Unusual Loud Beep on Start Up

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by SaulGoodeBrah, Jun 18, 2020.

  1. SaulGoodeBrah

    SaulGoodeBrah New Member

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    Location:
    Georgia, USA
    Vehicle:
    2007 Prius
    Model:
    ----USA----
    Now I know this is a common phrase on the internet and I've looked at plenty of posts regarding it, but none seem to match my situation. So let me explain:

    Occasionally, once I start the car there will be a loud, continuous beep, along with the ABS and brake system lights holding steady until the beep stops. Lasts only five seconds or so, but then the car drives perfectly fine afterwards. I have read that this beeping was usually associated with braking issues, but I have none. Brake pads probably need a replacement soon, but they aren't at the screeching level yet.

    A sidenote that is a big problem on its own: Sometimes my dashboard lights won't light up on start up and my back up camera won't work. Lights tend to come on only during hot days. Some research has gotten me to the conclusion that I need a new combo meter but don't know if/how it relates to this beeping problem.

    Other details:
    Toyota service department installed a new 12v battery last month. Combo meter problems were already an issue by this time however.
    OBD reader only came up with a P0420 code, which has only triggered my check engine light once and seems to be unrelated to the beeping.

    Any advice will be a tremendous help!
     
  2. edthefox5

    edthefox5 Senior Member

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    Vehicle:
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    May be the ABS bake actuator. Common very expensive failure item.

    Do you hear the accumulator pump motor constantly cycle on and off sounds like a rattle snake behind the dash?

    The dash going out is a very very common issue that unit is called the Combo meter. New rebuilt one costs $100 you install it. Not the reason your beeping that's the brakes are going to fail alert.

    Both off these issue discussions can be found by using the search forums tab up top and search the words I highlighted.
     
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  3. ChapmanF

    ChapmanF Senior Member

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    Vehicle:
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    IV
    The beep indicates the braking system hydraulic pressure is low and is not coming up as fast as it should while the pump runs. Could mean pump worn, valves not seating correctly, faulty relays or connectors powering the pump, etc.

    Your Gen 2 has the most brake-by-wire-y braking system that was ever sold on a Prius. Your foot on the pedal is strictly an input, and the computer and actuator do the braking. A disadvantage of that system is your foot will likely not feel anything very much different if you are braking normally/moderately, even during a warning that the pressure is somewhat low. But if you need to brake hard and the pressure is low, it won't happen.

    Gen 1 had a system with a boost chamber behind the master cylinder piston and Gen 3 brought it back, so in all the generations other than Gen 2, you are more likely to feel that the braking is harder when the pressure is low. But in Gen 2, you can be lulled into thinking it feels find, until the moment you want more than you've got.

    Some people go straight to opening their wallets, grabbing wrenches, and replacing expensive subsystems. An excellent post from just yesterday demonstrates how you may be able to save a real bundle by not skipping the part where you diagnose the problem.
     
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  4. SaulGoodeBrah

    SaulGoodeBrah New Member

    Joined:
    Jun 18, 2020
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    Location:
    Georgia, USA
    Vehicle:
    2007 Prius
    Model:
    ----USA----
    Yes, I get that sound all the time, honestly I thought it was normal to hear it. Thank yall for the references and knowledge!
     
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