safety concern. Usually the pump just stops and the car overheats and goes into limp mode. The fact that you had the recall done already is a concern, but there are a very few others who have had more than one pump replacement as well. Perhaps something as simple as an inline fuse right at the pump body would be enough to prevent the worse failure mode.

    Maybe the third time is the charm.
     
    #21 nh7o, Jun 3, 2014
  2. rickster2

    rickster2 Junior Member

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    Thanks NH.

    Just got a call. Now they are confident that it is the "coolant storage pump."
    NOT the pump affected by the recall.
     
    #22 rickster2, Jun 3, 2014
  3. rickster2

    rickster2 Junior Member

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    And they will send the suspect coolant storage pump to toyota for analysis.

    When I pick the car up today, the service dept will show me their diagnostics (oscilloscope readings), but I am concerned again.

    One question is if this pump went bad enough to provide abnormal scope readings today, then why have they been able to test drive it (granted, short trips) since saturday?
    Maybe it is intermittent, but hopefully there is something definitive like it is now consuming way more current than it is supposed to, but not enough to trip the AM- fuse under test drive conditions.

    any thoughts?
     
    #23 rickster2, Jun 3, 2014
  4. JC91006

    JC91006 Senior Member

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    Does this explanation make you responsible for the bill?
     
    #24 JC91006, Jun 3, 2014
  5. rickster2

    rickster2 Junior Member

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    Yes. You'd think Toyota engineering would pick up this tab.

    It just doesn't seem right that ANY pump issue, should instantly, without warning, shut off your drive, power steering, power brakes and front panel displays.
     
    #25 rickster2, Jun 3, 2014
  6. JC91006

    JC91006 Senior Member

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    If they are making you pay the bill, the least you can do is file a safety report with NHTSA. Make sure this problem, if recalled, you would get your money back on the repair.
     
    #26 JC91006, Jun 3, 2014
  7. Former Member 68813

    Former Member 68813 Senior Member

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    Regardless who pays this should be reported to NHTSA. People die in incidents like this.
     
    #27 Former Member 68813, Jun 3, 2014
  8. nh7o

    nh7o Off grid since 1980

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    The coolant storage pump is not needed at all, in fact the EU versions do not have that system. It just means that there will be a longer warm up period without being able to re-use the left over warm coolant at the next start. So the car will work just fine without the pump, although it will show a check engine light. I would think that if the pump shorted sufficiently to blow the AM-2 fuse, it is a goner, a has been pump.

    This failure is rare, as the pump runs so rarely (starting and shut down only). It was the inverter coolant pump that got all the attention since it was common and ran continuously. But that makes it all the more strange, as the storage pump ought not to have been energized after the car had been running for some time.
     
    #28 nh7o, Jun 3, 2014
    SFO likes this.
  9. JC91006

    JC91006 Senior Member

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    That means if their diagnosis is incorrect, this will happen again........
     
    #29 JC91006, Jun 3, 2014
  10. rickster2

    rickster2 Junior Member

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    Thanks for all the inputs.
    I have the car back now. $409 cost.
    I will file a NHTSA report to make sure that this is documented.

    Regarding the diagnosis, I spent quite a bit of time with the service advisor (asst service mgr) and few minutes with their lead tech ("20yrs experience"). It sounds like dealers and Toyota take safety-related cases seriously, assigning a case number and an engineer.

    My Qs and the Dealer's paraphrased Answers:

    Q: You first thought it was the inverter pump. What changed your mind?
    A: The inverter pump did not measure abnormally as suspected, so they were directed to keep moving down the line of other items that load the 15A AM-2 fuse (yes, it was AM-2, not AM-1).

    Q: Why are you now so confident that it is indeed this coolant storage pump?
    A: The pump oscilloscope readings were way out of normal range. (I saw the printouts of the voltage waveforms. There was probably a 5-10X difference in amplitude between the two pumps). The Toyota case engineer confirmed that the pump was bad and the cause. Toyota indicated that they had seen past instances of this storage pump tripping AM-2, causing the symptoms described.

    Q: May 7th (4 weeks ago) you changed my coolant control valve assembly ($600) prompted by a check engine light. Was that related to this issue?
    N: No. Not in the same circuit as the AM-2 fuse.

    Note: I was focused on getting a definitive diagnosis and didn't think to ask if they replaced a good "coolant control valve assembly" May 7th and should have caught the "coolant storage pump" issue before the full system failure. I will follow up on this...
    -----


    You have to wonder why a a single (coolant storage) pump malfunction would shut everything down so dangerously? Shouldn't it just blow a dedicated fuse or just trip an indicator? Or did it trip an indicator, and they just missed the diagnosis May 7th?

    Anyway, the Prius is back and they convinced me that they found and replaced a responsible part.
     
    #30 rickster2, Jun 3, 2014
    Last edited: Jun 3, 2014
  11. rickster2

    rickster2 Junior Member

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    What about braking and steering if the AM-2 fuse blows again?

    Can I brake and steer indefinitely (without power steering and power brakes of course)?

    Or is the non-power-braking or non-power-steering reliant on some residual hybrid system power?

    We are taking on some mountain roads today and concerned.
     
    #31 rickster2, Jun 5, 2014
  12. edthefox5

    edthefox5 Senior Member

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    AM-2 fuse supply's B+ to relay IG-2 whose coil is controlled by Power Source Control ECU. That relay provides power to the cops (coil on plug spark plug ignitors). Thats it. It only supplies power to the cops. But that means the engine shuts off in this failure. You should still have limited hybrid power.

    If it was me checking this issue I would have thrown a DC Ammeter in place of the fuse and see how much current that circuit is pulling. Compare that to another G2. Reaching but may have a cop that's shorting out. I would also replace the spark plugs only because I want to pull the cops off and look at them. Your in there anyway. Check the cop connections to sparkplug really carefully for corrosion.

    Many corrosion issues where water has leaked over the water dam fell on top of engine and gotten into sparkplug well. Sometimes from people washing the car to aggressively and spraying water over the windshield dam.

    If it fails again I would replace all 4 cops.

    Has this car ever misfired? Has it ever thrown a misfire check engine light?

    I don't know about taking mountain roads until this is sorted out.
     
    #32 edthefox5, Jun 5, 2014
  13. nh7o

    nh7o Off grid since 1980

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    Note that the steering and braking both have mechanical linkages, so there is still control possible. People will always say they lost their brakes when the power assist goes, but the brakes are still there, just requiring more effort. In an emergency, it takes some real intention to press down hard on the brake pedal when one is so trained to just tap it lightly.
     
    #33 nh7o, Jun 5, 2014
  14. rickster2

    rickster2 Junior Member

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    Ed,
    There is some confusion perhaps if it was AM-1 or AM-2 fuse (the dealer finally said it was AM-2), and it did indeed shut down all power, the dash display, power steering and power brakes, window power too.

    Re the COPs, I've never heard any misfires.
     
    #34 rickster2, Jun 5, 2014
  15. JC91006

    JC91006 Senior Member

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    Here's hoping it's the coolant storage pump........I need mine recalled.
     
    #35 JC91006, Jun 5, 2014
  16. rickster2

    rickster2 Junior Member

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    OK, I think I am getting it. And it's not great news.

    Yes, Prius' "brake by wire" system does have a hydraulic (mechanical) system, but that too is controlled by electronics, and in the event of a system failure, it relies on a
    "backup power supply that uses capacitors to keep the braking computer and actuator operable even if the car loses power."

    more: ... When you push on the brake pedal, there is no direct connection to the actual brake pads the wheels. Instead, the pedal sends a signal to a computer, which decides whether the to activate the regenerative braking system, the actual disk brakes, or both.

    How the brakes on a Prius work – The Blogs at HowStuffWorks

    So, now my question is how long will the brakes operate (in non-power-assist mode) if this fails the same way again?

    I was just coming down some long hills, with no good place to pull off. If I know I only have a "few pumps" then I will pull over and ditch the car anywhere I can. If it's downhill and I have several minutes of reserve braking, I'll coast to a better spot.

    I can't believe I am even formulating this emergency plan.....

    On a related note, I need a better reason articulated, directly from Toyota as to why they are confident that this problem is solved. A second-hand verbal assurance that the Toyota case engineer is satisfied, isn't sufficient.
     
    #36 rickster2, Jun 5, 2014
  17. JC91006

    JC91006 Senior Member

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    I believe the paperwork that you received back from the dealership is the assurance they addressed your concern. They did tell you it was a serious issue and Toyota assigned a dedicated engineer to address the concern. I do believe the proper steps were taken in the diagnosis of the problem.

    If you fear your safety is at risk, I'm sure you can address this concern with Toyota HQ and they will offer you some type of discount to upgrade you to another Toyota.........It would be in their best interest to have this car off the road.
     
    #37 JC91006, Jun 5, 2014
  18. rickster2

    rickster2 Junior Member

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    They seemed to take this all very seriously and professionally, and a Toyota case number was assigned (and "closed"), but they offered zero explanation as to why this coolant storage pump (which I believe has it's own fuse) could blow that critical AM-2 fuse and create such a bad shutdown.

    The dealer did say Toyota had seen other cases of this pump blowing AM-2 / shutdown. This made me feel better the decision to replace that pump but it offered no assurance that it won't happen again.

    I'll ask the dealer about getting a more complete explanation. And if they can't help, Toyota HQ as you suggest.
     
    #38 rickster2, Jun 5, 2014
  19. nh7o

    nh7o Off grid since 1980

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    I believe this is incorrect, as far as I can see by looking at the brake system diagram. Someone chime in if this is not so.

    There is a mechanical action to the master cylinder that allows hydraulic pressure to be applied to the brakes. It just takes so much more foot pressure that people are convinced nothing is happening. I remember driving a friend's VW bug with unassisted brakes, coming from a big power brakes American car. I just about crashed because I was afraid to press so hard on the pedal, which from previous experience, I would have thought to be enough to lock the wheels and loose control.
     
    #39 nh7o, Jun 5, 2014
    Last edited: Jun 6, 2014
  20. rickster2

    rickster2 Junior Member

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    Thanks. No answers. Maybe I will start a thread just for the brake question.
    I still haven't been able to find anything about the hydraulics being connected to the pedal. Or info on how long the capacitor-based brake backup power supply lasts when the hybrid sys is shut off.
     
    #40 rickster2, Jun 7, 2014
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