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Extended beep and circular yellow exclamation light comes on at startup, brakes don't work

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by paulisme, Jun 11, 2009.

  1. paulisme

    paulisme New Member

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    A couple days ago I turned on my 2004 Prius, and when I put it in reverse, a loud, extended beep sounded and a yellow circle with an exclamation point in the center came on. Of course I immediately hit the brakes, but the brakes had no power and barely were able to stop the car. I turned the car off and back on again, and the same thing happened. I again turned the car off and back on again, but this time no beep, no warning light, and the brakes had power again. I was able to drive it home that day, but the next morning the same thing happened. Being afraid to drive it, I had it towed to the local Toyota service department. They ran a diagnostic on it, and $134 later, they said it was only due to a low charge in my auxiliary battery. I went and picked up the car, drove it home, and everything seemed fine. When I went to turn it on this morning, there it was again. Same beep, same warning light, same remedy (turn it off, on again, off again, on again). This time I drove it to work, and here I sit wondering if it's safe to drive home. I called the Toyota service center and they said they'd look at it again for no charge, but I'd like to have an idea of what could possibly be wrong before I take it in. Has anyone else experienced this?

    Note that this light does not look like the "low tire pressure" light on the later Prius models (my wife has a 2009 Prius so I've seen that light before). Unlike the low tire light, this light is a perfect circle (no ripply tire tread line at the bottom).
     
    #1 paulisme, Jun 11, 2009
  2. firepa63

    firepa63 Former Prius Owner

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    Did they replace the battery or just charge it? If the battery is the original battery, it has probably reached the end of it's useful life and cannot hold the charge. It's time to get a new battery. If you get the battery from the same dealer that "charged" it, ask them to credit the $134 towards the cost of the battery replacement.
     
    #2 firepa63, Jun 11, 2009
  3. paulisme

    paulisme New Member

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    They just charged it. I had the battery replaced about a year ago, so there should be no problems with it. The service center also ran a diagnostic on the battery and everything checked out. I remember when my original battery went bad, it the car didn't behave this way at all.
     
    #3 paulisme, Jun 11, 2009
  4. Mike Dimmick

    Mike Dimmick Active Member

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    This yellow light is the Brake Control Warning Light. The service manual says, "informs driver when there is trouble with ECB or problem with brake system that has no influence on driving, by turning on." There is also a red BRAKE idiot light that warns of more serious problems. (In Canada and elsewhere, this light has the same shape as the Brake Control Warning Light but is red.) The dealer are supposed to check the Skid Control ECU for stored DTCs.

    I suspect it could be DTC C1256/57, Accumulator Low Pressure. The specified procedure is to check that the pump motor's electrical resistance is as expected (if not, replace the brake actuator assembly), check that the accumulator pressure sensor is reporting good pressure after pressing the brake pedal several times to use up then repressurize the accumulator (again, replace the actuator), and if that seems OK, replace the Skid Control ECU.

    Neither's going to be cheap: the Skid Control ECU is $1,658.50 (MSRP) and the accumulator $1,857.53. Prices from Champion ToyotaWorld, with my guess that the accumulator is described as 'modulator valve'. Well, that's one of its functions.
     
    #4 Mike Dimmick, Jun 11, 2009
    1 person likes this.
  5. paulisme

    paulisme New Member

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    Wow, that's not good news. Is it even safe to drive the car before I get this fixed?
     
    #5 paulisme, Jun 11, 2009
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    You'll have to decide whether it is safe to drive the car or not. Since you have a brake system problem I'd recommend you have the car towed.

    Although a weak 12V battery might be part of the problem, I doubt that is the cause of the brake issues you've noticed.

    Good luck.
     
    #6 Patrick Wong, Jun 11, 2009
  7. paulisme

    paulisme New Member

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    I'm having it towed. The dealership decided to pick up the tab.
     
    #7 paulisme, Jun 11, 2009
  8. firepa63

    firepa63 Former Prius Owner

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    Let us know what they find as the problem.
     
    #8 firepa63, Jun 11, 2009
  9. paulisme

    paulisme New Member

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    Well, I got the call from the service center. The advisor said it was the Skid Control ECU like Mike suspected. He quoted me a price of around $1,700. He's calling the dealer where I bought the car to see if I had the extended warranty (I don't remember if I got it or not), so we'll see.

    Thanks for the advice, guys.
     
    #9 paulisme, Jun 12, 2009
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If you can DIY an alternative would be to buy a skid control ECU taken from a salvage vehicle, then install it yourself. Might cost you several hundred $s.

    This ECU failed in my dad's 2007 and was replaced under warranty. Failure of this ECU is uncommon but still happens as you can now attest.
     
    #10 Patrick Wong, Jun 12, 2009
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