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Master Warning Light/Hybrid System Warning

Discussion in 'Generation 1 Prius Discussion' started by panache, Jul 2, 2009.

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  1. panache

    panache New Member

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    Location:
    Staunton, VA
    Your Vehicle Year:
    2002 Prius
    Model:
    N/A
    Let me introduce myself: I am a "new" owner of a used 2002 Prius which I bought 3 weeks ago from someone I found on Craigslist. I had the car inspected by a local shop (not the dealer as the dealership was too busy and time was critical). They said the car was OK except for the spark plugs having a bigger gap than normal and may need to be replaced soon. They did not check the hybrid battery or electric motor as they were not qualified for that. The hybrid system had just been serviced 5000 miles ago under warranty with a new battery installed so I did not think it would be an issue.

    Today, I drove to lunch (about 1 mile away) and after lunch the master warning light came on, along with on-screen icon saying the hybrid system had a fault (the car icon with the exclamation mark through it). Also, the check engine light on the dash came on.

    I was puzzled and shut off the engine and started it again. The warning came back but I had to be back at work so I decided to drive back. Everything seemed fine, the car drove normally and I did not hear any sounds or other abnormal behavior. I called the dealership and they were busy until Monday and they said if the car seems to be driving normally I can keep driving a little as necessary.

    When this happened, I only had one dot of gas remaining in the tank (the last dot before the low gas alarm goes off) and it was my intention to go fill up on the way home.

    After work, I started the car up again and the same error message/check engine light came back on. I drove 1 mile to the gas station, filled up and after filling up all warnings and lights went away. I drove home (30 miles on the freeway) and ran a few errands this evening and everything seems normal, no faults or warning lights. It seems that filling up took care of this?

    Should this be something I should have checked out or was this just because of the low fuel level?

    Thanks in advance for any advice.
  2. bwilson4web

    bwilson4web 03 and 10 Prius

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    Location:
    Huntsville AL with 2003 Prius
    Your Vehicle Year:
    2010 Prius
    Model:
    III


    If you have a temporary problem, the alarm will light and stay on for three restarts. If the problem goes away, so too does the error light. You did three restarts, clearing the alarm light. However, the original error code remains.

    There is a fairly common problem with a sticky throttle plate that can easily be fixed. Mine first happened about two years ago to my 2003 Prius. Since then, I clean the throttle plate once a year and the problem has not come back.

    Bob Wilson
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  3. panache

    panache New Member

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    2002 Prius
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    Thanks for the info. I did bring it to the AutoZone and the computer stored a code P3191. Apparently this may be related to the sticky throttle plate so I will try and get that cleaned.
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Location:
    Green Valley, AZ
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A
    DTC P3191 is an engine no-start trouble code. Cleaning the throttle plate and throttle body interior will help. Also, make sure that the engine oil is 5W30 and not overfilled.

    Since you know the iridium spark plugs are marginal I suggest that you also replace them now, using the correct NGK or Denso plugs which will cost ~$12 each. (Please resist using some cheap alternative, especially if not iridium.)

    After you've replaced the spark plugs and cleaned the throttle body assembly, if you still get DTC P3191 then I recommend you replace the engine ECU with the current version. I've previously posted TSB EG011-03 and this document provides the part number of the current version ECU.
    1 person likes this.
  5. Sandy

    Sandy Hippi Chick

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    Ocala,Fl
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    Other Non-Hybrid
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  6. panache

    panache New Member

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    Location:
    Staunton, VA
    Your Vehicle Year:
    2002 Prius
    Model:
    N/A


    It's been two weeks now since I changed the spark plugs and had the fuel system cleaned and no problems again, and also gas mileage improved to 50 mpg!

    Thanks for the advice Patrick and Bob!
  7. tochatihu

    tochatihu Senior Member

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    Location:
    Kunming Yunnan China
    Your Vehicle Year:
    2001 Prius
    Have you still got the old plugs? I'd appreciate closeup photos of the ground electrodes. They may be pitted.
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