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Vehicle Proximity Notification System Elimination (Sorry Blind People)

Discussion in 'Gen 4 Prius Accessories and Modifications' started by lohikaarme, May 5, 2017.

  1. lohikaarme

    lohikaarme Troll

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    There have been quite a few threads started by people wanting to eliminate the proximity warning system: That annoying electronic buzz produced from a speaker mounted in the grill to warn people a hybrid is coming. The issue at hand, however, is that unlike the GenIII, by unplugging this speaker it will throw a fault and a yellow triangle will appear when you start the vehicle advising you to have the proximity sensor checked!

    There was at least one thread there someone modified their speaker by breaking it and soldering in some components. There was another thread with someone adding foam in there speaker to silence it. This thread is to show there is a better way.

    First a diagram from the service manual referencing the speaker:

    upload_2017-5-5_20-28-54.png

    So the key is to have resistance between 6.4 and 9.6 ohms to make the system think everything is good.

    But what about watts? How do you know what resistor to buy?

    I am not an EE but here are the formulas:
    There is no direct calculation of ohms to watts. First you need to calculate ampere:

    Volt / Ampere = Ohms

    The voltage will be Correction Here it is 6volts DC going to speaker not 12volts, for the sake of this I will select 8 ohms so 6/A=8. A = .75
    Now that you have ampere you can calculate watts. The formula is:

    Volts X Ampere = Watts

    So 6 X .75 = Watt. Watt = 4.5
    So the perfect way to fake the system is to introduce a 4.5Watt 8Ohm resistor

    Now lets get into the hardware. I bought 3 components for this modification:

    I originally bought an oversized resistor based on using 12VDC instead of 6VDC. As a result I had to loop back and order the right size to complete this.

    However, below are the exact part numbers for the Toyota connector that will plug into the engine harness, and the terminals that plug into the connector. Once the resistor arrives I plan on attaching this to the terminal leads which should complete the build.

    I did try this with the oversized resistor and can confirm that there are no warning lights on the dash so it will work.

    upload_2017-5-5_20-37-12.png

    upload_2017-5-5_20-37-36.png

    Picture below is using the oversized resistor.

    upload_2017-5-5_20-39-7.png
     

    Attached Files:

    #1 lohikaarme, May 5, 2017
    Last edited: May 6, 2017
  2. ChapmanF

    ChapmanF Senior Member

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    Generous partial credit since you say you're not an EE, but "the voltage will be 14 volts" sounds like you're assuming the speaker drive signal is the same as the car's DC power voltage. The signal is going to be an AC waveform, and you could probably save some expense in your design by just holding an AC RMS meter to it while it's operating, to see what the voltage really is.

    How big is the OEM speaker? Does it look anything like a 25 watt capable speaker?

    As another cause for rethinking, if you wrap up a 25 watt resistor all in vinyl tape like that, and then put anything close to 25 watts into it, it will be rid of that tape in no time. :)

    -Chap
     
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  3. lohikaarme

    lohikaarme Troll

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    there is a picture of the speaker next to the resistor in this thread. If the resistor needs to be changed I am hoping an EE will chime in. The real key to this thread is that it includes the exact Toyota part number for the connector that mates with the engine harness and the terminals for the connector to allow a speaker bypass.

    upload_2017-5-5_22-25-51.png
     

    Attached Files:

  4. alanclarkeau

    alanclarkeau Senior Member

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    There was discussion on the early post about whether this was in fact a legal modification. I can't remember the outcome.
     
  5. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Lawyers are going to love him, "You mean that the reason my client did not hear your car was you deliberately deactivated the alarm to protect pedestrians?"
     
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  6. lohikaarme

    lohikaarme Troll

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    I will take the legal chance-
    I measured the voltage at the harness it is 6volts.

    So knowing the voltage and the resistance needed the rest of the calculations are as follows:
    This will need a 4.5W 8Ohm resistor

    upload_2017-5-6_0-7-32.png
     
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  7. lohikaarme

    lohikaarme Troll

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    Update:

    After much research I decided to go with the resistor I have. It is vastly oversized at 20W but even in the case where the wattage needed to dissipate is 4.5W, you would typically double that so you would need 10W. The wattage is the amount of energy that the resistor can dissipate without damage. The problem appears to be in using vastly oversized resistors is that the tolerances open up with greater swings. The range being 6.4 - 9.6 Ohms and using an 8 Ohm resistor there is a lot of play here so the tolerances can be vary quite a bit.

    As far as heat, after hooking everything up (leaving the resistor exposed rather than with electrical tape), I went on a five minute drive and touched the resistor. As cool as a cucumber so I am quite sure this will be fine.

    Finally onto the legal argument of hitting someone and there being a question on if this was working. People, if you hit someone you are screwed. It does not matter if you have a noise maker or not you are not getting out of it. The pedestrian is always right. You are to maintain control of your vehicle at all times. You will never win the argument of "I hit him but the noise maker should have alerted him I was there". Disabling this I suspect could be classified as an equipment violation such as tinting windows darker than the state allows, lowering your car, putting a shaded plate over your license plate etc. The government mandated that > 2012 hybrids need a sound maker, the risk is more not meeting a standard not a way out of running someone over.
     
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  8. randomwalk101

    randomwalk101 DYI'er

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    ....or you can hook up Trchstream and turn the volume all the way to the lowest level and it's virtually silence.
     
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  9. bisco

    bisco cookie crumbler

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    can someone record the lowest level outside the car please?
     
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