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Master Warning Light

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by coachfdm, Jun 12, 2009.

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  1. coachfdm

    coachfdm New Member

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    Location:
    Maine, USA
    Your Vehicle Year:
    2005 Prius
    Model:
    N/A
    My '05 Prius has 83,000 miles on it. A few days ago my wife said that the master warning light (the red triangle with the exclamation point in it) came on about 8 minutes into her drive to work. We live in Maine and the outside temp was in the 60's. She drives less than 10 miles to work over roads that stay under 50mph. She keeps her key in her purse.

    The light has come on for her four separate times. Steady light, no flashing. It has not happened for me, we have separate keys. I brought it to our selling dealer about an hour away yesterday, and it did not come on for me, but we did need to replace a leaky water pump. This morning at about 8 minutes into her drive, the light came on again. She called me, I had her put the key in the slot, shut off the vehicle, restart it and the light came back on.

    The dealership ran a scan, and did not come up with anything to report. They did see something in the remote start computer code history, but nothing conclusive... Any ideas?

    Thanks
  2. jdenenberg

    jdenenberg EE Professor

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    Location:
    Trumbull, CT
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A


    You will get a harsh warning if a door is opened without your Prius being in "Park" and no code is set. So one possibility is that either a door (or the hatch) is not closing properly or you have an intermittent switch on one of the doors (or hatch). Note that in this case the MFD has a nasty message on it that you can see by opening the door (preferably while stopped) with your Prius not in Park.

    Another possibility is a weak remote battery, but I don't have the fancy remote system so I can't be certain of its behavior as the remote battery weakens.

    JeffD
  3. richard schumacher

    richard schumacher shortbus driver

    Joined:
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    Location:
    United States
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    Push any button on the fob. If the red LED on the fob does not light replace the fob battery.

    Test the 12V battery. With the car off it should read at least 12.5V at the jump point under the hood. Or, use JeffD's selftest procedure (no tools required):
    Checking 12v Battery Health - Hybrid Car Forums

    An hour is a long way to go for service. Is there not a closer dealer?
  4. firepa63

    firepa63 Former Prius Owner

    Joined:
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    Your Vehicle Year:
    Other Hybrid
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    I don't think a weak fob battery could cause the warning light observed. It could be a door not being closed tight or a faulty door switch.
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