Intermittent hybrid warning light

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Naurill, Aug 3, 2018.

  1. Naurill

    Naurill Junior Member

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    115k miles, 2007, relatively new (12 months old) 12V battery, long period (12+ weeks) of dry 30C weather... and today I got the red triangle of death and the hybrid system warning light. The car being well maintained, with replacement (recall) coolant pumps and the like and nothing obviously wrong and a skeptical of the advice in the owners' manual, I decided to drive the car from work a few miles. After all the main Toyota dealership was down hill and about 5 miles away. The power, fuel consumption, sound, feel and smell of the car was normal. Could it be the inverter coolant pump -- a worry and I had only checked the fluid levels.

    Well I got half way there and hit a red light. I took the opportunity to stop the engine and restart the car to see if the red triangle of death and hybrid system warning light on the MFD reset.. alas no, it did not.

    Yet, the inverter had not melted and the car was only a few miles from home. I pressed on. When I arrived, I stopped outside the house, stopped the engine and nipped into the house to ask my wife (nicely) to move her car out of the garage to allow me to do some diagnostic checks in the garage. She kindly obliged (I am a lucky guy).

    Of course in the two minutes that that took, when I restarted the car there was no red triangle of death or hybrid warning light.

    I will check for regular codes with an non-Toyota OBDII diagnostic, but expect to find nothing. I will check for water in the 12V battery well (again), but at first sight that did not seem to be a problem.

    Any ideas, please? (Many thanks in advance).

    Naurill
     
    #1 Naurill, Aug 3, 2018
    Last edited: Aug 3, 2018
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  2. hchu1

    hchu1 Active Member

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    Yes, knowing the codes would help you pinpoint the issue. Til then, look in the inverter coolant reservoir check for proper fluid level. Next, without pressing on the brake push on/off button twice, check the inverter coolant fluid for movement. If no movement, dead inverter pump, replace before driving too much more. Frying your inverter is very expensive new OEM, or less expensive used from a salvage yard. Good luck.
     
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  3. Naurill

    Naurill Junior Member

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    Thank you hchu. I'll try that over the weekend and check the OBDII codes and go from there (and post). N
     
  4. wjtracy

    wjtracy Senior Member

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    Expecting AGM 12v with no need to check water level.
     
  5. Naurill

    Naurill Junior Member

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    ...? Sorry, I don't follow you. Please explain! N
     
  6. Naurill

    Naurill Junior Member

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    Oh, I get you. Water ingress into the battery well previously caused problems with this car, but it is dry, since the repair I made -- not the problem this time.
     
    #6 Naurill, Aug 4, 2018
    Last edited: Aug 4, 2018
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  7. Naurill

    Naurill Junior Member

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    No codes and the fault did not reappear today. The oil was a bit low, but I think that is coincidence. There is some movement in the inverter coolant reservoir, but it does not seem great, so it might be the coolant pump about to fail. I will get it changed in case (can't do any harm).

    Also. the 12V battery is 12.5V at terminals, connected with ignition off.

    The triangle and hybrid light are now back, following a short drive when they did not come on, a few minutes with the ignition off and then back on after a few 100m on the next short journey (aborted). Still no code on my generic reader, but it hints that there are 4 more advisory codes. I will ask the dealership to take a look and unless there is evidence to the contrary, change the inverter coolant pump, coolant, thermostats, and water pump. Then if it proves to be the battery the car will be set for a new one and another 100k miles!
     
    #7 Naurill, Aug 4, 2018
    Last edited: Aug 4, 2018
  8. wjtracy

    wjtracy Senior Member

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    The only other thing I can think could be clogged HV Bat cooling fan
     
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  9. Naurill

    Naurill Junior Member

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    Thanks. I thought of that, but only checked it about 12 months ago and it was perfect and I cannot think of any reason (e.g change of vehicle use) that would have clogged it in a year when 10 years of use did not.
     
    #9 Naurill, Aug 4, 2018
    Last edited: Aug 4, 2018
  10. JC91006

    JC91006 Senior Member

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    I'm almost certain you have a failed inverter pump. You can also check your oil level to make sure it's not low

    You can easily check this by opening the cap to your inverter coolant reservoir and see if there's turbulent movement in the liquid when the car is READY. No movement would suggest the pump has failed.

    Although the recall has been completed (probably many years ago), these pumps will fail again.
     
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  11. wjtracy

    wjtracy Senior Member

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    ...wow extra credit you can rule that out
     
  12. Naurill

    Naurill Junior Member

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    Many thanks. There is movement in the inverter coolant, but compared with YouTube videos of new pumps it is not much movement. I agree with you JC91006 it does look like the pump is on the way out. The dealership is 5 miles away and the car is booked in for Friday. Russian roulette to drive there? N
     
  13. johnjohnchu

    johnjohnchu Member

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    I drove my car slowly to a dealership 25 miles away for inverter pump fix. It is best to do it in the early morning when air is cool. Also defective inverter pump, hence over heated inverter will deactivate A/C.
     
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  14. Naurill

    Naurill Junior Member

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    A couple of days ago, I called out the breakdown service with the idea that they would tow me to the dealership this morning, but there was a truck about a mile away when I called and he arrived immediately, Of course when I started the car there was no warning light and his diagnostics did not pick up any Toyota DTCs. His company policy was not to touch any hybrid element of a vehicle, so we agreed that I would drive the car to the dealership this morning and only call the breakdown service if a warning light lit.

    I dropped the car into the dealership (~5miles away from home) this morning with no repetition of the warning light. I await with keen anticipation to hear what the technician finds. More soon...

    Ah, the phone rang as I was typing and I have had a chat with the technician.

    DTCs include historical: P3000, P3110, current: U0129, C1377, C1378, U0123, U0124, U0126, U0293, and B1421. The problem seems to relate to the speed control ECU and braking system (and brake main capacitors). The tech said that braking in reverse seemed weak, but after he drove the car around the block that issue went away. He is going to do an hour's worth of diagnostics around the speed control ECU cables (visual and voltage checks). He also will look at the inverter coolant pump. Grateful for thoughts and any diagnosis based on the codes.
     
    #14 Naurill, Aug 10, 2018
    Last edited: Aug 10, 2018
  15. Naurill

    Naurill Junior Member

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    Seems really similar to this thread OBD2 DTC Codes research | PriusChat

    Unfortunately, that thread does not have a conclusion, but the posts seem to indicate either a 12V battery problem or a relay/muliplexer problem and that the fault will be hard to diagnose.
     
  16. Naurill

    Naurill Junior Member

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    The dealership did not find any faults and have said I can collect the car. It is 15C cooler than when the fault originally occurred, which might mean something. (I have ordered an Toyota friendly OBDII thingy, more soon perhaps).
     
  17. Naurill

    Naurill Junior Member

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    Analysis of possible faults:

    1. Low oil -> Red triangle of death, but this should not have caused the hybrid system warning light. May or may not have triggered this. Does not look as though it caused any significant damage. But I might learn more on a long/hot drive.
    2. 12.5V aux battery, could (just) explain codes and red triangle of death. hybrid system warning light and codes.
    3. Previous faults and my home installation of a used Brake Control Power Supply Module (18 months ago) could account some or all of the codes as I neither disconnected the battery nor cleared the codes after my fix (yet the orange brake warning light did go out after the fix and a new fuse).
    4. The inverter coolant pump could be failing, but the tech did not buy that theory, yet the dealer was happy to quote 'large' to replace it.

    So, I have topped up the oil. I have checked all the other coolant levels. I will run the car for a week on modest journeys and if the fault does not repeat I will invest in a a new inverter coolant pump, and a new coolant pump. Not sure the course of action if I get another fault. Perhaps back to another dealer for a second opinion (and perhaps a pump).

    My cost analysis tells me that these repairs are commensurate with the long term depreciation costs of the car and I would like to max out its life (within reason).

    Grateful for thoughts, please.
     
  18. Naurill

    Naurill Junior Member

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    20 miles yesterday and 200 today in rain with headlights, etc. on and no warning light -- looking good.
     
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  19. Naurill

    Naurill Junior Member

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    No trouble this week during routine commute. New pollen filter.
     
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  20. Naurill

    Naurill Junior Member

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    Cleared MFD codes.
     
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